Interaction of surface water and groundwater in the Nile River basin: isotopic and piezometric evidence

NASA Astrophysics Data System (ADS)

Kebede, Seifu; Abdalla, Osman; Sefelnasr, Ahmed; Tindimugaya, Callist; Mustafa, Osman

2017-05-01

Past discussions around water-resources management and development in the River Nile basin disregard groundwater resources from the equation. There is an increasing interest around factoring the groundwater resources as an integral part of the Nile Basin water resources. This is hampered by knowledge gap regarding the groundwater resources dynamics (recharge, storage, flow, quality, surface-water/groundwater interaction) at basin scale. This report provides a comprehensive analysis of the state of surface-water/groundwater interaction from the headwater to the Nile Delta region. Piezometric and isotopic (δ18O, δ2H) evidence reveal that the Nile changes from a gaining stream in the headwater regions to mostly a loosing stream in the arid lowlands of Sudan and Egypt. Specific zones of Nile water leakage to the adjacent aquifers is mapped using the two sources of evidence. Up to 50% of the surface-water flow in the equatorial region of the Nile comes from groundwater as base flow. The evidence also shows that the natural direction and rate of surface-water/groundwater interaction is largely perturbed by human activities (diversion, dam construction) particularly downstream of the Aswan High Dam in Egypt. The decrease in discharge of the Nile River along its course is attributed to leakage to the aquifers as well as to evaporative water loss from the river channel. The surface-water/groundwater interaction occurring along the Nile River and its sensitivity to infrastructure development calls for management strategies that account groundwater as an integral part of the Nile Basin resources.

Structural and Sequence Stratigraphic Analysis of the Onshore Nile Delta, Egypt.

NASA Astrophysics Data System (ADS)

Barakat, Moataz; Dominik, Wilhelm

2010-05-01

The Nile Delta is considered the earliest known delta in the world. It was already described by Herodotus in the 5th Century AC. Nowadays; the Nile Delta is an emerging giant gas province in the Middle East with proven gas reserves which have more than doubled in size in the last years. The Nile Delta basin contains a thick sedimentary sequence inferred to extend from Jurassic to recent time. Structural styles and depositional environments varied during this period. Facies architecture and sequence stratigraphy of the Nile Delta are resolved using seismic stratigraphy based on (2D seismic lines) including synthetic seismograms and tying in well log data. Synthetic seismograms were constructed using sonic and density logs. The combination of structural interpretation and sequence stratigraphy of the development of the basin was resolved. Seven chrono-stratigraphic boundaries have been identified and correlated on seismic and well log data. Several unconformity boundaries also identified on seismic lines range from angular to disconformity type. Furthermore, time structure maps, velocity maps, depth structure maps as well as Isopach maps were constructed using seismic lines and log data. Several structural features were identified: normal faults, growth faults, listric faults, secondary antithetic faults and large rotated fault blocks of manly Miocene age. In some cases minor rollover structures could be identified. Sedimentary features such as paleo-channels were distinctively recognized. Typical Sequence stratigraphic features such as incised valley, clinoforms, topsets, offlaps and onlaps are identified and traced on the seismic lines allowing a good insight into sequence stratigraphic history of the Nile Delta most especially in the Miocene to Pliocene clastic sedimentary succession.

Egypt Nile delta gas plays take off

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petzet, G.A.

1996-08-26

This paper reviews the exploration and resource potential of Egypt`s Nile delta as a major gas/condensate province. It discusses the various company`s involved in developing these resources and their plans for exploitation. It reviews the drilling in the area and gives a summary of the reservoir geology of the areas. It identifies the major discoveries as they relate to the various reservoirs in the delta area.

The Nile

NASA Technical Reports Server (NTRS)

2001-01-01

This image of the northern portion of the Nile River was captured by MISR's nadir camera on January 30, 2001 (Terra orbit 5956). The Nile is the longest river in the world, extending for about 6700 kilometers from its headwaters in the highlands of eastern Africa.

At the apex of the fertile Nile River Delta is the Egyptian capital city of Cairo. To the west are the Great Pyramids of Giza. North of here the Nile branches into two distributaries, the Rosetta to the west and the Damietta to the east.

Also visible in this image is the Suez Canal, a shipping waterway connecting Port Said on the Mediterranean Sea with the Gulf of Suez. The Gulf is an arm of the Red Sea, and is located on the righthand side of the picture.

MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

A new model of river dynamics, hydroclimatic change and human settlement in the Nile Valley derived from meta-analysis of the Holocene fluvial archive

NASA Astrophysics Data System (ADS)

Macklin, Mark G.; Toonen, Willem H. J.; Woodward, Jamie C.; Williams, Martin A. J.; Flaux, Clément; Marriner, Nick; Nicoll, Kathleen; Verstraeten, Gert; Spencer, Neal; Welsby, Derek

2015-12-01

In the Nile catchment, a growing number of site- and reach-based studies employ radiocarbon and, more recently, OSL dating to reconstruct Holocene river histories, but there has been no attempt to critically evaluate and synthesise these data at the catchment scale. We present the first meta-analysis of published and publically available radiocarbon and OSL dated Holocene fluvial units in the Nile catchment, including the delta region, and relate this to changing climate and river dynamics. Dated fluvial units are separated both geographically (into the Nile Delta and White, Blue, and Desert Nile sub-regions) and into depositional environment (floodplain and palaeochannel fills). Cumulative probability density frequency (CPDF) plots of floodplain and palaeochannel units show a striking inverse relationship during the Holocene, reflecting abrupt (<100 years) climate-related changes in flooding regime. The CPDF plot of dated floodplain units is interpreted as a record of over-bank river flows, whilst the CPDF plot of palaeochannel units reflect periods of major flooding associated with channel abandonment and contraction, as well as transitions to multi-centennial length episodes of greater aridity and low river flow. This analysis has identified major changes in river flow and dynamics in the Nile catchment with phases of channel and floodplain contraction at c. 6150-5750, 4400-4150, 3700-3450, 2700-2250, 1350-900, 800-550 cal. BC and cal. AD 1600, timeframes that mark shifts to new hydrological and geomorphological regimes. We discuss the impacts of these changing hydromorphological regimes upon riverine civilizations in the Nile Valley.

Polychlorinated Biphenyls Water Pollution along the River Nile, Egypt

PubMed Central

Megahed, Ayman Mohamed; Dahshan, Hesham; Abd-El-Kader, Mahdy A.; Abd-Elall, Amr Mohamed Mohamed; Elbana, Mariam Hassan; Nabawy, Ehab; Mahmoud, Hend A.

2015-01-01

Ten polychlorinated biphenyl (PCB) congeners were determined in water samples collected along the River Nile using gas chromatography-electron capture detector (GC-ECD). PCB concentrations ranged from 14 to 20 μg/L, which were higher than those reported in previous studies, indicating serious PCB pollution in the River Nile. PCB congener profiles varied depending on the sampling sties. PCB-138 was the predominant congener accounting for more than 18% of total PCBs. The composition of PCB congeners in the water revealed that highly chlorinated PCB technical mixtures such as Aroclor 1254 was the main PCB production historically used in Egypt. An increasing trend in PCB levels from the upper stream to the Nile estuaries was observed. The calculated flux of PCBs indicated that 6.8 tons of PCBs is dumped into the Mediterranean Sea each year from the River Nile. The hazard quotients and carcinogenic risk caused by PCB pollution in the River Nile were above the acceptable level indicating that PCBs in the River Nile water pose adverse health effects for all age groups. Our findings revealed that PCBs possess a serious risk to the Egyptian population that depends mainly on the River Nile as a source of water. Thus, stricter legislation and regulatory controls should be applied to reduce the risk of PCBs in Egypt. PMID:26798844

Using Persistent Scatterers Interferometry to create a subsidence map of the Nile Delta in Egypt

NASA Astrophysics Data System (ADS)

Bouali, E. Y.; Sultan, M.; Becker, R.; Cherif, O.

2013-12-01

subsidence rates vary widely across the Nile Delta, with the highest rates occurring in cities near the mouth of the Damietta branch of the Nile River and around the Mansala Lagoon, such as Ras El Bar (up to 15 mm/year), Damietta (up to 10 mm/year), and Port Said (up to 7 mm/year). The complexity of these subsidence rates is spatially evident: many cities display a wide range of subsidence rates - for example Port Said, where a majority of the city is undergoing minimal to no subsidence (< 1 mm/year) there are two regions - near the Mediterranean coast and near the Mansala Lagoon - where subsidence rates are quite high (5-7 mm/year). There are also a few overall trends observed across the delta: (1) subsidence rates are greatest in the northeast region of the delta (average: > 5 mm/year) than anywhere else (e.g., average western subsidence: 1-4 mm/year) and (2) cities generally more proximal to the Mediterranean coast exhibit greater subsidence rates (average subsidence rates: Ras El Bar: 8 mm/year, Port Said: 5 mm/year, and Damietta: 6 mm/year)than cities in the middle (e.g., Mansoura and Al Mahallah: 4 mm/year) or south regions (e.g., Tanta: <4 mm/year) of the delta.

On the origins of hypersaline groundwater in the Nile Delta aquifer

NASA Astrophysics Data System (ADS)

van Engelen, Joeri; Oude Essink, Gualbert H. P.; Kooi, Henk; Bierkens, Marc F. P.

2018-05-01

The Nile Delta is essential to Egypt's agro- and socio-economy. Although surface water is the traditional source for Egypt's irrigation, the shallow fresh groundwater resources underlying the delta are increasingly burdened by groundwater pumping, which increases interest in the status of the groundwater resources. Groundwater up to three times more saline than sea water was found at 600 m depth. The occurrence of this hypersaline groundwater raises doubts on the often-made assumption in the literature that seawater is the only source of salt in the Nile Delta aquifer and makes further investigation necessary. Knowledge on the origin of this hypersaline groundwater is key in assessing the possibility of deep fresh groundwater pockets. In this paper we conducted computational analyses to assess possible origins using both analytical solutions and numerical models. It is concluded that the hypersaline groundwater can either originate from Quaternary free convection systems, or from compaction-induced upward salt transport of hypersaline groundwater that formed during the Messinian salinity crisis. Our results also indicate that with groundwater dating it is possible to discriminate between these two hypotheses. Furthermore, it is deduced that the hydrological connection between aquifer and sea is crucial to the hydrogeological functioning of the Nile Delta Aquifer.

On the origins of hypersaline groundwater in the Nile Delta Aquifer

NASA Astrophysics Data System (ADS)

van Engelen, Joeri; Oude Essink, Gualbert H. P.; Kooi, Henk; Bierkens, Marc F. P.

2017-04-01

The fresh groundwater resources in the Nile Delta, Egypt, are of eminent socio-economic importance. These resources are under major stress due to population growth, the anticipated sea level rise and increased groundwater extraction rates, making fresh water availability the most challenging issue in this area. Up till now, numerous groundwater studies mainly focused on sea water intrusion on the top 100m of the groundwater system and assumed salinities not exceeding that of Mediterranean sea water, as there was no knowledge on groundwater in the deeper coastal parts of the Quaternary Nile Delta aquifer (that ranges up to 1000m depth). Recently, however, the Egyptian Research Institute for Groundwater (RIGW) collected salinity measurements and found a widespread occurrence of "hypersaline" groundwater: groundwater with salinities largely exceeding that of sea water at 600m depth (Nofal et al., 2015). This hypersaline groundwater greatly influences flow patterns and the fresh water potential of the aquifer. This research focuses on the origins of the hypersaline groundwater and the possible processes causing its transport. We consider all relevant salinization processes in the Nile Delta aquifer, over a time domain of up to 2.5 million years, which is the time span in which the aquifer got deposited. The following hypotheses were investigated with a combination of analytical solutions and numerical modelling: upward salt transport due to a) molecular diffusion, b) thermal buoyancy, c) consolidation-induced advection and dispersion, or downward transport due to d) composition buoyancy (salt inversion). We conclude that hypotheses a) and b) can be rejected, but c) and d) are both possible with the available information. An enhanced chemical analysis is suggested for further research, to determine the origins of this hypersaline water. This information in combination with the conclusions drawn in this research will give more insight in the potential amount of non

Vulnerability of the Nile Delta coastal areas to inundation by sea level rise.

PubMed

Hassaan, M A; Abdrabo, M A

2013-08-01

Sea level changes are typically caused by several natural phenomena, including ocean thermal expansion, glacial melt from Greenland and Antarctica. Global average sea level is expected to rise, through the twenty-first century, according to the IPCC projections by between 0.18 and 0.59 cm. Such a rise in sea level will significantly impact coastal area of the Nile Delta, consisting generally of lowland and is densely populated areas and accommodates significant proportion of Egypt's economic activities and built-up areas. The Nile Delta has been examined in several previous studies, which worked under various hypothetical sea level rise (SLR) scenarios and provided different estimates of areas susceptible to inundation due to SLR. The paper intends, in this respect, to identify areas, as well as land use/land cover, susceptible to inundation by SLR based upon most recent scenarios of SLR, by the year 2100 using GIS. The results indicate that about 22.49, 42.18, and 49.22 % of the total area of coastal governorates of the Nile Delta would be susceptible to inundation under different scenarios of SLR. Also, it was found that 15.56 % of the total areas of the Nile Delta that would be vulnerable to inundation due to land subsidence only, even in the absence of any rise in sea level. Moreover, it was found that a considerable proportion of these areas (ranging between 32.32 and 53.66 %) are currently either wetland or undeveloped areas. Furthermore, natural and/or man-made structures, such as the banks of the International Coastal Highway, were found to provide unintended protection to some of these areas. This suggests that the inundation impact of SLR on the Nile Delta is less than previously reported.

Ocean-color remote sensing of the Nile delta shelf and SE Levantine basin and possible linkage to some mesoscale circulation features and Nile river run-off

NASA Astrophysics Data System (ADS)

Moufaddal, Wahid; Lavender, Samantha

To date, and despite the passage of more than 30 years since the launch of the first satellite based ocean-color sensor, no systematic study of the variability of chlorophyll in the Egyptian Mediterranean coast off the Nile delta has been undertaken using this kind of data. Meantime, available in-situ measurements on chlorophyll and other nutrient parameters along this coast are indeed very modest and scarce. The lack of data has in turn created a large gap in our knowledge on the biogeochemical characteristics of the coastal water and impacts of the Aswan High Dam and other land-use changes on the marine ecosystems and nutrient budget in the Nile delta shelf and the SE Mediterranean. The present study aims to fill part of this gap through application of ocean-color remote sensing and satellite retrieval of phytoplankton chlorophyll. For this purpose a 10-year (1997-2006) monthly satellite dataset from ESA Globcolour project (an ESA Data User Element project: http://www.globcolour.info) was retrieved and subjected to time-series analysis. Results of this analysis revealed that the oceanic and coastal parts off the Nile delta coast and SE Mediterranean manifest from time to time some of the most interesting and dynamical marine features including meso-scale gyres, coastal filaments, localized algal blooms and higher concentration of phytoplankton chlorophyll. These features together with certain physical pro-cesses and surface run-off from Nile mouthes and other land-based sources were found to exert pronounced effects on the nutrient supply and quality of the coastal and oceanic surface waters in this region. Results reveled also that there has been a general upward trend in concentration of surface chlorophyll during the 10-year period from 1997 to 2006 with a coincident rise of the coastal fisheries implying that improvement of nutrient supply is most likely responsible for this rise. Results confirmed also shift of the Nile phytoplankton bloom in space and time

Natural equilibria and anthropic effects on sediment transport in big river systems: The Nile case

NASA Astrophysics Data System (ADS)

Garzanti, Eduardo; Andò, Sergio; Padoan, Marta; Vezzoli, Giovanni; Villa, Igor

2014-05-01

The Nile River flows for ~ 6700 km, from Burundi and Rwanda highlands south of the Equator to the Mediterranean Sea at northern subtropical latitudes. It is thus the longest natural laboratory on Earth, a unique setting in which we are carrying out a continuing research project to investigate changes in sediment composition associated with a variety of chemical and physical processes, including weathering in equatorial climate and hydraulic sorting during transport and deposition. Petrographic, mineralogical, chemical, and isotopic fingerprints of sand and mud have been monitored along all Nile branches, from the Kagera and White Nile draining Archean, Paleoproterozoic and Mesoproterozoic basements uplifted along the western branch of the East African rift, to the Blue Nile and Atbara Rivers sourced in Ethiopian volcanic highlands made of Oligocene basalt. Downstream of the Atbara confluence, the Nile receives no significant tributary water and hardly any rainfall across the Sahara. After construction of the Aswan High Dam in 1964, the Nile ceased to be an active conveyor-belt in Egypt, where the mighty river has been tamed to a water canal; transported sediments are thus chiefly reworked from older bed and levee deposits, with minor contributions from widyan sourced in the Red Sea Hills and wind-blown desert sand and dust. Extensive dam construction has determined a dramatic sediment deficit at the mouth, where deltaic cusps are undergoing ravaging erosion. Nile delta sediments are thus recycled under the effect of dominant waves from the northwest, the longest Mediterranean fetch direction. Nile sands, progressively enriched in more stable minerals such as quartz and amphiboles relative to volcanic rock fragments and pyroxene, thus undergo multistep transport by E- and NE-directed longshore currents all along the coast of Egypt and Palestine, and are carried as far as Akko Bay in northern Israel. Nile mud reaches the Iskenderun Gulf in southern Turkey. A full

STS-57 Earth observation of the Eastern Mediterranean, Nile River, Asia Minor

NASA Technical Reports Server (NTRS)

1993-01-01

STS-57 Earth observation of the Eastern Mediterranean. From a high vantage point over the Nile River, this north-looking view shows the eastern Mediterranean and the entire landmass of Asia Minor, with the Black Sea dimly visible at the horizon. Many of the Greek islands can be seen in the Aegean Sea (top left), off the coast of Asia Minor. Cyprus is visible under atmospheric dust in the northeastern corner of the Mediterranean. The dust cloud covers the east end of the Mediterranean, its western edge demarcated by a line that cuts the center of the Nile Delta. This dust cloud originated far to the west, in Algeria, and moved northeast. A gyre of clouds in the southeast corner of the Mediterranean indicates a complementary counterclockwise (cyclonic) circulation of air. The Euphrates River appears as a thin green line (upper right) in the yellow Syrian desert just south of the mountains of Turkey. The Dead Sea (lower right) lies in a rift valley which extends north into Turkey and sout

Nile Delta

NASA Image and Video Library

2013-06-19

Urbanized areas of northern Egypt are visible amidst the deserts of Egypt. The image captured July 9-15, 2012 also shows the Nile River which provides life-sustaining water to the region. The image was created from the Visible-Infrared Imager/Radiometer Suite (VIIRS) instrument aboard the Suomi National Polar-orbiting Partnership or Suomi NPP satellite, a partnership between NASA and the National Oceanic and Atmospheric Administration, or NOAA. Credit: NASA/NOAA To read more go to: www.nasa.gov/mission_pages/NPP/news/vegetation.html NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Nile River Fluctuations Near Khartoum, Sudan

NASA Image and Video Library

2001-08-29

Throughout history, the rising and falling waters of the mighty Nile River have directly impacted the lives of the people who live along its banks. These images of the area around Sudan's capital city of Khartoum capture the river's dynamic nature. Acquired by the Multi-angle Imaging SpectroRadiometer's nadir (vertical-viewing) camera, they display the extent of the Nile waters before and after the onset of the rainy seasons of 2000 (top pair) and 2001 (bottom pair). The images are displayed in "false color," using the camera's near-infrared, green, and blue bands. With this particular spectral combination, water appears in shades of blue and turquoise, and highly vegetated areas show up as bright red. Originating in Uganda and Ethiopia, respectively, the waters of the White Nile (western branch) and Blue Nile (eastern branch) converge at Khartoum (about half-way between image center and the left-hand side), and continue to flow northward as the Great Nile. Although the most obvious feature in these images is the increased width of the White Nile between spring and summer, careful inspection shows that the Great Nile is at its widest in August 2001 (note in particular the area between the clouds near the top of this panel). Heavy rains in the Blue Nile catchment area of the Ethiopian highlands led to a rapid overflow of the river's floodwaters into the main stream of the Great Nile, leading to extensive flooding, the worst effects of which occurred north of Khartoum. According to the Food and Agriculture Organization of the United Nations, tens of thousands of people have fled their homes, and the number of people in need of urgent food assistance in Sudan, estimated at three million earlier in the year, was likely to increase with the onset of these floods. South of the confluence of the White Nile and the Blue Nile, the area of a cross-hatched appearance is the irrigated plain of El Gezira. The Gezira irrigation scheme uses water from the Makwar Dam (now called

Metal pollution loading, Manzalah lagoon, Nile delta, Egypt: Implications for aquaculture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siegel, F.R.; Slaboda, M.L.; Stanley, D.J.

1994-03-01

High cultural enrichment factors are found for Hg (13 x), Pb (22.1 x), and other potentially toxic metals (e.g., Sn, Zn, Cu, Ag) in the upper 20 cm of sediment cores from the southeastern Ginka subbasin of Manzalah lagoon, Nile delta, Egypt. Cores from other areas of the lagoon show little metal loading. Metal loading followed the closure of the Aswan High Dam, the availability of abundant cheap electricity, and the development of major power-based industries. Industrial wastes containing potentially toxic metals are dumped into the Nile delta drain system. The load carried by Bahr El-Baqar drain discharges into themore » Ginka subbasin, which acts as a sink and results in metal loading of the sediment deposited there. Further development of aquaculture in this subbasin, of food-stuff agriculture on recently reclaimed lagoon bottom, or where irrigation waters come from Bahr El-Baqar drain or its discharge should be halted or strictly limited until potentially toxic metals in the drain waters and sediment are removed and polluted input drastically reduced. This environmental assessment of heavy metals in aquaculture or agriculture development should extend to other waterbodies in the northern Nile delta, particularly Idku lagoon and Lake Mariut, where industrial metal-bearing wastes discharge into the waterbodies. 21 refs., 7 figs., 3 tabs.« less

Discover the Nile River

ERIC Educational Resources Information Center

Project WET Foundation, 2009

2009-01-01

Bordering on the Fantastic. As the longest river on earth, the Nile passes through 10 countries. Presented through a wide range of activities and a winning array of games, it's also unsurpassed at taking young minds into exploring the world of water, as well as natural and man made wonders.

Holocene evolution of the northeastern corner of the Nile Delta

NASA Astrophysics Data System (ADS)

Sneh, A.; Weissbrod, T.; Ehrlich, A.; Horowitz, A.; Moshkovitz, S.; Rosenfeld, A.

1986-09-01

The constructive phase of the modern Nile Delta, as manifested in a 48-m section drilled east of the Suez Canal, commenced in very early Holocene times. Sands rich in marine fauna were deposited in the littoral zone and the shoreline was more than 20 km landward of its present-day position. Subsequently, clays and silts were dumped from the Nile distributaries and the marine faunal spectrum became very limited and brackish. Later in early and middle Holocene times the sediments deposited were rich in freshwater, delta-plain diatoms and pollen and in allochthonous fern spores from the tropics, indicating proximity of a distributary mouth. The middle part of the section (22.5-17.5 m) is very poor in faunal and floral remains; pollen grains from sabkha vegetation are abundant. The environment, which seems lagoonal and slightly hypersaline, is related to the sea regression in middle Holocene times. Euryhaline pelecypods, dating from about 3000 yr B.P., are abundant around the 8-m depth. Upward, there is an increase in pollen grains from sabkhas; the section is poor in diatoms and those present are mostly euryhaline and lagoonal. Allochthonous spores derived from the nearby Pelusiac Branch are abundant. Between 3000 and 2000 yr B.P. the constructive phase of the modern delta terminated and winnowed sands began accreting in front of the delta plain.

Climate change enhances interannual variability of the Nile river flow

NASA Astrophysics Data System (ADS)

Siam, Mohamed S.; Eltahir, Elfatih A. B.

2017-04-01

The human population living in the Nile basin countries is projected to double by 2050, approaching one billion. The increase in water demand associated with this burgeoning population will put significant stress on the available water resources. Potential changes in the flow of the Nile River as a result of climate change may further strain this critical situation. Here, we present empirical evidence from observations and consistent projections from climate model simulations suggesting that the standard deviation describing interannual variability of total Nile flow could increase by 50% (+/-35%) (multi-model ensemble mean +/- 1 standard deviation) in the twenty-first century compared to the twentieth century. We attribute the relatively large change in interannual variability of the Nile flow to projected increases in future occurrences of El Niño and La Niña events and to observed teleconnection between the El Niño-Southern Oscillation and Nile River flow. Adequacy of current water storage capacity and plans for additional storage capacity in the basin will need to be re-evaluated given the projected enhancement of interannual variability in the future flow of the Nile river.

Satellite mapping of Nile Delta coastal changes

NASA Technical Reports Server (NTRS)

Blodget, H. W.; Taylor, P. T.; Roark, J. H.

1989-01-01

Multitemporal, multispectral scanner (MSS) landsat data have been used to monitor erosion and sedimentation along the Rosetta Promontory of the Nile Delta. These processes have accelerated significantly since the completion of the Aswan High Dam in 1964. Digital differencing of four MSS data sets, using standard algorithms, show that changes observed over a single year period generally occur as strings of single mixed pixels along the coast. Therefore, these can only be used qualitatively to indicate areas where changes occur. Areas of change recorded over a multi-year period are generally larger and thus identified by clusters of pixels; this reduces errors introduced by mixed pixels. Satellites provide a synoptic perspective utilizing data acquired at frequent time intervals. This permits multiple year monitoring of delta evolution on a regional scale.

Cairo, Egypt/Nile River viewed from STS-66 Atlantis

NASA Image and Video Library

1994-11-14

This close-up view of the intensively cultivated Nile River flood plain near Cairo presents a sharp color contrast to the virtually non-vegetated, sandy desert, located to the west of the vegetated area. Some rectangular cultivated field patterns, as well as circular center pivot irrigation patterns, can be observed northwest of the Nile River flood plain. The world famous Giza Pyramids are located near the center of this photography (see highly reflective sand surfaces).

Zambezi River Delta

NASA Image and Video Library

2013-08-29

It drains a watershed that spans eight countries and nearly 1.6 million square kilometers 600,000 square miles. The Zambezi also Zambeze is the fourth largest river in Africa, and the largest east-flowing waterway. The Operational Land Imager on the Landsat 8 satellite acquired this natural-color image of the Zambezi Delta on August 29, 2013. Sandbars and barrier spits stretch across the mouths of the delta, and suspended sediment extends tens of kilometers out into the sea. The sandy outflow turns the coastal waters to a milky blue-green compared to the deep blue of open water in the Indian Ocean. The Zambezi Delta includes 230 kilometers of coastline fronting 18,000 square kilometers (7,00 square miles) of swamps, floodplains, and even savannahs (inland). The area has long been prized by subsistence fishermen and farmers, who find fertile ground for crops like sugar and fertile waters for prawns and fish. Two species of endangered cranes and one of the largest concentration of buffalo in Africa -- among many other species of wildlife -- have found a haven in this internationally recognized wetland. However, the past six decades have brought great changes to the Zambezi Delta, which used to pour more water and sediment off of the continent. Hydropower dams upstream-most prominently, the Kariba and the Cahora Bassa-greatly reduce river flows during the wet season; they also trap sediments that would otherwise flow downstream. The result has been less water reaching the delta and the floodplains, which rely on pulses of nutrients and sediments from annual (and mostly benign) natural flooding. The change in the flow of the river affects freshwater availability and quality in the delta. Strong flows push fresh water further out into the sea and naturally keep most of a delta full of fresh (or mostly fresh) water. When that fresh flow eases, the wetlands become drier and more prone to fire. Salt water from the Indian Ocean also can penetrate further into the marsh

Explaining and forecasting interannual variability in the flow of the Nile River

NASA Astrophysics Data System (ADS)

Siam, M. S.; Eltahir, E. A. B.

2014-05-01

The natural interannual variability in the flow of Nile River had a significant impact on the ancient civilizations and cultures that flourished on the banks of the river. This is evident from stories in the Bible and Koran, and from the numerous Nilometers discovered near ancient temples. Here, we analyze extensive data sets collected during the 20th century and define four modes of natural variability in the flow of Nile River, identifying a new significant potential for improving predictability of floods and droughts. Previous studies have identified a significant teleconnection between the Nile flow and the Eastern Pacific Ocean. El Niño-Southern Oscillation (ENSO) explains about 25% of the interannual variability in the Nile flow. Here, we identify, for the first time, a region in the southern Indian Ocean with similarly strong teleconnection to the Nile flow. Sea Surface Temperature (SST) in the region (50-80° E and 25-35° S) explains 28% of the interannual variability in the Nile flow. During those years with anomalous SST conditions in both Oceans, we estimate that indices of the SSTs in the Pacific and Indian Oceans can collectively explain up to 84% of the interannual variability in the flow of Nile. Building on these findings, we use classical Bayesian theorem to develop a new hybrid forecasting algorithm that predicts the Nile flow based on global models predictions of indices of the SST in the Eastern Pacific and Southern Indian Oceans.

Major and trace element distribution in soil and sediments from the Egyptian central Nile Valley

NASA Astrophysics Data System (ADS)

Badawy, W. M.; Ghanim, E. H.; Duliu, O. G.; El Samman, H.; Frontasyeva, M. V.

2017-07-01

The distributions of 32 major and trace elements in 72 surface soil and sediment samples collected from the Asyut to Cairo Nile river section were determined by epithermal neutron activation analysis and compared with corresponding data for the Upper Continental Crust, North American Shale Composite, Average Soil and Average Sediment as well as suspended sediments from Congo and Upper Niger Rivers, in order to establish to which extent the Nile sedimentary material can be related to similar material all over the world as well as to local geology. Their relative distributions indicate the presence of detrital material of igneous origin, most probably resulting from weathering of the Ethiopian Highlands and transported by the Blue Nile, the Nile main tributary. The distributions of nickel, zinc, and arsenic contents suggest that the lower part of the Nile and its surroundings including the Nile Delta is not seriously polluted with heavy metals, so that, in spite of a human activity, which lasted four millennia, the Nile River continues to be less affected by any anthropogenic contamination.

Dynamics of wind setdown at Suez and the Eastern Nile Delta.

PubMed

Drews, Carl; Han, Weiqing

2010-08-30

Wind setdown is the drop in water level caused by wind stress acting on the surface of a body of water for an extended period of time. As the wind blows, water recedes from the upwind shore and exposes terrain that was formerly underwater. Previous researchers have suggested wind setdown as a possible hydrodynamic explanation for Moses crossing the Red Sea, as described in Exodus 14. This study analyzes the hydrodynamic mechanism proposed by earlier studies, focusing on the time needed to reach a steady-state solution. In addition, the authors investigate a site in the eastern Nile delta, where the ancient Pelusiac branch of the Nile once flowed into a coastal lagoon then known as the Lake of Tanis. We conduct a satellite and modeling survey to analyze this location, using geological evidence of the ancient bathymetry and a historical description of a strong wind event in 1882. A suite of model experiments are performed to demonstrate a new hydrodynamic mechanism that can cause an angular body of water to divide under wind stress, and to test the behavior of our study location and reconstructed topography. Under a uniform 28 m/s easterly wind forcing in the reconstructed model basin, the ocean model produces an area of exposed mud flats where the river mouth opens into the lake. This land bridge is 3-4 km long and 5 km wide, and it remains open for 4 hours. Model results indicate that navigation in shallow-water harbors can be significantly curtailed by wind setdown when strong winds blow offshore.

Water quality assessment of the River Nile system: an overview.

PubMed

Wahaab, Rifaat A; Badawy, Mohamed I

2004-03-01

The main objective of the present article is to assess and evaluate the characteristics of the Nile water system, and identify the major sources of pollution and its environmental and health consequences. The article is also aimed to highlight the importance of water management via re-use and recycle of treated effluents for industrial purpose and for cultivation of desert land. An intensive effort was made by the authors to collect, assess and compile the available data about the River Nile. Physico-chemical analyses were conducted to check the validity of the collected data. For the determination of micro-pollutants, Gas Chromatography (GC) and High Performance Liquid Chromatography (HPLC) were used. Heavy metals were also determined to investigate the level of industrial pollution in the river system. The available data revealed that the river receives a large quantity of industrial, agriculture and domestic wastewater. It is worth mentioning that the river is still able to recover in virtually all the locations, with very little exception. This is due to the high dilution ratio. The collected data confirmed the presence of high concentrations of chromium and manganese in all sediment samples. The residues of organo-chlorine insecticides were detected in virtually all locations. However, the levels of such residues are usually below the limit set by the WHO for use as drinking water. The most polluted lakes are Lake Maryut and Lake Manzala. Groundwater pollution is closely related to adjacent (polluted) surface waters. High concentrations of nutrients, E. coli, sulfur, heavy metals, etc. have been observed in the shallow groundwater, largely surpassing WHO standards for drinking water use. A regular and continuous monitoring scheme shall be developed for the River Nile system. The environmental law shall be enforced to prohibit the discharge of wastewater (agricultural, domestic or industrial) to River Nile system.

Decadal biogeochemical history of the south east Levantine basin: Simulations of the river Nile regimes

NASA Astrophysics Data System (ADS)

Suari, Yair; Brenner, Steve

2015-08-01

The south eastern Mediterranean is characterized by antiestuarine circulation which leads to extreme oligotrophic conditions. The Nile river that used to transport fresh water and nutrients into the basin was dammed in 1964 which led to a drastic reduction of fresh water fluxes, and later, changes in Egyptian agriculture and diet led to increased nutrient fluxes. In this paper we present the results of simulations with a biogeochemical model of the south eastern Mediterranean. Four experiments were conducted: (1) present day without riverine inputs; (2) Nile before damming (pre-1964); (3) post-damming 1995 Nile; and (4) fresh water and nutrient discharges of Israeli coastal streams. The present day input simulation (control run) successfully reproduced measured nutrient concentrations, with the exception of simulated chlorophyll concentrations which were slightly higher than observed. The pre-1964 Nile simulation showed a salinity reduction of 2 psu near the Egyptian coast and 0.5 psu along the Israeli coast, as well as elevated chlorophyll a concentrations mostly east of the Nile delta and north to Cyprus. The spring bloom extended from its present peak during February-March to a peak during February-May. The 1995 Nile simulation showed increased chlorophyll a concentrations close to the Egyptian coast. The Israeli coastal stream simulation showed that the effect of the Israeli coastal stream winter flow on chlorophyll converged to control concentrations within about one month, demonstrating the stability and sensitivity of the model to external forcing. The results of this study demonstrate the significance of fresh water fluxes in maintaining marine productivity, which may have large scale effects on the marine ecosystem.

Tidal controls on river delta morphology

NASA Astrophysics Data System (ADS)

Hoitink, A. J. F.; Wang, Z. B.; Vermeulen, B.; Huismans, Y.; Kästner, K.

2017-09-01

River delta degradation has been caused by extraction of natural resources, sediment retention by reservoirs, and sea-level rise. Despite global concerns about these issues, human activity in the world’s largest deltas intensifies. Harbour development, construction of flood defences, sand mining and land reclamation emerge as key contemporary factors that exert an impact on delta morphology. Tides interacting with river discharge can play a crucial role in the morphodynamic development of deltas under pressure. Emerging insights into tidal controls on river delta morphology suggest that--despite the active morphodynamics in tidal channels and mouth bar regions--tidal motion acts to stabilize delta morphology at the landscape scale under the condition that sediment import during low flows largely balances sediment export during high flows. Distributary channels subject to tides show lower migration rates and are less easily flooded by the river because of opposing non-linear interactions between river discharge and the tide. These interactions lead to flow changes within channels, and a more uniform distribution of discharge across channels. Sediment depletion and rigorous human interventions in deltas, including storm surge defence works, disrupt the dynamic morphological equilibrium and can lead to erosion and severe scour at the channel bed, even decades after an intervention.

Nile Delta

Atmospheric Science Data Center

2013-04-15

... west are the Great Pyramids of Giza. North of here the Nile branches into two distributaries, the Rosetta to the west and the Damietta to ... NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Science Mission Directorate, Washington, D.C. The Terra spacecraft is managed ...

Dynamics of Wind Setdown at Suez and the Eastern Nile Delta

PubMed Central

Drews, Carl; Han, Weiqing

2010-01-01

Background Wind setdown is the drop in water level caused by wind stress acting on the surface of a body of water for an extended period of time. As the wind blows, water recedes from the upwind shore and exposes terrain that was formerly underwater. Previous researchers have suggested wind setdown as a possible hydrodynamic explanation for Moses crossing the Red Sea, as described in Exodus 14. Methodology/Principal Findings This study analyzes the hydrodynamic mechanism proposed by earlier studies, focusing on the time needed to reach a steady-state solution. In addition, the authors investigate a site in the eastern Nile delta, where the ancient Pelusiac branch of the Nile once flowed into a coastal lagoon then known as the Lake of Tanis. We conduct a satellite and modeling survey to analyze this location, using geological evidence of the ancient bathymetry and a historical description of a strong wind event in 1882. A suite of model experiments are performed to demonstrate a new hydrodynamic mechanism that can cause an angular body of water to divide under wind stress, and to test the behavior of our study location and reconstructed topography. Conclusions/Significance Under a uniform 28 m/s easterly wind forcing in the reconstructed model basin, the ocean model produces an area of exposed mud flats where the river mouth opens into the lake. This land bridge is 3–4 km long and 5 km wide, and it remains open for 4 hours. Model results indicate that navigation in shallow-water harbors can be significantly curtailed by wind setdown when strong winds blow offshore. PMID:20827299

Normal haematology and blood biochemistry of wild Nile crocodiles (Crocodylus niloticus) in the Okavango Delta, Botswana.

PubMed

Lovely, C J; Pittman, J M; Leslie, A J

2007-09-01

Wild Nile crocodiles (Crocodylus niloticus) of various size classes were captured in the Okavango Delta, Botswana. Blood was collected from the post occipital sinus and used for the determination of a wide range of haematological and biochemical parameters. These values were compared between the sexes and between 3 size classes. The values were also compared with the limited data available from farmed Nile crocodiles, as well as from other wild Nile crocodiles. The Okavango crocodiles were comparatively anaemic, and had comparatively low total protein and blood glucose levels. There was a high prevalence of Hepatozoon pettiti infection, however, there was no significant difference in haematological values between the infected and uninfected crocodiles. The values reported here will be useful in diagnostic investigations in both zoo and farmed Nile crocodiles.

Mississippi River Delta

NASA Image and Video Library

2002-06-11

As the Mississippi River enters the Gulf of Mexico, it loses energy and dumps its load of sediment that it has carried on its journey through the mid continent. This pile of sediment, or mud, accumulates over the years building up the delta front. As one part of the delta becomes clogged with sediment, the delta front will migrate in search of new areas to grow. The area shown on this image is the currently active delta front of the Mississippi. The migratory nature of the delta forms natural traps for oil. Most of the land in the image consists of mud flats and marsh lands. There is little human settlement in this area due to the instability of the sediments. The main shipping channel of the Mississippi River is the broad stripe running northwest to southeast. This image was acquired on May 24, 2001 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet. http://photojournal.jpl.nasa.gov/catalog/PIA03497

Comparison of Prognostic and Diagnostic Approaches to Modeling Evapotranspiration in the Nile River Basin

NASA Astrophysics Data System (ADS)

Yilmaz, M.; Anderson, M. C.; Zaitchik, B. F.; Crow, W. T.; Hain, C.; Ozdogan, M.; Chun, J. A.

2012-12-01

may be a valuable model evaluation tool. Motivated by the complementary information that exists in prognostic and diagnostic energy balance modeling, as well as the need for evaluation of water consumption estimates over the Nile basin, the purpose of this study is to 1) better describe the conceptual differences between prognostic and diagnostic modeling, 2) present the potential for diagnostic models to capture important hydrologic features that are not explicitly represented in prognostic model, 3) explore the differences in these two approaches over the Nile Basin, where ground data are sparse and transnational data sharing is unreliable. More specifically, we will compare output from the Noah prognostic model and the Atmosphere-Land Exchange Inverse (ALEXI) diagnostic model generated over ground truth data-poor Nile basin. Preliminary results indicate spatially, temporally, and magnitude wise consistent flux estimates for ALEXI and NOAH over irrigated Delta region, while there are differences over river-fed wetlands.

Mosquitoes and the environment in Nile Delta villages with previous rift valley fever activity

USDA-ARS?s Scientific Manuscript database

Egypt is affected by serious human and animal mosquito-borne diseases such as Rift Valley fever (RVF). We investigated how potential RVF virus mosquito vector populations are affected by environmental conditions in the Nile Delta region of Egypt by collecting mosquitoes and environmental data from t...

Investigation of potential sea level rise impact on the Nile Delta, Egypt using digital elevation models.

PubMed

Hasan, Emad; Khan, Sadiq Ibrahim; Hong, Yang

2015-10-01

In this study, the future impact of Sea Level Rise (SLR) on the Nile Delta region in Egypt is assessed by evaluating the elevations of two freely available Digital Elevation Models (DEMs): the SRTM and the ASTER-GDEM-V2. The SLR is a significant worldwide dilemma that has been triggered by recent climatic changes. In Egypt, the Nile Delta is projected to face SLR of 1 m by the end of the 21th century. In order to provide a more accurate assessment of the future SLR impact on Nile Delta's land and population, this study corrected the DEM's elevations by using linear regression model with ground elevations from GPS survey. The information for the land cover types and future population numbers were derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) land cover and the Gridded Population of the Worlds (GPWv3) datasets respectively. The DEM's vertical accuracies were assessed using GPS measurements and the uncertainty analysis revealed that the SRTM-DEM has positive bias of 2.5 m, while the ASTER-GDEM-V2 showed a positive bias of 0.8 m. The future inundated land cover areas and the affected population were illustrated based on two SLR scenarios of 0.5 m and 1 m. The SRTM DEM data indicated that 1 m SLR will affect about 3900 km(2) of cropland, 1280 km(2) of vegetation, 205 km(2) of wetland, 146 km(2) of urban areas and cause more than 6 million people to lose their houses. The overall vulnerability assessment using ASTER-GDEM-V2 indicated that the influence of SLR will be intense and confined along the coastal areas. For instance, the data indicated that 1 m SLR will inundate about 580 Km(2) (6%) of the total land cover areas and approximately 887 thousand people will be relocated. Accordingly, the uncertainty analysis of the DEM's elevations revealed that the ASTER-GDEM-V2 dataset product was considered the best to determine the future impact of SLR on the Nile Delta region.

Growth laws for sub-delta crevasses in the Mississippi River Delta

NASA Astrophysics Data System (ADS)

Yocum, T. A.; Georgiou, I. Y.; Straub, K. M.

2017-12-01

River deltas are threatened by environmental change, including subsidence, global sea level rise, reduced sediment inputs and other local factors. In the Mississippi River Delta (MRD) these impacts are exemplified, and have led to proposed solutions to build land that include sediment diversions to reinitiate the delta cycle. Deltas were studied extensively using numerical models, theoretical and conceptual frameworks, empirical scaling relationships, laboratory models and field observations. But predicting the future of deltas relies on field observations where for most deltas data are still lacking. Moreover, empirical and theoretical scaling laws may be influenced by the data used to develop them, while laboratory deltas may be influenced by scaling issues. Anthropogenic crevasses in the MRD are large enough to overcome limitations of laboratory deltas, and small enough to allow for rapid channel and wetland development, providing an ideal setting to investigate delta development mechanics. Here we assessed growth laws of sub-delta crevasses (SDC) in the MRD, in two experimental laboratory deltas (LD - weakly and strongly cohesive) and compared them to river dominated deltas worldwide. Channel and delta geometry metrics for each system were obtained using geospatial tools, bathymetric datasets, sediment size, and hydrodynamic observations. Results show that SDC follow growth laws similar to large river dominated deltas, with the exception of some that exhibit anomalous behavior with respect to the frequency and distance to a bifurcation and the fraction of wetted delta shoreline (allometry metrics). Most SDC exhibit a systematic decrease of non-dimensional channel geometries with increased bifurcation order, indicating that channels are adjusting to decreased flow after bifurcations occur, and exhibit linear trends for land allometry and width-depth ratio, although geometries decrease more rapidly per bifurcation order. Measured distance to bifurcations in SDC

Assessment of Undiscovered Oil and Gas Resources of the Nile Delta Basin Province, Eastern Mediterranean

USGS Publications Warehouse

Kirschbaum, Mark A.; Schenk, Christopher J.; Charpentier, Ronald R.; Klett, Timothy R.; Brownfield, Michael E.; Pitman, Janet K.; Cook, Troy A.; Tennyson, Marilyn E.

2010-01-01

The U.S. Geological Survey estimated means of 1.8 billion barrels of recoverable oil, 223 trillion cubic feet of recoverable gas, and 6 billion barrels of natural gas liquids in the Nile Delta Basin Province using a geology-based assessment methodology.

Maturation history of Neogene-Quaternary sediments, Nile delta basin, Egypt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramadan Abu El-Ella

1990-01-01

The present Nile delta area covers approximately 60,000 km{sup 2}. Fields in this area provide two-thirds of the gas production in Egypt. Geological knowledge of the Nile delta is still limited because of insufficient subsurface data. Gas is generated and accumulates at stratigraphic levels ranging from the lower Miocene to the lower Pliocene. The highest levels of organic maturation in the Neogene-Quaternary section are in the northern part of the onshore area, such as in the Abu Madi well, and in the eastern part of the offshore area, such as in the El Temsah well, where gas reservoirs occur inmore » the lower Pliocene sandstones (Abu Madi Formation), and in the underlying Sidi Salem Formation and lower Miocene rocks. Here, the Sidi Salem Formation is probably generative, having an R{sub 0} of approximately 0.65%, LOM (levels of organic metamorphism) of 9.5 to 9.7, and TTI (time-temperature index) of 9.7 to 15.2. By contrast, a different thermal history clearly existed in the western and eastern parts of the onshore area, such as in the Monaga and Damanhur wells, where the organic maturities are significantly lower than maturities elsewhere in the basin (R{sub 0} = 0.38 and 0.29%, respectively). The predicted maturities obtained by using the LOM method seem to fit much closer to the observed maturities than the predicted maturities obtained by using the Lopatin TTI method. 5 figs.« less

Changes in the areal extents of the Athabasca River, Birch River, and Cree Creek Deltas, 1950-2014, Peace-Athabasca Delta, Canada

NASA Astrophysics Data System (ADS)

Timoney, Kevin; Lee, Peter

2016-04-01

Deltas form where riverborne sediment accumulates at the interface of river mouths and their receiving water bodies. Their areal extent is determined by the net effect of processes that increase their extent, such as sediment accumulation, and processes that decrease their extent, such as erosion and subsidence. Through sequential mapping and construction of river discharge and sediment histories, this study examined changes in the subaerial extents of the Cree Creek and Athabasca River Deltas (both on the Athabasca River system) and the Birch River Delta in northern Canada over the period 1950-2014. The purpose of the study was to determine how, when, and why the deltas changed in areal extent. Temporal growth patterns were similar across the Athabasca and Birch River systems indicative of a climatic signal. Little or no areal growth occurred from 1950 to 1968; moderate growth occurred between 1968 and the early to mid-1980s; and rapid growth occurred between 1992 and 2012. Factors that affected delta progradation included dredging, sediment supply, isostatic drowning, delta front bathymetry, sediment capture efficiency, and storms. In relation to sediment delivered, areal growth rates were lowest in the Athabasca Delta, intermediate in the Birch Delta, and highest in the Cree Creek Delta. Annual sediment delivery is increasing in the Cree Creek Delta; there were no significant trends in annual sediment delivery in the Birch and Athabasca Deltas. There was a lag of up to several years between sediment delivery events and progradation. Periods of delta progradation were associated with low water levels of the receiving basins. Predicted climate-change driven declines in river discharge and lake levels may accelerate delta progradation in the region. In the changing ecosystems of northeastern Alberta, inadequate monitoring of vegetation, landforms, and sediment regimes hampers the elucidation of the nature, rate, and causality of ecosystem changes.

Ganges River Delta, Bangladesh, India

NASA Image and Video Library

1994-11-14

The Ganges River Delta is the largest inter-tidal delta in the world. With its extensive mangrove mud flats, swamp vegetation and sand dunes, it is characteristic of many tropical and subtropical coasts. As seen in this photograph, the tributaries and distributaries of the Ganges and Brahmaputra Rivers deposit huge amounts of silt and clay that create a shifting maze of waterways and islands in the Bay of Bengal.

The wave-tide-river delta classification revisited: Introducing the effects of Humans on delta equilibriu

NASA Astrophysics Data System (ADS)

Besset, M.; Anthony, E.; Sabatier, F.

2016-12-01

The influence of physical processes on river deltas has long been identified, mainly on the basis of delta morphology. A cuspate delta is considered as wave-dominated, a delta with finger-like extensions is characterized as river-dominated, and a delta with estuarine re-entrants is considered tide-dominated (Galloway, 1975). The need for a more quantitative classification is increasingly recognized, and is achievable through quantified combinations, a good example being Syvitski and Saito (2007) wherein the joint influence of marine power - wave and tides - is compared to that of river influence. This need is further justified as deltas become more and more vulnerable. Going forward from the Syvitski and Saito (2007) approach, we confront, from a large database on 60 river deltas, the maximum potential power of waves and the tidal range (both representing marine power), and the specific stream power and river sediment supply reflecting an increasingly human-impacted river influence. The results show that 45 deltas (75%) have levels of marine power that are significantly higher than those of specific stream power. Five deltas have sufficient stream power to counterbalance marine power but a present sediment supply inadequate for them to be statistically considered as river-dominated. Six others have a sufficient sediment supply but a specific stream power that is not high enough for them to be statistically river-dominated. A major manifestation of the interplay of these parameters is accelerated delta erosion worldwide, shifting the balance towards marine power domination. Deltas currently eroding are mainly influenced by marine power (93%), and small deltas (< 300 km2 of deltaic protuberance) are the most vulnerable (82%). These high levels of erosion domination, compounded by accelerated subsidence, are related to human-induced sediment supply depletion and changes in water discharge in the face of the sediment-dispersive capacity of waves and currents.

Paraiba do Sul river delta, Brazil

NASA Image and Video Library

1996-01-20

STS072-738-019 (11-20 Jan. 1996) --- The Delta of the Paraiba do Sul River, northeast of Rio de Janeiro, Brazil, stands out in this 70mm frame exposed from the Earth-orbiting Space Shuttle Endeavour. The brown color of the river water and offshore sediment plume show that the river is in flood stage. This delta attracts much attention from orbit because of its prominent beach ridges either side of the river mouth. River sediment from inland supplies the material which is redistributed by coastal currents to form the parallel beach ridges. The lower 20 miles of the river appear in this scene. The river flows into the Atlantic in an easterly direction.

Evaluating geophysical lithology determination methods in the central offshore Nile Delta, Egypt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nada, H.; Shrallow, J.

1994-12-31

Two post stack and one prestack geophysical techniques were used to extract lithology and fluid information from seismic data. The purpose of this work was to evaluate the effectiveness of such methods in helping to find more hydrocarbons and reduce exploration risk in Egypt`s Nile Delta. Amplitude Variations with Offset (AVO) was used as a direct hydrocarbon indicator. CDP gathers were sorted into common angle gathers. The angle traces from 0--10 degrees were stacked to form a near angle stack and those from 30--40 degrees were stacked to form a far angle stack. Comparison of the far and near anglemore » stacks indicate areas which have seismic responses that match gas bearing sand models in the Pliocene and Messinian. Seismic Sequence Attribute mapping was used to measure the reflectivity of a seismic sequence. The specific sequence attribute measured in this study was the Maximum Absolute Amplitude of the seismic reflections within a sequence. Post stack seismic inversion was used to convert zero phase final migrated data to pseudo acoustic impedance data to interpret lithology from seismic data. All three methods are useful in the Nile Delta for identifying sand prone areas, but only AVO can be used to detect fluid content.« less

Subsidence driving forces in large Delta Plain

NASA Astrophysics Data System (ADS)

Grall, C.; Steckler, M. S.

2017-12-01

Recent studies show large variability in subsidence rates among large delta plains that directly impact coastal management of these highly vulnerable environments. Observations show both significant spatial variation in subsidence across each delta, as well as large differences in magnitude between different deltas. This variability raises the question of what are the driving forces that control subsidence in large delta plains that this study aims to address. Subsidence and sediment compaction is studied in 4 end-member large Delta Plains: the Ganges-Brahmaputra, the Mekong, the Mississippi and the Nile. Those large delta plains drastically contrast in subsidence rates (from values to several mm/yr to several cm/yr), in the nature of the sediment (notably in clay and organic matter content), and in the volume of sediment supplied by the large rivers that feed those coastal environments. The volume of sediment deposited in each delta plain during the Holocene is estimated and the compaction of the underlying sedimentary column is computed by using a backstripping approach. Sediment compaction behaviors are defined accordingly to the observed clay, silt and organic contents, and the rate of subsidence associated with compaction is determined. Results suggest that about 2/3 of observed Holocene subsidence may be associated with the mechanical and chemical compaction of the underlying sedimentary column due to the load of sediment deposited. The compaction appears to be significantly higher in delta plains characterized by a high sediment input and a high organic matter and clay content. Thus, the observed subsidence rates in the (muddy) Mekong delta appear to be one order of magnitude higher than other delta plains. In contrast, subsidence rates are modest in the Ganges-Brahmaputra, the Mississippi and the Nile delta plains, except away from the major rivers where deposits are muddier.

Serum Cadmium Levels in Pancreatic Cancer Patients from the East Nile Delta Region of Egypt

PubMed Central

Kriegel, Alison M.; Soliman, Amr S.; Zhang, Qing; El-Ghawalby, Nabih; Ezzat, Farouk; Soultan, Ahmed; Abdel-Wahab, Mohamed; Fathy, Omar; Ebidi, Gamal; Bassiouni, Nadia; Hamilton, Stanley R.; Abbruzzese, James L.; Lacey, Michelle R.; Blake, Diane A.

2006-01-01

The northeast Nile Delta region exhibits a high incidence of early-onset pancreatic cancer. It is well documented that this region has one of the highest levels of pollution in Egypt. Epidemiologic studies have suggested that cadmium, a prevalent pollutant in the northeast Nile Delta region, plays a role in the development of pancreatic cancer. Objective: We aimed to assess serum cadmium levels as markers of exposure in pancreatic cancer patients and noncancer comparison subjects from the same region in Egypt. Design and Participants: We assessed serum cadmium levels of 31 newly diagnosed pancreatic cancer patients and 52 hospital comparison subjects from Mansoura, Egypt. Evaluation/Measurements: Serum cadmium levels were measured using a novel immunoassay procedure. Results: We found a significant difference between the mean serum cadmium levels in patients versus comparison subjects (mean ± SD, 11.1 ± 7.7 ng/mL vs. 7.1 ± 5.0 ng/mL, respectively; p = 0.012) but not in age, sex, residence, occupation, or smoking status. The odds ratio (OR) for pancreatic cancer risk was significant for serum cadmium level [OR = 1.12; 95% confidence interval (CI), 1.04–1.23; p = 0.0089] and farming (OR = 3.25; 95% CI, 1.03–11.64; p = 0.0475) but not for age, sex, residence, or smoking status. Conclusions: The results from this pilot study suggest that pancreatic cancer in the East Nile Delta region is significantly associated with high levels of serum cadmium and farming. Relevance to Clinical Practice/Public Health: Future studies should further investigate the etiologic relationship between cadmium exposure and pancreatic carcinogenesis in cadmium-exposed populations. PMID:16393667

Growth laws for delta crevasses in the Mississippi River Delta: observations and modeling

NASA Astrophysics Data System (ADS)

Yocum, T. A.; Georgiou, I. Y.

2016-02-01

River deltas are accumulations of sedimentary deposits delivered by rivers via a network of distributary channels. Worldwide they are threatened by environmental changes, including subsidence, global sea level rise and a suite of other local factors. In the Mississippi River Delta (MRD) these impacts are exemplified, and have led to proposed solutions to build land that include sediment diversions, thereby reinitiating the delta cycle. While economically efficient, there are too few analogs of small deltas aside from laboratory studies, numerical modeling studies, theoretical approaches, and limited field driven observations. Anthropogenic crevasses in the modern delta are large enough to overcome limitations of laboratory deltas, and small enough to allow for "rapid" channel and wetland development, providing an ideal setting to investigate delta development mechanics. Crevasse metrics were obtained using a combination of geospatial tools, extracting key parameters (bifurcation length and width, channel order and depth) that were non-dimensionalized and compared to river-dominated delta networks previously studied. Analysis showed that most crevasses in the MRD appear to obey delta growth laws and delta allometry relationships, suggesting that crevasses do exhibit similar planform metrics to larger Deltas; the distance to mouth bar versus bifurcation order demonstrated to be a very reasonable first order estimate of delta-top footprint. However, some crevasses exhibited different growth metrics. To better understand the hydrodynamic and geomorphic controls governing crevasse evolution in the MRD, we assess delta dynamics via a suite of field observations and numerical modeling in both well-established and newly constructed crevasses. Our analysis suggests that delta development is affected by the relative influence of external (upstream and downstream) and internal controls on the hydrodynamic and sediment transport patterns in these systems.

Morphological changes of Gumara River channel over 50 years, upper Blue Nile basin, Ethiopia

NASA Astrophysics Data System (ADS)

Abate, Mengiste; Nyssen, Jan; Steenhuis, Tammo S.; Moges, Michael M.; Tilahun, Seifu A.; Enku, Temesgen; Adgo, Enyew

2015-06-01

In response to anthropogenic disturbances, alluvial rivers adjust their geometry. The alluvial river channels in the upper Blue Nile basin have been disturbed by human-induced factors since a longtime. This paper examines channel adjustment along a 38-km stretch of the Gumara River which drains towards Lake Tana and then to the Blue Nile. Over a 50 years period, agriculture developed rapidly in the catchment and flooding of the alluvial plain has become more frequent in recent times. The objectives of this study were to document the changes in channel planform and cross-section of the Gumara River and to investigate whether the changes could have contributed to the frequent flooding or vice versa. Two sets of aerial photographs (1957 and 1980) were scanned, and then orthorectified. Recent channel planform information was extracted from SPOT images of 2006 and Google Earth. Channel planform and bed morphology (vertical changes) were determined for these nearly 50 years period. The vertical changes were determined based on aggradation along a permanent structure, historic information on river cross-sections at a hydrological gauging station, and field observations. The results indicate that the lower reach of Gumara near its mouth has undergone major planform changes. A delta with approx. 1.12 km2 of emerged land was created between 1957 and 1980 and an additional 1 km2 of land has been added between 1980 and 2006. The sinuosity of the river changed only slightly: negatively (-1.1% i.e. meandering decreased) for the period from 1957 to 1980 and positively (+3.0%) for the period 1980-2006. Comparison of cross-sections at the hydrological gauging station showed that the deepest point in the river bed aggraded by 2.91 m for the period 1963-2009. The importance of sediment deposition in the stream and on its banks is related to land degradation in the upper catchment, and to artificial rising of Lake Tana level that creates a backwater effect and sediment deposition in

City Lights Illuminate the Nile

NASA Image and Video Library

2017-12-08

NASA image acquired October 13, 2012 The Nile River Valley and Delta comprise less than 5 percent of Egypt’s land area, but provide a home to roughly 97 percent of the country’s population. Nothing makes the location of human population clearer than the lights illuminating the valley and delta at night. On October 13, 2012, the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured this nighttime view of the Nile River Valley and Delta. This image is from the VIIRS “day-night band,” which detects light in a range of wavelengths from green to near-infrared and uses filtering techniques to observe signals such as gas flares, auroras, wildfires, city lights, and reflected moonlight. The city lights resemble a giant calla lily, just one with a kink in its stem near the city of Luxor. Some of the brightest lights occur around Cairo, but lights are abundant along the length of the river. Bright city lights also occur along the Suez Canal and around Tel Aviv. Away from the lights, however, land and water appear uniformly black. This image was acquired near the time of the new Moon, and little moonlight was available to brighten land and water surfaces. NASA Earth Observatory image by Jesse Allen and Robert Simmon, using VIIRS Day-Night Band data from the Suomi National Polar-orbiting Partnership. Suomi NPP is the result of a partnership between NASA, the National Oceanic and Atmospheric Administration, and the Department of Defense. Caption by Michon Scott. Instrument: Suomi NPP - VIIRS Credit: NASA Earth Observatory Click here to view all of the Earth at Night 2012 images Click here to read more about this image NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency�

Mississippi River Delta, Louisiana as seen from STS-62

NASA Image and Video Library

1994-03-05

STS062-85-021 (4-18 March 1994) --- The Mississippi River is the largest river system in North America. Its delta is a typical example of the bird's foot class of river deltas. It drains nearly 3 1/2 million square kilometers of real estate and is estimated to carry 2.4 billion kilograms (more than 500 million tons) of sand, silt, and clay to the Gulf of Mexico annually. Most of this sediment is deposited as a delta at the mouth of the river where the velocity of the river water is slowed and its ability to transport sediment is accordingly diminished. Continued deposition at such a site progrades the delta or extends it seaward into the Gulf as much as 150 meters each year until such time as a flooding episode finds a shorter more efficient channel to deliver sediment-laden river waters to the Gulf. At that time the old delta is abandoned and the river begins to build a new delta. In time, compaction of the sediment in the old delta causes it to subside forming first marshes, then bays. This and the modifying effects of coastal waves eventually allow the sea to reclaim much of the temporary land area of the delta. This sequence has repeated itself over and over again at the Mississippi Delta. In this photograph, the present day active Balize delta is shown. According to NASA scientists it is the youngest of the recent delta lobes having begun its seaward pro-gradation only some 600 - 800 years ago. The main channel of the river is 2 kilometers wide and 30 - 40 meters deep. Natural levees here are almost 1 kilometer wide and 3 to 4 meters above sea level. Along the active distributaries of the lower delta, natural levees are less than 100 meters wide and generally less than 0.5 meters above sea level. The bird's foot appearance of deltas such as this is characteristic of low coastal energy conditions - that is, low levels of tidal fluctuation and generally low wave energy. The interdistributary bays are extremely shallow, usually less than a few meters, and contain

Occurrence of pesticides in fish tissues, water and soil sediment from Manzala Lake and River Nile.

PubMed

Osfor, M M; Abd el Wahab, A M; el Dessouki, S A

1998-02-01

Pesticides constitute the major source of potential environmental hazard to man and animal as they are present and concentrated in the food chain. This study was conducted on 136 samples of water, sediment and fish for detection and determination of pesticide residues in this ecosystem. Highly significant differences were found in levels of Indian, heptachlor, endrin, dieldrin, P,P'-DDE and propoxur in River Nile water when compared with that of Manzala Lake. Levels of Indian, endrin, malathion and diazinon were significantly higher in soil sediment of Manzala Lake, while the levels of heptachlor, aldrine, P,P'-DDE, DDT, parathion, propoxur and zectran were significantly higher in soil sediment of River Nile. Boury fish of Manzala Lake contained higher levels of heptachlor, aldrin, P,P'-DDE and malathion, while boury fish of River Nile contained a higher level of zectran only. This survey, thus indicated that Manzala Lake and even the River Nile which was used as control are heavily contaminated with chlorinated hydrocarbons (Indian, heptachlor, aldrin, endrin, dieldrin, P,P'-DDE and DDT), organic phosphorus compounds (malathion, dimethoat, diazinon and parathion) and carbamate pesticides (propoxur and zectran).

Water Management Strategy in Assessing the Water Scarcity in Northern Western Region of Nile Delta, Egypt

NASA Astrophysics Data System (ADS)

Mabrouk, Badr; Arafa, Salah; Gemajl, Khaled

2015-04-01

Sustainable development in the Nile Delta of Egypt is retarded by serious environmental problems, where land-use and land-cover of the region are subjected to continuous changes; including shoreline changes either by erosion or accretion, subsidence of the delta, as well as by sea level rise due to climate change. The current research attempts to; (1) study the vulnerability of the northern western region of the Nile Delta coastal zone to climate change/sea level rise while setting basic challenges, review adaptation strategies based on adaptation policy framework, and highlight recommended programs for preparedness to climate change, (2) study the scarcity of water resources in the area of study with review of the socioeconomic impacts and the critical need of establishing desalination plants with new standards assessing the environmental situation and population clusters, and (3) monitor of the brine water extracted from the desalination plants and injected to subsurface strata. This monitoring process is divided into 3 main directions: 1) studying the chemical characteristics of water extracted from the water desalinations plants qualitatively and quantitatively. 2) mapping the subsurface of which that brine water will be injected to it and the flow directions and effects using resistivity data, and 3) using GIS and suitable numerical models in order to study the effect, volume, flow of the brine water and its long term environmental impacts on the area. The results indicate that the area is particularly vulnerable to the impact of SLR, salt water intrusion, the deterioration of coastal tourism and the impact of extreme dust storms. This in turn will directly affect the agricultural productivity and human settlements in coastal zones. The paper presents different scenarios for water management and recommends the most suitable scenarios in order to establish a core for water management strategy in the region according to existing socio-economic and environmental

Nile River, Lake Nasser, Aswan High Dam, Egypt, Africa

NASA Technical Reports Server (NTRS)

1992-01-01

Lake Nasser, (24.0N, 33.0E) at the Aswan High Dam on the Nile River, in Egypt is the world's second largest artificial lake, extending 500 km, in length and about 5000 sq. km. in area. The lake has a storage capacity sufficient to irrigate farms in Egypt and Sudan year round allowing up to three harvests per year. Other benefits include year round river navagation, hydroelectric power, more fish harvests, reduced flooding and more industrial employment. opportunites.

Origin of the Sinai-Negev erg, Egypt and Israel: mineralogical and geochemical evidence for the importance of the Nile and sea level history

USGS Publications Warehouse

Muhs, Daniel R.; Roskin, Joel; Tsoar, Haim; Skipp, Gary; Budahn, James R.; Sneh, Amihai; Porat, Naomi; Stanley, Jean-Daniel; Katra, Itzhak; Blumberg, Dan G.

2013-01-01

The Sinai–Negev erg occupies an area of 13,000 km2 in the deserts of Egypt and Israel. Aeolian sand of this erg has been proposed to be derived from the Nile Delta, but empirical data supporting this view are lacking. An alternative source sediment is sand from the large Wadi El Arish drainage system in central and northern Sinai. Mineralogy of the Negev and Sinai dunes shows that they are high in quartz, with much smaller amounts of K-feldspar and plagioclase. Both Nile Delta sands and Sinai wadi sands, upstream of the dunes, also have high amounts of quartz relative to K-feldspar and plagioclase. However, Sinai wadi sands have abundant calcite, whereas Nile Delta sands have little or no calcite. Overall, the mineralogical data suggest that the dunes are derived dominantly from the Nile Delta, with Sinai wadi sands being a minor contributor. Geochemical data that proxy for both the light mineral fraction (SiO2/10–Al2O3 + Na2O + K2O–CaO) and heavy mineral fraction (Fe2O3–MgO–TiO2) also indicate a dominant Nile Delta source for the dunes. Thus, we report here the first empirical evidence that the Sinai–Negev dunes are derived dominantly from the Nile Delta. Linkage of the Sinai–Negev erg to the Nile Delta as a source is consistent with the distribution of OSL ages of Negev dunes in recent studies. Stratigraphic studies show that during the Last Glacial period, when dune incursions in the Sinai–Negev erg began, what is now the Nile Delta area was characterized by a broad, sandy, minimally vegetated plain, with seasonally dry anastomosing channels. Such conditions were ideal for providing a ready source of sand for aeolian transport under what were probably much stronger glacial-age winds. With the post-glacial rise in sea level, the Nile River began to aggrade. Post-glacial sedimentation has been dominated by fine-grained silts and clays. Thus, sea level, along with favorable climatic conditions, emerges as a major influence on the timing of dune

From source to sink: Exploring the Quaternary history of the Nile

NASA Astrophysics Data System (ADS)

Woodward, J. C.; Williams, M. A. J.; Garzanti, E.; Macklin, M. G.; Marriner, N.

2015-12-01

Nearly two thousand five hundred years have elapsed since the Greek historian Herodotus (ca. 485-425 BC) posed a number of fundamental questions about the source, age, and flood regime of the River Nile. Herodotus travelled widely in Egypt in around 450 BC - mainly in the Delta and Lower Egypt, but he may have journeyed as far upstream as Aswan and the First Cataract. A keen observer of nature, with a questioning intellect, Herodotus very quickly discerned that the dark alluvial soils of Egypt were very different from the desert soils of Syria and Libya, and inferred that they were derived from the Ethiopian headwaters of the Nile. Herodotus was the first to recognize that Egyptian civilization was, as he put it, ;the gift of the river; (Griffiths, 1966) since he understood that, without the regular and reliable hundred days of flooding during the summer months, and the annual deposition of silts along the floodplains, agriculture would not have been possible on any significant scale under the desert climate of the Nile Valley.

Ganges River Delta

NASA Technical Reports Server (NTRS)

2002-01-01

The Ganges River forms an extensive delta where it empties into the Bay of Bengal. The delta is largely covered with a swamp forest known as the Sunderbans, which is home to the Royal Bengal Tiger. It is also home to most of Bangladesh, one of the world's most densely populated countries. Roughly 120 million people live on the Ganges Delta under threat of repeated catastrophic floods due to heavy runoff of meltwater from the Himalayas, and due to the intense rainfall during the monsoon season. This image was acquired by Landsat 7's Enhanced Thematic Mapper plus (ETM+) sensor on February 28, 2000. This is a false-color composite image made using green, infrared, and blue wavelengths. Image provided by the USGS EROS Data Center Satellite Systems Branch

Hydroclimate variability in the Nile River Basin during the past 28,000 years

NASA Astrophysics Data System (ADS)

Castañeda, Isla S.; Schouten, Stefan; Pätzold, Jürgen; Lucassen, Friedrich; Kasemann, Simone; Kuhlmann, Holger; Schefuß, Enno

2016-03-01

It has long been known that extreme changes in North African hydroclimate occurred during the late Pleistocene yet many discrepancies exist between sites regarding the timing, duration and abruptness of events such as Heinrich Stadial (HS) 1 and the African Humid Period (AHP). The hydroclimate history of the Nile River is of particular interest due to its lengthy human occupation history yet there are presently few continuous archives from the Nile River corridor, and pre-Holocene studies are rare. Here we present new organic and inorganic geochemical records of Nile Basin hydroclimate from an eastern Mediterranean (EM) Sea sediment core spanning the past 28 ka BP. Our multi-proxy records reflect the fluctuating inputs of Blue Nile versus White Nile material to the EM Sea in response to gradual changes in local insolation and also capture abrupt hydroclimate events driven by remote climate forcings, such as HS1. We find strong evidence for extreme aridity within the Nile Basin evolving in two distinct phases during HS1, from 17.5 to 16 ka BP and from 16 to 14.5 ka BP, whereas peak wet conditions during the AHP are observed from 9 to 7 ka BP. We find that zonal movements of the Congo Air Boundary (CAB), and associated shifts in the dominant moisture source (Atlantic versus Indian Ocean moisture) to the Nile Basin, likely contributed to abrupt hydroclimate variability in northern East Africa during HS1 and the AHP as well as to non-linear behavior of hydroclimate proxies. We note that different proxies show variable gradual and abrupt responses to individual hydroclimate events, and thus might have different inherent sensitivities, which may be a factor contributing to the controversy surrounding the abruptness of past events such as the AHP. During the Late Pleistocene the Nile Basin experienced extreme hydroclimate fluctuations, which presumably impacted Paleolithic cultures residing along the Nile corridor.

From Natural to Design River Deltas

NASA Astrophysics Data System (ADS)

Giosan, Liviu

2016-04-01

Productive and biologically diverse, deltaic lowlands attracted humans since prehistory and may have spurred the emergence of the first urban civilizations. Deltas continued to be an important nexus for economic development across the world and are currently home for over half a billion people. But recently, under the double whammy of sea level rise and inland sediment capture behind dams, they have become the most threatened coastal landscape. Here I will address several deceptively simple questions to sketch some unexpected answers using example deltas from across the world from the Arctic to the Tropics, from the Danube to the Indus, Mississippi to Godavari and Krishna, Mackenzie to Yukon. What is a river delta? What is natural and what is not in a river delta? Are the geological and human histories of a delta important for its current management? Is maintaining a delta the same to building a new one? Can we design better deltas than Nature? These answers help us see clearly that survival of deltas in the next century depends on human intervention and is neither assured nor simple to address or universally applicable. Empirical observations on the hydrology, geology, biology and biochemistry of deltas are significantly lagging behind modeling capabilities endangering the applicability of numerical-based reconstruction solutions and need to be ramped up significantly and rapidly across the world.

Connectivity in river deltas

NASA Astrophysics Data System (ADS)

Passalacqua, P.; Hiatt, M. R.; Sendrowski, A.

2016-12-01

Deltas host approximately half a billion people and are rich in ecosystem diversity and economic resources. However, human-induced activities and climatic shifts are significantly impacting deltas around the world; anthropogenic disturbance, natural subsidence, and eustatic sea-level rise are major causes of threat to deltas and in many cases have compromised their safety and sustainability, putting at risk the people that live on them. In this presentation, I will introduce a framework called Delta Connectome for studying connectivity in river deltas based on different representations of a delta as a network. Here connectivity indicates both physical connectivity (how different portions of the system interact with each other) as well as conceptual (pathways of process coupling). I will explore several network representations and show how quantifying connectivity can advance our understanding of system functioning and can be used to inform coastal management and restoration. From connectivity considerations, the delta emerges as a leaky network that evolves over time and is characterized by continuous exchanges of fluxes of matter, energy, and information. I will discuss the implications of connectivity on delta functioning, land growth, and potential for nutrient removal.

Lake Nasser on Nile River in Egypt as seen from the Apollo 7 spacecraft

NASA Image and Video Library

1968-10-12

Lake Nasser on the Nile River in southeastern United Arab Republic (Egypt) as seen from the Apollo 7 spacecraft during its 10th revolution of the earth. Photographed from an altitude of 130 nautical miles, at ground elapsed time of 14 hours and 56 minutes. Lake Nasser was created by the contruction of the Aswan Dam on the Nile.

Wetland vegetation in Manzala lagoon, Nile Delta coast, Egypt: Rapid responses of pollen to altered nile hydrology and land use

USGS Publications Warehouse

Bernhardt, C.E.; Stanley, J.-D.; Horton, B.P.

2011-01-01

The pollen record in a sediment core from Manzala lagoon on the Nile delta coastal margin of Egypt, deposited from ca. AD 1860 to 1990, indicates rapid coastal wetland vegetation responses to two primary periods of human activity. These are associated with artificially altered Nile hydrologic regimes in proximal areas and distal sectors located to ???1200 km south of Manzala. Freshwater wetland plants that were dominant, such as Typha and Phragmites, decreased rapidly, whereas in the early 1900s, brackish water wetland species (e.g., Amaranthaceae) increased. This change occurred after closure of the Aswan Low Dam in 1902. The second major modification in the pollen record occurred in the early 1970s, after Aswan High Dam closure from 1965 to 1970, when Typha pollen abundance increased rapidly. Massive population growth occurred along the Nile during the 130 years represented by the core section. During this time, the total volume of lagoon water decreased because of conversion of wetland areas to agricultural land, and input of organic-rich sediment, sewage (municipal, agricultural, industrial), and fertilizer in Manzala lagoon increased markedly. Although the wetland plant community has continued to respond to increasingly intensified and varied human-induced pressures in proximal sectors, the two most marked changes in Manzala pollen best correlate with distal events (i.e., closure of the two dams at Aswan). The study also shows that the two major vegetation changes in Manzala lagoon each occurred less than 10 years after closure upriver of the Low and High dams that markedly altered the Nile regime from Upper Egypt to the coast. ?? 2011, the Coastal Education & Research Foundation (CERF).

Tidal river dynamics: Implications for deltas

NASA Astrophysics Data System (ADS)

Hoitink, A. J. F.; Jay, D. A.

2016-03-01

Tidal rivers are a vital and little studied nexus between physical oceanography and hydrology. It is only in the last few decades that substantial research efforts have been focused on the interactions of river discharge with tidal waves and storm surges into regions beyond the limit of salinity intrusion, a realm that can extend inland hundreds of kilometers. One key phenomenon resulting from this interaction is the emergence of large fortnightly tides, which are forced long waves with amplitudes that may increase beyond the point where astronomical tides have become extinct. These can be larger than the linear tide itself at more landward locations, and they greatly influence tidal river water levels and wetland inundation. Exploration of the spectral redistribution and attenuation of tidal energy in rivers has led to new appreciation of a wide range of consequences for fluvial and coastal sedimentology, delta evolution, wetland conservation, and salinity intrusion under the influence of sea level rise and delta subsidence. Modern research aims at unifying traditional harmonic tidal analysis, nonparametric regression techniques, and the existing understanding of tidal hydrodynamics to better predict and model tidal river dynamics both in single-thread channels and in branching channel networks. In this context, this review summarizes results from field observations and modeling studies set in tidal river environments as diverse as the Amazon in Brazil, the Columbia, Fraser and Saint Lawrence in North America, the Yangtze and Pearl in China, and the Berau and Mahakam in Indonesia. A description of state-of-the-art methods for a comprehensive analysis of water levels, wave propagation, discharges, and inundation extent in tidal rivers is provided. Implications for lowland river deltas are also discussed in terms of sedimentary deposits, channel bifurcation, avulsion, and salinity intrusion, addressing contemporary research challenges.

A global deltas typology of environmental stress and its relation to terrestrial hydrology

NASA Astrophysics Data System (ADS)

Tessler, Z. D.; Vorosmarty, C. J.; McDonald, K. C.; Schroeder, R.; Grossberg, M.; Gladkova, I.; Aizenman, H.

2013-12-01

River delta systems around the world are under varying degrees of environmental stress stemming from a variety of human impacts, both from upstream basin based activities and local impacts on the deltas themselves, as well as sea level rise. These stresses are known to affect rates of relative sea level rise by disrupting the delivery or deposition of sediment on the delta. We present a global database of several of these stresses, and investigate patterns of stress across delta systems. Several methods of aggregating the environmental stressors into an index score are also investigated. A statistical clustering analysis, which we refer to as a "global delta fingerprinting system", across the environmental stresses identifies systems under similar states of threat. Several deltas, including the Nile, are in unique clusters, while regional patterns are evident among deltas in Southeast Asia. These patterns are compared with observed surface inundation derived from SAR, NDVI from MODIS, river discharge estimates from the WBMplus numerical model, and ocean wave activity from WAVEWATCH III. Delta inundation sensitivity to river and coastal forcings are observed to vary with environmental stress and social indicators including population density and GDP.

River water quality and pollution sources in the Pearl River Delta, China.

PubMed

Ouyang, Tingping; Zhu, Zhaoyu; Kuang, Yaoqiu

2005-07-01

Some physicochemical parameters were determined for thirty field water samples collected from different water channels in the Pearl River Delta Economic Zone river system. The analytical results were compared with the environmental quality standards for surface water. Using the SPSS software, statistical analyses were performed to determine the main pollutants of the river water. The main purpose of the present research is to investigate the river water quality and to determine the main pollutants and pollution sources. Furthermore, the research provides some approaches for protecting and improving river water quality. The results indicate that the predominant pollutants are ammonium, phosphorus, and organic compounds. The wastewater discharged from households in urban and rural areas, industrial facilities, and non-point sources from agricultural areas are the main sources of pollution in river water in the Pearl River Delta Economic Zone.

Experimental river delta size set by multiple floods and backwater hydrodynamics.

PubMed

Ganti, Vamsi; Chadwick, Austin J; Hassenruck-Gudipati, Hima J; Fuller, Brian M; Lamb, Michael P

2016-05-01

River deltas worldwide are currently under threat of drowning and destruction by sea-level rise, subsidence, and oceanic storms, highlighting the need to quantify their growth processes. Deltas are built through construction of sediment lobes, and emerging theories suggest that the size of delta lobes scales with backwater hydrodynamics, but these ideas are difficult to test on natural deltas that evolve slowly. We show results of the first laboratory delta built through successive deposition of lobes that maintain a constant size. We show that the characteristic size of delta lobes emerges because of a preferential avulsion node-the location where the river course periodically and abruptly shifts-that remains fixed spatially relative to the prograding shoreline. The preferential avulsion node in our experiments is a consequence of multiple river floods and Froude-subcritical flows that produce persistent nonuniform flows and a peak in net channel deposition within the backwater zone of the coastal river. In contrast, experimental deltas without multiple floods produce flows with uniform velocities and delta lobes that lack a characteristic size. Results have broad applications to sustainable management of deltas and for decoding their stratigraphic record on Earth and Mars.

Experimental river delta size set by multiple floods and backwater hydrodynamics

PubMed Central

Ganti, Vamsi; Chadwick, Austin J.; Hassenruck-Gudipati, Hima J.; Fuller, Brian M.; Lamb, Michael P.

2016-01-01

River deltas worldwide are currently under threat of drowning and destruction by sea-level rise, subsidence, and oceanic storms, highlighting the need to quantify their growth processes. Deltas are built through construction of sediment lobes, and emerging theories suggest that the size of delta lobes scales with backwater hydrodynamics, but these ideas are difficult to test on natural deltas that evolve slowly. We show results of the first laboratory delta built through successive deposition of lobes that maintain a constant size. We show that the characteristic size of delta lobes emerges because of a preferential avulsion node—the location where the river course periodically and abruptly shifts—that remains fixed spatially relative to the prograding shoreline. The preferential avulsion node in our experiments is a consequence of multiple river floods and Froude-subcritical flows that produce persistent nonuniform flows and a peak in net channel deposition within the backwater zone of the coastal river. In contrast, experimental deltas without multiple floods produce flows with uniform velocities and delta lobes that lack a characteristic size. Results have broad applications to sustainable management of deltas and for decoding their stratigraphic record on Earth and Mars. PMID:27386534

Epidemiology of bovine fascioliasis in the Nile Delta region of Egypt: Its prevalence, evaluation of risk factors, and its economic significance

PubMed Central

El-Tahawy, Abdelgawad S.; Bazh, Eman K.; Khalafalla, Reda E.

2017-01-01

Aim: This study focuses on the risk factors associated with the prevalence of Fasciola affecting cattle population in three provinces belonging to the Nile Delta of Egypt and to estimate the economic losses as a result of fascioliasis. Materials and Methods: From January 2015 to end of December 2015, records of 21 farms (4976 cattle) were analyzed to screen the prevalence of fascioliasis among cattle farms, to identify its associated risk factors and its economic impacts on Nile Delta region of Egypt. Results: The overall prevalence of fascioliasis in the Nile Delta region of Egypt was 9.77%. The prevalence of fascioliasis was found to be statistically significantly associated with age, sex, breed, and type of farms. The highest prevalence was observed in <2 age group (10.91%), and the lowest was >3 age groups (8.35%). In terms of body condition scores, cattle with medium and poor conditions were associated with fascioliasis more than those with good body condition. Besides, cattle raised in organic farms were associated with lower risk of fascioliasis than those in conventional farms. The prevalence of fascioliasis was noted more prominent in districts with moderate temperatures and with relative humidity (>60%). The annual overall costs for fascioliasis were estimated to be 221.2 USD/cow due to the significant reduction in body weight, reduction in milk production, and the treatment costs for fascioliasis. Conclusion: The results provided could be helpful for improving the control and preventive strategies. PMID:29184371

Epidemiology of bovine fascioliasis in the Nile Delta region of Egypt: Its prevalence, evaluation of risk factors, and its economic significance.

PubMed

El-Tahawy, Abdelgawad S; Bazh, Eman K; Khalafalla, Reda E

2017-10-01

This study focuses on the risk factors associated with the prevalence of Fasciola affecting cattle population in three provinces belonging to the Nile Delta of Egypt and to estimate the economic losses as a result of fascioliasis. From January 2015 to end of December 2015, records of 21 farms (4976 cattle) were analyzed to screen the prevalence of fascioliasis among cattle farms, to identify its associated risk factors and its economic impacts on Nile Delta region of Egypt. The overall prevalence of fascioliasis in the Nile Delta region of Egypt was 9.77%. The prevalence of fascioliasis was found to be statistically significantly associated with age, sex, breed, and type of farms. The highest prevalence was observed in <2 age group (10.91%), and the lowest was >3 age groups (8.35%). In terms of body condition scores, cattle with medium and poor conditions were associated with fascioliasis more than those with good body condition. Besides, cattle raised in organic farms were associated with lower risk of fascioliasis than those in conventional farms. The prevalence of fascioliasis was noted more prominent in districts with moderate temperatures and with relative humidity (>60%). The annual overall costs for fascioliasis were estimated to be 221.2 USD/cow due to the significant reduction in body weight, reduction in milk production, and the treatment costs for fascioliasis. The results provided could be helpful for improving the control and preventive strategies.

Nile Delta exhibited a spatial reversal in the rates of shoreline retreat on the Rosetta promontory comparing pre- and post-beach protection

NASA Astrophysics Data System (ADS)

Ghoneim, Eman; Mashaly, Jehan; Gamble, Douglas; Halls, Joanne; AbuBakr, Mostafa

2015-01-01

The coastline of the Nile Delta experienced accelerated erosion since the construction of the Aswan High Dam in 1964 and, consequently, the entrapment of a large amount of river sediments behind it. The coastline of the Rosetta promontory showed the highest erosion in the Delta with an average retreat rate of 137.4 m year- 1. In 1991, in an effort to mitigate sediment loss, a 4.85 km long seawall was built on the outer margin of the promontory. For additional beach protection, 15 groins were constructed along the eastern and western sides of the seawall in 2003 and 2005. To quantify erosion and accretion patterns along the Rosetta promontory, 11 Landsat images acquired at unequal intervals during a 40 year time span (1972 and 2012) were analyzed. The positions of shorelines were automatically extracted from satellite imagery and compared with three very high resolution QuickBird and WorldView2 images for data validation. Analysis of the rates of shoreline change revealed that the construction of the seawall was largely successful in halting the recession along the tip of the promontory, which lost 10.8 km2 prior to coastal protection. Conversely, the construction of the 15 groins has negatively affected the coastal morphology of the promontory and caused a reversal from accretion to fast erosion along the promontory leeside, where some segments of the shoreline have undergone as much as 30.8 m year- 1 of erosion. Without hard structures, the tip of the Rosetta promontory would have retreated 2.3 km by 2013 and lost 7.2 km2 of land. About 10% of this land is deltaic fertile cultivated farms. Moreover, without additional protection the sides of the promontory will lose about 1.3 km2 of land and the coastline would recede at an average rate of 200 m by 2020. Unless action is taken, coastal erosion, enhanced by rising sea level, will steadily eat away the Nile Delta at an alarming rate. The successful demonstration of the advocated procedures in this study could be

Predictability of current and future multi-river discharges: Ganges, Brahmaputra, Yangtze, Blue Nile, and Murray-Darling rivers

NASA Astrophysics Data System (ADS)

Jian, Jun

2007-12-01

Determining river discharge is of critical importance to many societies as they struggle with fresh water supply and risk of flooding. In Bangladesh, floods occur almost every year but with sufficient irregularity to have adverse social and economical consequences. Important goals are to predict the discharge to be used for the optimization of agricultural practices, disaster mitigation and water resource management. The aim of this study is to determine the predictability of river discharge in a number of major rivers on time scale varying from weeks to a century. We investigated predictability considering relationship between SST and discharge. Next, we consider IPCC model projections of river discharge while the models are statistically adjusted against observed discharges. In this study, we consider five rivers, the Ganges, the Brahmaputra, the Yangtze, the Blue Nile, and the Murray-Darling Rivers. On seasonal time scales, statistically significant correlations are found between mean monthly equatorial Pacific sea surface temperature (SST) and the summer Ganges discharge with lead times of 2-3 months due to oscillations of the El Nino-Southern Oscillation (ENSO) phenomena. In addition, there are strong correlations in the southwest and northeast Pacific. These, too, appear to be tied to the ENSO cycle. The Brahmaputra discharge, on the other hand, shows somewhat weaker relationships with tropical SST. Strong lagged correlations relationships are found with SST in the Bay of Bengal but these are the result of very warm SSTs and exceptional Brahmaputra discharge during the summer of 1998. When this year is removed from the time series, relationships weaken everywhere except in the northwestern Pacific for the June discharge and in areas of the central Pacific straddling the equator for the July discharge. The relationships are relative strong, but they are persistent from month to month and suggest that two different and sequential factors influence Brahmaputra

Seismic stability of the Duwamish River Delta, Seattle, Washington

USGS Publications Warehouse

Kayen, Robert E.; Barnhardt, Walter A.

2007-01-01

The delta front of the Duwamish River valley near Elliott Bay and Harbor Island is founded on young Holocene deposits shaped by sea-level rise, episodic volcanism, and seismicity. These river-mouth deposits are highly susceptible to seismic soil liquefaction and are potentially prone to submarine landsliding and disintegrative flow failure. A highly developed commercial-industrial corridor, extending from the City of Kent to the Elliott Bay/Harbor Island marine terminal facilities, is founded on the young Holocene deposits of the Duwamish River valley. The deposits of this Holocene delta have been shaped not only by relative sea-level rise but also by episodic volcanism and seismicity. Ground-penetrating radar (GPR), cores, in situ testing, and outcrops are being used to examine the delta stratigraphy and to infer how these deposits will respond to future volcanic eruptions and earthquakes in the region. A geotechnical investigation of these river-mouth deposits indicates high initial liquefaction susceptibility during earthquakes, and possibly the potential for unlimited-strain disintegrative flow failure of the delta front.

Nile River, Lake Nasser, Aswan High Dam, Egypt

NASA Technical Reports Server (NTRS)

1992-01-01

The Aswan High Dam, 2.5 miles across and 364 feet high, (24.0N, 33.0E) completed in 1971, was constructed to supply cheap hydroelectric power to both Egypt and Sudan by impounding, controling and regulating the flood waters of the Nile River in Lake Nasser, the world's second largest artifical lake. The lake extends over 500 miles in length, covers an area of some 2,000 square miles and is as much as 350 feet deep at the face of the dam.

Mackenzie River Delta, Canada

NASA Technical Reports Server (NTRS)

2007-01-01

The Mackenzie River in the Northwest Territories, Canada, with its headstreams the Peace and Finley, is the longest river in North America at 4241 km, and drains an area of 1,805,000 square km. The large marshy delta provides habitat for migrating Snow Geese, Tundra Swans, Brant, and other waterfowl. The estuary is a calving area for Beluga whales. The Mackenzie (previously the Disappointment River) was named after Alexander Mackenzie who travelled the river while trying to reach the Pacific in 1789.

The image was acquired on August 4, 2005, covers an area of 55.8 x 55.8 km, and is located at 68.6 degrees north latitude, 134.7 degrees west longitude.

The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

Mineralogy and source rock evaluation of the marine Oligo-Miocene sediments in some wells in the Nile Delta and North Sinai, Egypt

NASA Astrophysics Data System (ADS)

El sheikh, Hassan; Faris, Mahmoud; Shaker, Fatma; Kumral, Mustafa

2016-06-01

This paper aims to study the mineralogical composition and determine the petroleum potential of source rocks of the Oligocene-Miocene sequence in the Nile Delta and North Sinai districts. The studied interval in the five wells can be divided into five rock units arranged from the top to base; Qawasim, Sidi Salem, Kareem, Rudeis, and Qantara formations. The bulk rock mineralogy of the samples was investigated using X-Ray Diffraction technique (XRD). The results showed that the sediments of the Nile Delta area are characterized by the abundance of quartz and kaolinite with subordinate amounts of feldspars, calcite, gypsum, dolomite, and muscovite. On the other hand, the data of the bulk rock analysis at the North Sinai wells showed that kaolinite, quartz, feldspar and calcite are the main constituents associated with minor amounts of dolomite, gypsum, mica, zeolite, and ankerite. Based on the organic geochemical investigations (TOC and Rock-Eval pyrolysis analyses), all studied formations in both areas are thermally immature but in the Nile delta area, Qawasim, Sidi Salem and Qantara formations (El-Temsah-2 Well) are organically-rich and have a good petroleum potential (kerogen Type II-oil-prone), while Rudeis Formation is a poor petroleum potential source rock (kerogen Type III-gas-prone). In the North Sinai area, Qantara Formation has a poor petroleum potential (kerogen Type III-gas-prone) and Sidi Salem Formation (Bardawil-1 Well) is a good petroleum potential source rock (kerogen Type II-oil-prone).

Sandy River Delta Habitat Restoration Project, Annual Report 2001.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kelly, Virginia; Dobson, Robin L.

The Sandy River Delta is located at the confluence of the Sandy and Columbia Rivers, just east of Troutdale, Oregon. It comprises about 1,400 land acres north of Interstate 84, managed by the USDA Forest Service, and associated river banks managed by the Oregon Division of State Lands. Three islands, Gary, Flag and Catham, managed by Metro Greenspaces and the State of Oregon lie to the east, the Columbia River lies to the north and east, and the urbanized Portland metropolitan area lies to the west across the Sandy River. Sandy River Delta was historically a wooded, riparian wetland withmore » components of ponds, sloughs, bottomland woodland, oak woodland, prairie, and low and high elevation floodplain. It has been greatly altered by past agricultural practices and the Columbia River hydropower system. Restoration of historic landscape components is a primary goal for this land. The Forest Service is currently focusing on restoration of riparian forest and wetlands. Restoration of open upland areas (meadow/prairie) would follow substantial completion of the riparian and wetland restoration. The Sandy River Delta is a former pasture infested with reed canary grass, blackberry and thistle. The limited over story is native riparian species such as cottonwood and ash. The shrub and herbaceous layers are almost entirely non-native, invasive species. Native species have a difficult time naturally regenerating in the thick, competing reed canary grass, Himalayan blackberry and thistle. A system of drainage ditches installed by past owners drains water from historic wetlands. The original channel of the Sandy River was diked in the 1930's, and the river diverted into the ''Little Sandy River''. The original Sandy River channel has subsequently filled in and largely become a slough. The FS acquired approximately 1,400 acres Sandy River Delta (SRD) in 1991 from Reynolds Aluminum (via the Trust for Public Lands). The Delta had been grazed for many years but shortly after

Godavari River Delta Panorama, Bay of Bengal, India

NASA Image and Video Library

1993-01-19

STS054-80-024 (13-19 Jan 1993) --- As the Shuttle was passing southeast over the coast of India, approaching the Bay of Bengal, Endeavour's crew took this picture of the Godavari River Delta. The sun glint pattern was centered directly over the delta and highlighted well the intricate drainage pattern. Offshore, water features associated with current boundaries and river plumes are readily visible. The line of clouds along the coast south of the delta suggest that surface winds are blowing onshore from the Bay of Bengal. As the air passes over the warmer coastal water and land, it is warmed and begins to rise. The moisture in the air condenses, forming a line of low-level clouds.

Apollo 9 Mission image - United Arab Republic,Nile River,Red Sea and Aswan Dam

NASA Image and Video Library

1969-03-03

Oblique Earth Observation taken by the Apollo 9 crew. View is the United Arab Republic,the Nile River,The Red Sea and the Aswan Dam. Film magazine was E,film type was SO-368 Ektachrome with 0.460 - 0.710 micrometers film / filter transmittance response and haze filter,80mm lens. Latitude was 19.38 N by Longitude 30.24 E, Overlap was 50%, Altitude was 97 nautical miles and cloud cover was 5%.

The Delta Connectome: A network-based framework for studying connectivity in river deltas

NASA Astrophysics Data System (ADS)

Passalacqua, Paola

2017-01-01

Many deltas, including the Mississippi River Delta, have been losing land at fast rates compromising the safety and sustainability of their ecosystems. Knowledge of delta vulnerability has raised global concern and stimulated active interdisciplinary research as deltas are densely populated landscapes, rich in agriculture, fisheries, oil and gas, and important means for navigation. There are many ways of looking at this problem which all contribute to a deeper understanding of the functioning of coastal systems. One aspect that has been overlooked thus far, yet fundamental for advancing delta science is connectivity, both physical (how different portions of the system interact with each other) as well as conceptual (pathways of process coupling). In this paper, I propose a framework called Delta Connectome for studying connectivity in river deltas based on different representations of a delta as a network. After analyzing the classic network representation as a set of nodes (e.g., bifurcations and junctions or regions with distinct physical or statistical behavior) and links (e.g., channels), I show that from connectivity considerations the delta emerges as a leaky network that continuously exchanges fluxes of matter, energy, and information with its surroundings and evolves over time. I explore each network representation and show through several examples how quantifying connectivity can bring to light aspects of deltaic systems so far unexplored and yet fundamental to understanding system functioning and informing coastal management and restoration. This paper serves both as an introduction to the Delta Connectome framework as well as a review of recent applications of the concepts of network and connectivity to deltaic systems within the Connectome framework.

Assessing and managing water scarcity within the Nile River Transboundary Basin

NASA Astrophysics Data System (ADS)

Butts, M. B.; Wendi, D.; Jessen, O. Z.; Riegels, N. D.

2012-04-01

The Nile Basin is the main source of water in the North Eastern Region of Africa and is perhaps one of the most critical river basins in Africa as the riparian countries constitute 40% of the population on the continent but only 10% of the area. This resource is under considerable stress with rising levels of water scarcity, high population growth, watershed degradation, and loss of environmental services. The potential impacts of climate change may significantly exacerbate this situation as the water resources in the Nile Basin are critically sensitive to climate change (Conway, Hanson, Doherty, & Persechino, 2007). The motivation for this study is an assessment of climate change impacts and adaptation potential for floods and droughts within the UNEP project "Adapting to climate change induced water stress in the Nile River Basin", supported by SIDA. This project is being carried out as collaboration between DHI, the UK Met Office, and the Nile Basin Initiative (NBI). The Nile Basin exhibits highly diverse climatological and hydrological characteristics. Thus climate change impacts and adaptive capacity must be addressed at both regional and sub-basin scales. While the main focus of the project is the regional scale, sub-basin scale modelling is required to reflect variability within the basin. One of the major challenges in addressing this variability is the scarcity of data. This paper presents an initial screening modelling study of the water balance of the Nile Basin along with estimates of expected future impacts of climate change on the water balance. This initial study is focussed on the Ethiopian Highlands and the Lake Victoria regions, where the impact of climate change on rainfall is important. A robust sub-basin based monthly water balance model is developed and applied to selected sub-basins. The models were developed and calibrated using publicly available data. One of the major challenges in addressing this variability within the basin is the

Holocene delta evolution and sediment discharge of the Mekong River, southern Vietnam

NASA Astrophysics Data System (ADS)

Ta, Thi Kim Oanh; Nguyen, Van Lap; Tateishi, Masaaki; Kobayashi, Iwao; Tanabe, Susumu; Saito, Yoshiki

2002-09-01

Evolutionary changes, delta progradation, and sediment discharge of the Mekong River Delta, southern Vietnam, during the late Holocene are presented based on detailed analyses of samples from six boreholes on the lower delta plain. Sedimentological and chronostratigraphic analyses indicate clearly that the last 3 kyr were characterized by delta progradation under increasing wave influence, southeastward sediment dispersal, decreasing progradation rates, beach-ridge formation, and steepening of the face of the delta front. Estimated sediment discharge of the Mekong River for the last 3 kyr, based on sediment-volume analysis, was 144±36 million t yr -1 on average, or almost the same as the present level. The constant rate of delta front migration and stable sediment discharge during the last 3 kyr indicate that a dramatic increase in sediment discharge owing to human activities, as has been suggested for the Yellow River watershed, did not occur. Although Southeast Asian rivers have been considered candidates for such dramatic increases in discharge during the last 2 kyr, the Mekong River example, although it is a typical, large river of this region, does not support this hypothesis. Therefore, estimates of the millennial-scale global pristine sediment flux to the oceans must be revised.

Shallow groundwater investigation using time-domain electromagnetic (TEM) method at Itay El-Baroud, Nile Delta, Egypt

NASA Astrophysics Data System (ADS)

Shaaban, H.; El-Qady, G.; Al-Sayed, E.; Ghazala, H.; Taha, A. I.

2016-12-01

The Nile Delta is one of the oldest known ancient delta, largest and most important depositional complex in the Mediterranean sedimentary basin. Furthermore, it is a unique site in Egypt that is suitable for accumulation and preservation of the Quaternary sediments. In this work we applied time-domain electromagnetic (TEM) method to investigate the Quaternary sediments sequence as well as detecting the groundwater aquifer in the area of study. A suite of 232 TEM sounding at 43 stations were carried out using a ;SIROTEM MK-3; time-domain electromagnetic system. A simple coincident loop configuration, in which the same loop transmits and receives signals, was employed with loop side length of 25 m. The 1-D modeling technique was applied to estimate the depth and the apparent resistivity of the interpreted geoelectrical data. Based on the interpretation of the acquired geophysical data, four geoelectric cross-sections were constructed. These sections show that the Upper Quaternary sequence consists of three geoelectric layers. The Holocene Nile mud is separated into two layers: the agricultural root zone (Layer 1) and thick water saturated mud (Layer 2). The Upper Pleistocene sandy aquifer (Layer 3) is very complicated non-linear boundary. This aquifer is the most important unit since it is considered as the main water bearing unit in the study area.

Hydro-economic Risk Assessment in the Eastern Nile River Basin

NASA Astrophysics Data System (ADS)

Arjoon, D.; Tilmant, A.; Mohamed, Y.

2013-12-01

In 2011, the Ethiopian government announced plans for the construction of the Grand Renaissance Dam (GRD) on the Blue Nile, just east of its border with Sudan, at a cost of almost 5 billion dollars. The project is expected to generate over 15 TWh of energy and will include a reservoir of more than 60 km3 capacity, which roughly corresponds to the average annual flow of the Blue Nile. This project is part of a larger scheme, by the government, to expand its hydroelectric power capacity, however, the scheme faces strong opposition from downstream Egypt and Sudan. Egypt and Sudan are highly dependent on flows that originate in Ethiopia (it has been estimated that 86% of Nile flow originates in the Ethiopian highlands). The Ethiopian government argues that the dam would supply electricity for Ethiopians as well as generate surplus energy for export to neighboring countries. The Ethiopians also argue that the huge reservoir would generate positive externalities downstream by reducing floods and providing more constant and predictable lows. This study attempts to provide an independent analysis of the hydrologic and economic risks faced by downstream countries when GRD will be online. To achieve this, an integrated, stochastic hydro-economic model of the entire Eastern Nile basin is used to analyze various development and management scenarios. The results indicate that if countries agree to co- operative management of the Eastern Nile River basin, GRD would indeed significantly increase basin-wide benefits, especially in Ethiopia and in Sudan. An alternative management scenario, whereby GRD would be operated by Sudan and Egypt, does not yield significant economic gains in these countries. However, massive unilateral irrigation developments in Ethiopia will be detrimental for all countries, including Ethiopia itself, due to the huge opportunity costs involved.

Water Security and Hydropolitics of the Nile River: South Sudan’s National Security in the 21st Century

DTIC Science & Technology

2011-12-16

Politics of the Nile Basin” (Master’s Thesis, University of Witwatersrand, Johannesburg, 2009). 2 While the Nile Basin is the longest trans- boundary ...conflicts, there may be an area of cooperation among states that share trans- boundary international river systems.32 Other staggering statistics on the...

Hugli River Delta, India

NASA Image and Video Library

2001-10-22

The western-most part of the Ganges Delta is seen in this 54.5 by 60 km ASTER sub-scene acquired on January 6, 2005. The Hugli River branches off from the Ganges River 300 km to the north, and flows by the city of Calcutta before emptying into the Bay of Bengal. High sediment load is evident by the light tan colors in the water, particularly downstream from off-shore islands. The deep green colors of some of these islands are mangrove swamps. The image is centered at 21.9 degrees north latitude, 88 degrees east longitude. http://photojournal.jpl.nasa.gov/catalog/PIA11158

Cohesive Sedimentary Processes on River-Dominated Deltas: New Perspectives from the Mississippi River Delta Front, Gulf of Mexico

NASA Astrophysics Data System (ADS)

Bentley, S. J.; Keller, G. P.; Obelcz, J.; Maloney, J. M.; Xu, K.; Georgiou, I. Y.; Miner, M. D.

2016-12-01

On river deltas dominated by proximal sediment accumulation (Mississippi, Huang He, others), the delta front region is commonly dominated by rapid accumulation of cohesive fluvial sediments, and mass-wasting processes that remobilize recently deposited sediments. Mass transport is preconditioned in sediments by high water content, biogenic gas production, over steepening, and is commonly triggered by strong wave loading and other processes. This understanding is based on extensive field studies in the 1970's and 80's. Recent studies of the Mississippi River Delta Front are yielding new perspectives on these processes, in a time of anthropogenically reduced sediment loads, rising sea level, and catastrophic deltaic land loss. We have synthesized many industry data sets collected since ca. 1980, and conducted new pilot field and modeling studies of sedimentary and morphodynamic processes. These efforts have yielded several key findings that diverge from historical understanding of this dynamic setting. First, delta distributary mouths have ceased seaward progradation, ending patterns that have been documented since the 18th century. Second, despite reduced sediment supply, offshore mass transport continues, yielding vertical displacements at rates of 1 m/y. This displacement is apparently forced by wave loading from storm events of near-annual return period, rather than major hurricanes that have been the focus of most previous studies. Third, core analysis indicates that this vertical displacement is occurring along failure planes >3 m in the seabed, rather than in more recently deposited sediments closer to the sediment-water interface. These seabed morphodynamics have the potential to destabilize both nearshore navigation infrastructure, and seabed hydrocarbon infrastructure offshore. As well, these findings raise more questions regarding the future seabed evolution offshore of major river deltas, in response to anthropogenic and climatic forcing.

Impact of rehabilitation of Assiut barrage, Nile River, on groundwater rise in urban areas

NASA Astrophysics Data System (ADS)

Dawoud, Mohamed A.; El Arabi, Nahed E.; Khater, Ahmed R.; van Wonderen, Jan

2006-08-01

To make optimum use of the most vital natural resource of Egypt, the River Nile water, a number of regulating structures (in the form of dams and barrages) for control and diversion of the river flow have been constructed in this river since the start of the 20th century. One of these barrages is the Assiut barrage which will require considerable repairs in the near future. The design of the rehabilitation of the barrage includes a headpond with water levels maintained at a level approximately 0.60 m higher than the highest water level in the headpond of the present barrage. This development will cause an increase of the seepage flow from the river towards the adjacent agricultural lands, Assiut Town and villages. The increased head pond level might cause a rise of the groundwater levels and impedance of drainage outflows. The drainage conditions may therefore be adversely affected in the so-called impacted areas which comprise floodplains on both sides of the Nile for about 70 km upstream of the future barrage. A rise in the groundwater table, particularly when high river levels impede drainage, may result in waterlogging and secondary salinization of the soil profile in agricultural areas and increase of groundwater into cellars beneath buildings in the urban areas. In addition, a rise in the groundwater table could have negative impact on existing sanitation facilities, in particular in the areas which are served with septic tanks. The impacts of increasing the headpond level were assessed using a three-dimensional groundwater model. The mechanisms of interactions between the Nile River and the underlying Quaternary aquifer system as they affect the recharge/discharge processes are comprehensively outlined. The model has been calibrated for steady state and transient conditions against historical data from observation wells. The mitigation measures for the groundwater rise in the urban areas have been tested using the calibrated mode.

A global analysis of human habitation on river deltas

NASA Astrophysics Data System (ADS)

Edmonds, Douglas; Caldwell, Rebecca; Baumgardner, Sarah; Paola, Chris; Roy, Samapriya; Nelson, Amelia; Nienhuis, Jaap

2017-04-01

River deltas are ideal sites for human habitation because of their fertile floodplains, easy access to the ocean, and abundant land. But anthropogenic and natural processes are causing deltas to sink, which increases the probability of coastal flooding and human exposure to risk. The full extent of the risk posed to humans is unclear because the number of people living on river deltas is unknown. Towards this end we mapped the locations and areas of all deltas in the world (n= 1813). Using Google Earth we identified all river mouths (≥ 50 m wide) on marine coastlines that are also connected to an upstream catchment. Rivers that split into two or more active or relict distributary channels, end in a depositional protrusion from the shoreline, or do both, are defined as deltas. The depositional protrusion and distributary channel network define the geomorphic area of each delta. We mark the position of the delta apex at the first bifurcation, or for a single channel delta at the intersection of the regional shoreline and the main channel. We mark three lateral extents, one on either side of the main channel at the maximum displacement of the depositional protrusion or the distributary network, and one on the most basinward position of the delta. We define delta area as the convex hull around these extent points and the delta apex. For each delta area polygon we extract elevation from the Shuttle Radar Topography Mission dataset and population count in years 2000, 2005, 2010, 2015, and 2020 from Gridded Population of the World, version 4. In total, deltas cover 0.56% of the total area of the world yet contain 4.1% of the world's population. The population on deltas has grown from 237 million in 2000 to projected values of 322 million in 2020. Deltaic population is growing at 1.59% per year, which outpaces the world growth rate of 1.11%. Additionally, population density is increasing with time from 322 people per km2 in year 2000 to projected values of 422 people per

Incentive compatibility and conflict resolution in international river basins: A case study of the Nile Basin

NASA Astrophysics Data System (ADS)

Wu, Xun; Whittington, Dale

2006-02-01

Nation-states rarely go to war over water, but it is equally rare that water conflicts in an international river basin are resolved through cooperation among the riparian countries that use the shared resources. Gains from cooperation will mean little to individual riparians unless the required cooperative behaviors are incentive compatible. Cooperative game theory offers useful insights for assessing cooperative solutions for water conflicts in international river basins. Applying cooperative game theory concepts such as core, nucleolus, and Shapley value to Nile water conflicts, we examine the incentive structure of both cooperative and noncooperative strategies for different riparian countries and establish some baseline conditions for incentive-compatible cooperation in the Nile basin.

Oscillatory modes of extended Nile River records (A.D. 622-1922)

NASA Astrophysics Data System (ADS)

Kondrashov, D.; Feliks, Y.; Ghil, M.

2005-05-01

The historical records of the low- and high-water levels of the Nile River are among the longest climatic records that have near-annual resolution. There are few gaps in the first part of the records (A.D. 622-1470) and larger gaps later (A.D. 1471-1922). We apply advanced spectral methods, Singular-Spectrum Analysis (SSA) and the Multi-Taper Method (MTM), to fill the gaps and to locate interannual and interdecadal periodicities. The gap filling uses a novel, iterative version of SSA. Our analysis reveals several statistically significant features of the records: a nonlinear, data-adaptive trend that includes a 256-year cycle, a quasi-quadriennial (4.2-year) and a quasi-biennial (2.2-year) mode, as well as additional periodicities of 64, 19, 12, and, most strikingly, 7 years. The quasi-quadriennial and quasi-biennial modes support the long-established connection between the Nile River discharge and the El-Niño/Southern Oscillation (ENSO) phenomenon in the Indo-Pacific Ocean. The longest periods might be of astronomical origin. The 7-year periodicity, possibly related to the biblical cycle of lean and fat years, seems to be due to North Atlantic influences.

River salinity on a mega-delta, an unstructured grid model approach.

NASA Astrophysics Data System (ADS)

Bricheno, Lucy; Saiful Islam, Akm; Wolf, Judith

2014-05-01

With an average freshwater discharge of around 40,000 m3/s the BGM (Brahmaputra Ganges and Meghna) river system has the third largest discharge worldwide. The BGM river delta is a low-lying fertile area covering over 100,000 km2 mainly in India and Bangladesh. Approximately two-thirds of the Bangladesh people work in agriculture and these local livelihoods depend on freshwater sources directly linked to river salinity. The finite volume coastal ocean model (FVCOM) has been applied to the BGM delta in order to simulate river salinity under present and future climate conditions. Forced by a combination of regional climate model predictions, and a basin-wide river catchment model, the 3D baroclinic delta model can determine river salinity under the current climate, and make predictions for future wet and dry years. The river salinity demonstrates a strong seasonal and tidal cycle, making it important for the model to be able to capture a wide range of timescales. The unstructured mesh approach used in FVCOM is required to properly represent the delta's structure; a complex network of interconnected river channels. The model extends 250 km inland in order to capture the full extent of the tidal influence and grid resolutions of 10s of metres are required to represent narrow inland river channels. The use of FVCOM to simulate flows so far inland is a novel challenge, which also requires knowledge of the shape and cross-section of the river channels.

Remote sensing, planform, and facies analysis of the Plain of Tineh, Egypt for the remains of the defunct Pelusiac River

NASA Astrophysics Data System (ADS)

Quintanar, Jessica; Khan, Shuhab D.; Fathy, Mohamed S.; Zalat, Abdel-Fattah A.

2013-11-01

The Pelusiac Branch was a distributary river in the Nile Delta that splits off from the main trunk of the Nile River as it flowed toward the Mediterranean. At approximately 25 A.D., it was chocked by sand and silt deposits from prograding beach accretion processes. The lower course of the river and its bifurcation point from the trunk of the Nile have been hypothesized based on ancient texts and maps, as well as previous research, but results have been inconsistent. Previous studies partly mapped the lower course of the Pelusiac River in the Plain of Tineh, east of the Suez Canal, but rapid urbanization related to the inauguration of the Peace Canal mega-irrigation project has covered any trace of the linear feature reported by these previous studies. The present study used multispectral remote sensing data of GeoEYE-1 and Landsat-TM to locate and accurately map the course of the defunct Pelusiac River within the Plain of Tineh. Remote sensing analysis identified a linear feature that is 135 m wide at its maximum and approximately 13 km long. It extends from the Pelusium ruins to the Suez Canal, just north of the Peace Canal. This remotely located linear feature corresponds to the path of the Pelusiac River during Roman times. Planform geomorphology was applied to determine the hydrological regime and paleodischarge of the river prior to becoming defunct. Planform analysis derived a bankfull paleodischarge value of ~ 5700 m3 s- 1 and an average discharge of 650 m3 s- 1, using the reach average for the interpreted Pelusiac River. The derived values show a river distributary similar in discharge to the modern dammed Damietta river. Field work completed in April of 2012 derived four sedimentary lithofacies of the upper formation on the plain that included pro-delta, delta-front and delta-plain depositional environments. Diatom and fossil mollusk samples were also identified that support coastal beach and lagoonal environments of deposition. Measured section columns

Impacts of seawater rise on seawater intrusion in the Nile Delta Aquifer, Egypt.

PubMed

Sefelnasr, Ahmed; Sherif, Mohsen

2014-01-01

Several investigations have recently considered the possible impacts of climate change and seawater level rise on seawater intrusion in coastal aquifers. All have revealed the severity of the problem and the significance of the landward movement of the dispersion zone under the condition of seawater level rise. Most of the studies did not consider the possible effects of the seawater rise on the inland movement of the shoreline and the associate changes in the boundary conditions at the seaside and the domain geometry. Such effects become more evident in flat, low land, coastal alluvial plans where large areas might be submerged with seawater under a relatively small increase in the seawater level. None of the studies combined the effect of increased groundwater pumping, due to the possible decline in precipitation and shortage in surface water resources, with the expected landward shift of the shore line. In this article, the possible effects of seawater level rise in the Mediterranean Sea on the seawater intrusion problem in the Nile Delta Aquifer are investigated using FEFLOW. The simulations are conducted in horizontal view while considering the effect of the shoreline landward shift using digital elevation models. In addition to the basic run (current conditions), six different scenarios are considered. Scenarios one, two, and three assume a 0.5 m seawater rise while the total pumping is reduced by 50%, maintained as per the current conditions and doubled, respectively. Scenarios four, five, and six assume a 1.0 m seawater rise and the total pumping is changed as in the first three scenarios. The shoreline is moved to account for the seawater rise and hence the study domain and the seaside boundary are modified accordingly. It is concluded that, large areas in the coastal zone of the Nile Delta will be submerged by seawater and the coast line will shift landward by several kilometers in the eastern and western sides of the Delta. Scenario six represents

Effect of tides, river flow, and gate operations on entrainment of juvenile salmon into the interior Sacramento–San Joaquin River Delta

USGS Publications Warehouse

Perry, Russell W.; Brandes, Patricia L.; Burau, Jon R.; Sandstrom, Philip T.; Skalski, John R.

2015-01-01

Juvenile Chinook Salmon Oncorhynchus tshawytscha emigrating from natal tributaries of the Sacramento River, California, must negotiate the Sacramento-San Joaquin River Delta (hereafter, the Delta), a complex network of natural and man-made channels linking the Sacramento River with San Francisco Bay. Fish that enter the interior and southern Delta—the region to the south of the Sacramento River where water pumping stations are located—survive at a lower rate than fish that use alternative migration routes. Consequently, total survival decreases as the fraction of the population entering the interior Delta increases, thus spurring management actions to reduce the proportion of fish that are entrained into the interior Delta. To better inform management actions, we modeled entrainment probability as a function of hydrodynamic variables. We fitted alternative entrainment models to telemetry data that identified when tagged fish in the Sacramento River entered two river channels leading to the interior Delta (Georgiana Slough and the gated Delta Cross Channel). We found that the probability of entrainment into the interior Delta through both channels depended strongly on the river flow and tidal stage at the time of fish arrival at the river junction. Fish that arrived during ebb tides had a low entrainment probability, whereas fish that arrived during flood tides (i.e., when the river's flow was reversed) had a high probability of entering the interior Delta. We coupled our entrainment model with a flow simulation model to evaluate the effect of nighttime closures of the Delta Cross Channel gates on the daily probability of fish entrainment into the interior Delta. Relative to 24-h gate closures, nighttime closures increased daily entrainment probability by 3 percentage points on average if fish arrived at the river junction uniformly throughout the day and by only 1.3 percentage points if 85% of fish arrived at night. We illustrate how our model can be used to

21,000 years of Ethiopian African monsoon variability recorded in sediments of the western Nile deep-sea fan: impact of the Nile freshwater inflow for the Mediterranean thermo-haline circulation

NASA Astrophysics Data System (ADS)

Revel, Marie; Colin, Christophe; Bernasconi, Stephano; Combourieu-Nebout, Nathalie; Ducassou, Emmanuelle; Rolland, Yann; Bosch, Delphine

2014-05-01

The Nile delta sedimentation constitutes a continuous high resolution (1.6 mm/year) record of Ethiopian African monsoon regime intensity. Multiproxy analyses performed on core MS27PT recovered in hemipelagic Nile sediment margin (<90 km outward of the Rosetta mouth of the Nile) allow the quantification of the Saharan aeolian dust and the Blue/White Nile River suspended matter frequency fluctuations during the last 21 cal. ka BP. The radiogenic Sr and Nd isotopes, clay mineralogy, bulk elemental composition and palynological analyses reveal large changes in source components, oscillating between a dominant aeolian Saharan contribution during the LGM and the Late Holocene (~4 to 2 cal. ka BP), a dominant Blue/Atbara Nile River contribution during the early Holocene (15 to 8.4 cal. ka BP) and a probable White Nile River contribution during the Middle Holocene (8.4 to 4 cal. ka BP). The following main features are highlighted: 1. The rapid shift from the LGM arid conditions to the African Humid Period (AHP) started at about 15 cal. ka BP. AHP extends until 8.4 cal. ka BP, and we suggest that the Ethiopian African Monsoon maximum between 12 and 8 cal. ka BP is responsible for a larger Blue/Atbara Nile sediment load and freshwater input into the Eastern Mediterranean Sea. 2. The transition between the AHP and the arid Late Holocene is gradual and occurs in two main phases between 8.4 and 6.5 cal. ka BP and 6.5 to 3.2 cal. ka BP. We suggest that the main rain belt shifted southward from 8.4 to ~4 cal. ka BP and was responsible for progressively reduced sediment load and freshwater input into the eastern Mediterranean Sea. 3. The aridification along the Nile catchments occurred from ~4 to 2 cal. ka BP. A dry period, which culminates at 3.2 cal. ka BP, and seems to coincide with a re-establishment of increased oceanic primary productivity in the western Mediterranean Sea. We postulate that the decrease in thermo-haline water Mediterranean circulation could be part of a

An approach for delineating drinking water wellhead protection areas at the Nile Delta, Egypt.

PubMed

Fadlelmawla, Amr A; Dawoud, Mohamed A

2006-04-01

In Egypt, production has a high priority. To this end protecting the quality of the groundwater, specifically when used for drinking water, and delineating protection areas around the drinking water wellheads for strict landuse restrictions is essential. The delineation methods are numerous; nonetheless, the uniqueness of the hydrogeological, institutional as well as social conditions in the Nile Delta region dictate a customized approach. The analysis of the hydrological conditions and land ownership at the Nile Delta indicates the need for an accurate methodology. On the other hand, attempting to calculate the wellhead protected areas around each of the drinking wells (more than 1500) requires data, human resources, and time that exceed the capabilities of the groundwater management agency. Accordingly, a combination of two methods (simplified variable shapes and numerical modeling) was adopted. Sensitivity analyses carried out using hypothetical modeling conditions have identified the pumping rate, clay thickness, hydraulic gradient, vertical conductivity of the clay, and the hydraulic conductivity as the most significant parameters in determining the dimensions of the wellhead protection areas (WHPAs). Tables of sets of WHPAs dimensions were calculated using synthetic modeling conditions representing the most common ranges of the significant parameters. Specific WHPA dimensions can be calculated by interpolation, utilizing the produced tables along with the operational and hydrogeological conditions for the well under consideration. In order to simplify the interpolation of the appropriate dimensions of the WHPAs from the calculated tables, an interactive computer program was written. The program accepts the real time data of the significant parameters as its input, and gives the appropriate WHPAs dimensions as its output.

Entropy and optimality in river deltas

NASA Astrophysics Data System (ADS)

Tejedor, Alejandro; Longjas, Anthony; Edmonds, Douglas A.; Zaliapin, Ilya; Georgiou, Tryphon T.; Rinaldo, Andrea; Foufoula-Georgiou, Efi

2017-10-01

The form and function of river deltas is intricately linked to the evolving structure of their channel networks, which controls how effectively deltas are nourished with sediments and nutrients. Understanding the coevolution of deltaic channels and their flux organization is crucial for guiding maintenance strategies of these highly stressed systems from a range of anthropogenic activities. To date, however, a unified theory explaining how deltas self-organize to distribute water and sediment up to the shoreline remains elusive. Here, we provide evidence for an optimality principle underlying the self-organized partition of fluxes in delta channel networks. By introducing a suitable nonlocal entropy rate (nER) and by analyzing field and simulated deltas, we suggest that delta networks achieve configurations that maximize the diversity of water and sediment flux delivery to the shoreline. We thus suggest that prograding deltas attain dynamically accessible optima of flux distributions on their channel network topologies, thus effectively decoupling evolutionary time scales of geomorphology and hydrology. When interpreted in terms of delta resilience, high nER configurations reflect an increased ability to withstand perturbations. However, the distributive mechanism responsible for both diversifying flux delivery to the shoreline and dampening possible perturbations might lead to catastrophic events when those perturbations exceed certain intensity thresholds.

Carbon storage in the Mississippi River delta enhanced by environmental engineering

NASA Astrophysics Data System (ADS)

Shields, Michael R.; Bianchi, Thomas S.; Mohrig, David; Hutchings, Jack A.; Kenney, William F.; Kolker, Alexander S.; Curtis, Jason H.

2017-11-01

River deltas have contributed to atmospheric carbon regulation throughout Earth history, but functioning in the modern era has been impaired by reduced sediment loads, altered hydrologic regimes, increased global sea-level rise and accelerated subsidence. Delta restoration involves environmental engineering via river diversions, which utilize self-organizing processes to create prograding deltas. Here we analyse sediment cores from Wax Lake delta, a product of environmental engineering, to quantify the burial of organic carbon. We find that, despite relatively low concentrations of organic carbon measured in the cores (about 0.4%), the accumulation of about 3 T m-2 of sediment over the approximate 60 years of delta building resulted in the burial of a significant amount of organic carbon (16 kg m-2). This equates to an apparent organic carbon accumulation rate of 250 +/- 23 g m-2 yr-1, which implicitly includes losses by carbon emissions and erosion. Our estimated accumulation rate for Wax Lake delta is substantially greater than previous estimates based on the top metre of delta sediments and comparable to those of coastal mangrove and marsh habitats. The sedimentation of carbon at the Wax Lake delta demonstrates the capacity of engineered river diversions to enhance both coastal accretion and carbon burial.

Redox-induced mobilization of copper, selenium, and zinc in deltaic soils originating from Mississippi (U.S.A.) and Nile (Egypt) River Deltas: A better understanding of biogeochemical processes for safe environmental management.

PubMed

Shaheen, Sabry M; Frohne, Tina; White, John R; DeLaune, Ron D; Rinklebe, Jörg

2017-01-15

Studies about the mobilization of potentially toxic elements (PTEs) in deltaic soils can be challenging, provide critical information on assessing the potential risk and fate of these elements and for sustainable management of these soils. The impact of redox potential (E H ), pH, iron (Fe), manganese (Mn), sulfate (SO 4 2- ), chloride (Cl - ), aliphatic dissolved organic carbon (DOC), and aromatic dissolved organic carbon (DAC) on the mobilization of copper (Cu), selenium (Se), and zinc (Zn) was studied in two soils collected from the Nile and Mississippi Rivers deltaic plains focused on increasing our understanding of the fate of these toxic elements. Soils were exposed to a range of redox conditions stepwise from reducing to oxidizing soil conditions using an automated biogeochemical microcosm apparatus. Concentrations of DOC and Fe were high under reducing conditions as compared to oxidizing conditions in both soils. The proportion of DAC in relation to DOC in solution (aromaticity) was high in the Nile Delta soil (NDS) and low in the Mississippi Delta soil (MDS) under oxidizing conditions. Mobilization of Cu was low under reducing conditions in both soils which was likely caused by sulfide precipitation and as a result of reduction of Cu 2+ to Cu 1+ . Mobilization of Se was high under low E H in both soils. Release of Se was positively correlated with DOC, Fe, Mn, and SO 4 2- in the NDS, and with Fe in the MDS. Mobilization of Zn showed negative correlations with E H and pH in the NDS while these correlations were non-significant in the MDS. The release dynamics of dissolved Zn could be governed mainly by the chemistry of Fe and Mn in the NDS and by the chemistry of Mn in the MDS. Our findings suggest that a release of Se and Zn occurs under anaerobic conditions, while aerobic conditions favor the release of Cu in both soils. In conclusion, the release of Cu, Se, and Zn under different reducing and oxidizing conditions in deltaic wetland soils should be taken

Sediment and water chemistry of the San Juan River and Escalante River deltas of Lake Powell, Utah, 2010-2011

USGS Publications Warehouse

Hornewer, Nancy J.

2014-01-01

Recent studies have documented the presence of trace elements, organic compounds including polycyclic aromatic hydrocarbons, and radionuclides in sediment from the Colorado River delta and from sediment in some side canyons in Lake Powell, Utah and Arizona. The fate of many of these contaminants is of significant concern to the resource managers of the National Park Service Glen Canyon National Recreation Area because of potential health impacts to humans and aquatic and terrestrial species. In 2010, the U.S. Geological Survey began a sediment-core sampling and analysis program in the San Juan River and Escalante River deltas in Lake Powell, Utah, to help the National Park Service further document the presence or absence of contaminants in deltaic sediment. Three sediment cores were collected from the San Juan River delta in August 2010 and three sediment cores and an additional replicate core were collected from the Escalante River delta in September 2011. Sediment from the cores was subsampled and composited for analysis of major and trace elements. Fifty-five major and trace elements were analyzed in 116 subsamples and 7 composited samples for the San Juan River delta cores, and in 75 subsamples and 9 composited samples for the Escalante River delta cores. Six composited sediment samples from the San Juan River delta cores and eight from the Escalante River delta cores also were analyzed for 55 low-level organochlorine pesticides and polychlorinated biphenyls, 61 polycyclic aromatic hydrocarbon compounds, gross alpha and gross beta radionuclides, and sediment-particle size. Additionally, water samples were collected from the sediment-water interface overlying each of the three cores collected from the San Juan River and Escalante River deltas. Each water sample was analyzed for 57 major and trace elements. Most of the major and trace elements analyzed were detected at concentrations greater than reporting levels for the sediment-core subsamples and composited

A Regional Survey of River-plume Sedimentation on the Mississippi River Delta Front

NASA Astrophysics Data System (ADS)

Courtois, A. J.; Bentley, S. J.; Xu, K.; Georgiou, I. Y.; Maloney, J. M.; Miner, M. D.; Chaytor, J. D.; Smith, J.

2017-12-01

Many studies of the Mississippi River and Delta (MRD) have shown historic declines in sediment load reaching the main river distributaries over the last few decades. Recent studies also reported that 50% of the suspended load during floods is sequestered within the delta. While the impact of declining sediment load on wetland loss is well documented, submarine sedimentary processes on the delta front during this recent period of declining sediment load are understudied. To better understand modern sediment dispersal and deposition across the Mississippi River Delta Front, 31 multicores were collected in June 2017 from locations extending offshore from Southwest Pass, South Pass, and Pass a Loutre (the main river outlets) in water depths of 25-280 m. Core locations were selected based on multibeam bathymetry and morphology collected by the USGS in May 2017; the timing of collection coincided with the end of annual peak discharge on the Mississippi River. This multi-agency survey is the first to study delta-front sedimentary processes regionally with such a wide suite of tools. Target locations for coring included the dominant depositional environments: mudflow lobes, gullies, and undisturbed prodelta. Cores were subsampled at 2 cm intervals and analyzed for Beryllium-7 activity via gamma spectrometry; in such settings, Be-7 can be used as a tracer of sediment recently delivered from fluvial origin. Results indicate a general trend of declining Be-7 activity with increasing distance from source, and in deeper water. Inshore samples near Southwest Pass show the deepest penetration depth of Be-7 into the sediment (24-26 cm), which is a preliminary indicator of rapid seasonal sedimentation. Nearshore samples from South Pass exhibited similar Be-7 penetration depths, with results near Pass a Loutre to 14-16 cm depth. Be-7 remains detectable to 2 cm in water 206 m deep, approximately 20 km from South Pass. Sediment dispersal remains impressive offshore from all three

Linking rapid erosion of the Mekong River delta to human activities.

PubMed

Anthony, Edward J; Brunier, Guillaume; Besset, Manon; Goichot, Marc; Dussouillez, Philippe; Nguyen, Van Lap

2015-10-08

As international concern for the survival of deltas grows, the Mekong River delta, the world's third largest delta, densely populated, considered as Southeast Asia's most important food basket, and rich in biodiversity at the world scale, is also increasingly affected by human activities and exposed to subsidence and coastal erosion. Several dams have been constructed upstream of the delta and many more are now planned. We quantify from high-resolution SPOT 5 satellite images large-scale shoreline erosion and land loss between 2003 and 2012 that now affect over 50% of the once strongly advancing >600 km-long delta shoreline. Erosion, with no identified change in the river's discharge and in wave and wind conditions over this recent period, is consistent with: (1) a reported significant decrease in coastal surface suspended sediment from the Mekong that may be linked to dam retention of its sediment, (2) large-scale commercial sand mining in the river and delta channels, and (3) subsidence due to groundwater extraction. Shoreline erosion is already responsible for displacement of coastal populations. It is an additional hazard to the integrity of this Asian mega delta now considered particularly vulnerable to accelerated subsidence and sea-level rise, and will be exacerbated by future hydropower dams.

Natural and Human Impacts on Recent Development of Asian Large Rivers and Deltas

NASA Astrophysics Data System (ADS)

Liu, P.; Lu, C.

2014-12-01

Most recent data analysis indicates sediment loads in most of Asian large rivers (like, Yellow, Yangtze, Pearl, Chao Phraya, Indus, Krishna, Godavari, etc) have decreased up to 80-90% in the past 60 years. Correspondingly, most of Asian large river deltas are facing severe sediment starving; delta shoreline comparisons indicate that some are under strong coastal erosion. For examples, the Yellow River Delta has been retreating since 1990s when its annual sediment load has kept below 300 million tons. The Yangtze River delta kept growing before Three Gorges Dams was operating, and began to be eroded from the year 2003 to 2009, and then prograded locally due to the Deep Water Navigation Project. The Mekong Delta shoreline has also been dynamically changing with the sediment flux variation, eroding from 1989 to 1996 and prograding from 1996 to 2002. More information is available at http://www.meas.ncsu.edu/sealevel

[Distribution and sources of polycyclic aromatic hydrocarbons in sediments from rivers of Pearl River Delta and its nearby South China Sea].

PubMed

Luo, Xiao-Jun; Chen, She-Jun; Mai, Bi-Xian; Zeng, Yong-Ping; Sheng, Guo-Ying; Fu, Jia-Mo

2005-07-01

Polycyclic aromatic hydrocarbons (PAHs) are measured in surface sediments from rivers and estuary of Pearl River Delta and its nearby South China Sea. Total PAH concentration varied from 255.9 - 16 670.3 ng/g and a moderate to low level compare to relevant areas worldwide. The order of PAHs concentration in sediments was: rivers of Pearl River Delta > estuary > South China Sea, and the most significant PAH contamination was at Guangzhou channel of Zhujiang river. A decrease trend for PAHs concentration with distance from estuary to open sea can be sees in South China Sea. Coal and biomass combustion is the major source of PAHs in nearshore of South China Sea, and petroleum combustion is the main source of pyrolytic PAHs in rivers and estuary of Pearl River Delta according to PAHs diagnostic ratios. Petroleum PAHs are revealed have a high contribution to PAHs in Xijiang River, estuary and some stations in Zhujiang River. A comparison of data from study in 1997 with data from present study indicates that there is no clear change in the PAH concentration over time but the source of PAHs in Pearl River Delta have been change from a main coal combustion to petroleum combustion and being reflect in the sediments in rivers and estuary of Pearl River Delta where there have high sedimentation rate.

Coastline change and marine geo-hazards in the Yellow River Delta (China)

NASA Astrophysics Data System (ADS)

Zhou, L.; Liu, J.; Liu, X.

2003-04-01

COASTLINE CHANGE AND MARINE GEO-HAZARDS IN THE YELLOW RIVER DELTA (CHINA) Zhou Liangyong(1,2), Liu Jian(1,3), Liu Xiqing(1) (1)Qingdao Institute of Marine Geology,(2)Ocean University of China,(3)Research Centre for Coastal Geology, CGS qdzliangyong@cgs.gov.cn/Fax: +86-532-5720553 Satellite remote sensing, bathymetry and high-resolution seismic data have been used to examine the coastline change during the period from 1976 to 2001 and the offshore marine geo-hazards in the modern Yellow River Delta. Trends in the temporal sequence of the eight coastlines derived from Landsat images were used in the definition of erosional classes of the coastline. Four classes were distinguished, including rapid erosion (>100 m/yr), moderate erosion (20-100 m/yr), no detectable erosion (-1 - 20 m/yr), and accretion (-200--1 m/yr). We revealed the subtle variations in sea floor morphology and sediment geometries using high-resolution acoustic survey. Many kinds of geo-hazards were identified in the active subaqueous delta lobe and abandoned delta lobes, such as seabed erosions, gas-charged sediments, listric faults, synsedimentary rises, incised palaeo-valleys, infilled gullies, diapirs, active slope failures and sediment collapses. The resultant map of geo-envrionment and geo-hazards presents the coastline change and distribution of geo-hazards mentioned above in the Yellow River Delta. The gas-charged sediment distributes mainly in the abandoned delta lobes. The synsedimentary rise outside of the modern river mouth is a new evidence for the seabed mass-movement which modifies the progradational subaquaeous slopes of modern Yellow River Delta.

Impacts of the Indian Rivers Inter-link Project on Sediment Transport to River Deltas

NASA Astrophysics Data System (ADS)

Higgins, S.; Overeem, I.; Syvitski, J. P.

2015-12-01

The Indian Rivers Inter-link project is a proposal by the Indian government to link several of India's major rivers via a network of reservoirs and canals. Variations of the IRI have been discussed since 1980, but the current plan has recently received increased support from the Indian government. Construction on three canals has controversially begun. If the Inter-link project moves forward, fourteen canals will divert water from tributaries of the Ganges and Brahmaputra rivers to areas in the west, where fresh water is needed for irrigation. Additional canals would transport Himalayan sediments 500 km south to the Mahanadi delta and more than 1000 km south to the Godavari and Krishna deltas. We investigate the impacts of the proposed diversions on sediment transport to the Mahanadi/Brahmani, Godavari, and Krishna deltas in India and the Ganges-Brahmaputra Delta in Bangladesh. We map the entire river network and the proposed new nodes and connections. Changing watersheds are delineated using the Terrain Analysis Using Digital Elevation Models (TauDEM) Suite. Climate data comes from interpolation between observed precipitation stations located in China, Nepal, India, Bhutan and Bangladesh. Changes in water discharge due to the proposed canals are simulated using HydroTrend, a climate-driven hydrological water balance and transport model that incorporates drainage area, discharge, relief, temperature, basin-average lithology, and anthropogenic influences. Simulated river discharge is validated against observations from gauging stations archived by the Global Runoff Data Center (GRDC). HydroTrend is then used to investigate sediment transport changes that may result from the proposed canals. We also quantify changes in contributing areas for the outlets of nine major Indian rivers, showing that more than 50% of the land in India will contribute a portion of its runoff to a new outlet should the entire canal system be constructed.

Sedimentary Facies and Stratigraphy of the Changjiang (Yangtze River) Delta

NASA Astrophysics Data System (ADS)

Dalrymple, R. W.; Zhang, X.; Lin, C. M.

2017-12-01

A disproportionate number of the world's largest deltas are tide-dominated or strongly tide-influenced, in part because the low gradient of these rivers allows the tide to penetrate far inland, generating strong tidal currents at the river mouth. These deltas also tend to be mud-dominated because a significant fraction of the bedload is trapped farther inland. Despite their great importance as sediment depo-centers, as analogues for ancient sedimentary successions, and as areas of intense human occupation, they are the most poorly understood coastal system. The Changjiang (Yangtze River), the 4th largest river in the world in terms of sediment discharge, is one such tide-dominated system, with a mean tidal range of 2.7 m and tidal-current speeds of 1 m/s at its mouth. It shows a fairly typical series of low-relief channels and bars in the mouth-bar area and passes seaward and down-drift into a coastal mud belt that extends 800 km to the south of the river mouth. The deposits from both the transgressive-phase and modern delta are all dominated by mud, except for the fluvial-channel deposits that are clean sand. Channel-floor deposits in areas with appreciable tidal influence contain abundant fluid-mud layers (1-3 cm thick), intercalated with relatively coarse sand; such mud layers show evidence of tidal cyclicity. The overlying tidal-bar deposits commonly become sandier upward because of the upward loss of fluid-mud layers. The tidal channels and bars that characterize the mouth-bar and delta-front area are dominated by randomly organized structureless mud layers, 5-30 cm thick, that are interpreted to be storm-generated fluid-mud deposits. These mud layers become less abundant upward, generating upward-sanding successions. These facies are very similar to those seen in the Amazon and Fly River deltas, suggesting that this is a common motif, and indicating the importance of fluid mud in the dynamics of such systems. Facies proximality can be determined by careful

Is there a self-organization principle of river deltas?

NASA Astrophysics Data System (ADS)

Tejedor, Alejandro; Longjas, Anthony; Foufoula-Georgiou, Efi

2017-04-01

River deltas are known to possess a complex topological and flux-partitioning structure which has recently been quantified using spectral graph theory [Tejedor et al., 2015a,b]. By analysis of real and simulated deltas it has also been shown that there is promise in formalizing relationships between this topo-dynamic delta structure and the underlying delta forming processes [e.g., Tejedor et al., 2016]. The question we pose here is whether there exists a first order organizational principle behind the self-organization of river deltas and whether this principle can be unraveled from the co-evolving topo-dynamic structure encoded in the delta planform. To answer this question, we introduce a new metric, the nonlocal Entropy Rate (nER) that captures the information content of a delta network in terms of the degree of uncertainty in delivering fluxes from any point of the network to the shoreline. We hypothesize that if the "guiding principle" of undisturbed deltas is to efficiently and robustly build land by increasing the diversity of their flux pathways over the delta plane, then they would exhibit maximum nonlocal Entropy Rate at states at which geometry and flux dynamics are at equilibrium. At the same time, their nER would be non-optimal at transient states, such as before and after major avulsions during which topology and dynamics adjust to each other to reach a new equilibrium state. We will present our results for field and simulated deltas, which confirm this hypothesis and open up new ways of thinking about self-organization, complexity and robustness in river deltas. One particular connection of interest might have important implications since entropy rate and resilience are related by the fluctuation theorem [Demetrius and Manke, 2005], and therefore our results suggest that deltas might in fact self-organize to maximize their resilience to structural and dynamic perturbations. References: Tejedor, A., A. Longjas, I. Zaliapin, and E. Foufoula

Variability Matters: New Insights into Mechanics of River Avulsions on Deltas and Their Deposits

NASA Astrophysics Data System (ADS)

Ganti, V.

2015-12-01

River deltas are highly dynamic, often fan-shaped depositional systems that form when rivers drain into a standing body of water. They host over a half billion people and are currently under threat of drowning and destruction by relative sea-level rise, subsidence, and anthropogenic interference. Deltas often develop planform fan shapes through avulsions, whereby major river channel shifts occur via "channel jumping" about a spatial node, thus determining their fundamental length scale. Emerging theories suggest that the size of delta lobes is set by backwater hydrodynamics; however, these ideas are difficult to test on natural deltas, which evolve on centennial to millennial timescales. In this presentation, I will show results from the first laboratory delta built through successive deposition of lobes that maintain a constant size that scales with backwater hydrodynamics. The characteristic size of deltas emerges because of a preferential avulsion node that remains fixed spatially relative to the prograding shoreline, and is a consequence of multiple river floods that produce persistent morphodynamic river-bed adjustment within the backwater zone. Moreover, river floods cause erosion in the lowermost reaches of the alluvial river near their coastline, which may leave erosional boundaries in the sedimentary record that may appear similar to those previously interpreted to be a result of relative sea-level fall. I will discuss the implications of these findings in the context of sustainability management of deltas, decoding their stratigraphic record, and identifying ancient standing bodies of water on other planets such as Mars. Finally, I will place this delta study in a broader context of recent work that highlights the importance of understanding and quantifying variability in sedimentology and geomorphology.

What Role do Hurricanes Play in Sediment Delivery to Subsiding River Deltas?

NASA Astrophysics Data System (ADS)

Smith, J. E., IV

2016-02-01

James E. Smith IV1, Samuel J. Bentley, Sr.1, Gregg A. Snedden2, Crawford White1 Department of Geology and Geophysics and Coastal Studies Institute, Louisiana State University, Baton Rouge, LA 70803 USA United States Geological Survey, National Wetlands Research Center, Baton Rouge LA 70803 USA The Mississippi River Delta has undergone tremendous land loss over the past century due to natural and anthropogenic influences, a fate shared by many river deltas globally. A globally unprecedented effort to restore and sustain the remaining subaerial portions of the delta is now underway, an endeavor that is expected to cost $50-100B over the next 50 yr. Success of this effort requires a thorough understanding of natural and anthropogenic controls on sediment supply, accumulation, and delta geomorphology. In the Mississippi River Delta, hurricanes have been paradoxically identified as both agents of widespread land loss, and positive influences for marsh vertical sediment accretion. We present the first multi-decadal chronostratigraphic assessment of sediment supply for a major coastal basin of the Mississippi River Delta that assesses both fluvial and hurricane-induced contributions to sediment accumulation in deltaic wetlands. Twenty seven cores have been analyzed for radioisotope geochronology and organic content to establish the chronology of mineral sediment supply to the wetlands over the past 70 years. Our findings indicate that over multidecadal timescales, hurricane-induced sediment delivery may be an important contributor for deltaic wetland vertical accretion, but the contribution from hurricanes to long-term sediment accumulation is substantially less than sediment delivery supplied by existing and planned river-sediment diversions at present-day river-sediment loads.

Mackenzie River Delta morphological change based on Landsat time series

NASA Astrophysics Data System (ADS)

Vesakoski, Jenni-Mari; Alho, Petteri; Gustafsson, David; Arheimer, Berit; Isberg, Kristina

2015-04-01

Arctic rivers are sensitive and yet quite unexplored river systems to which the climate change will impact on. Research has not focused in detail on the fluvial geomorphology of the Arctic rivers mainly due to the remoteness and wideness of the watersheds, problems with data availability and difficult accessibility. Nowadays wide collaborative spatial databases in hydrology as well as extensive remote sensing datasets over the Arctic are available and they enable improved investigation of the Arctic watersheds. Thereby, it is also important to develop and improve methods that enable detecting the fluvio-morphological processes based on the available data. Furthermore, it is essential to reconstruct and improve the understanding of the past fluvial processes in order to better understand prevailing and future fluvial processes. In this study we sum up the fluvial geomorphological change in the Mackenzie River Delta during the last ~30 years. The Mackenzie River Delta (~13 000 km2) is situated in the North Western Territories, Canada where the Mackenzie River enters to the Beaufort Sea, Arctic Ocean near the city of Inuvik. Mackenzie River Delta is lake-rich, productive ecosystem and ecologically sensitive environment. Research objective is achieved through two sub-objectives: 1) Interpretation of the deltaic river channel planform change by applying Landsat time series. 2) Definition of the variables that have impacted the most on detected changes by applying statistics and long hydrological time series derived from Arctic-HYPE model (HYdrologic Predictions for Environment) developed by Swedish Meteorological and Hydrological Institute. According to our satellite interpretation, field observations and statistical analyses, notable spatio-temporal changes have occurred in the morphology of the river channel and delta during the past 30 years. For example, the channels have been developing in braiding and sinuosity. In addition, various linkages between the studied

Heavy metal flows in aquatic systems of the Don and Kuban river deltas

NASA Astrophysics Data System (ADS)

Tkachenko, A. N.; Tkachenko, O. V.; Lychagin, M. Yu.; Kasimov, N. S.

2017-05-01

This paper presents the calculated heavy metal (Fe, Mn, Zn, Ni, Cu, Cr, Co, Cd, and Pb) flows in suspended and dissolved forms in the main navigable branches of the Don and Kuban river deltas during the low-water period of 2013-2014. This work is based on the data of field studies in which water and suspended matter samples were collected and the turbidity and water discharge in deltas were measured. A quantitative estimate of heavy metal inflows into the deltas of the Don and Kuban rivers is provided. Transformation of flows of suspended and dissolved metal forms from the delta top to the sea edge is discussed. The influence of localities (Rostov-on-Don, Temryuk) on the increase in heavy metal flows downstream is shown, and the heavy metal flows in the deltas of the Don and Kuban rivers are compared.

Seasonal extension of the Nile River plume into the Mediterranean Sea measured by its optical properties from satellite products

NASA Astrophysics Data System (ADS)

El-Mezayen, M. M.; Rueda-Roa, D. T.; Muller-Karger, F. E.; Otis, D. B.

2016-12-01

The Eastern Mediterranean is a semi-enclosed sea, considered oligotrophic except for the Levantine basin (LB) (30°-38° N, 28°-36° E) where the Nile River plays an important role in its water budget and biogeochemical properties. We studied the seasonality of the Nile River plume using ocean color satellite imagery. We analyzed 1 km resolution satellite chlorophyll-a (Chl-a) and Colored Dissolved Organic Matter (CDOM) concentration estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS, 2002-2015). We used a threshold of 0.2 mg m-3 of Chl-a and 0.03 m-1 of CDOM as a proxy to mask out and calculate the extension of the Nile plume. The plume was always constrained to the coastal region of SE Mediterranean Sea over the 13-year period examined. The annual average surface area of the Nile plume estimated with Chl-a and CDOM was similar (26,245 and 21,195 Km2, respectively). The minimum Nile plume area occurred between April and December (21,329 and 19,177 Km2, for Chl-a and CDOM respectively). Maximum area extension was observed between January-March for both Chl-a and CDOM (40,993 and 27,251 Km2, respectively). There was a conspicuous difference in the maximum surface area of the Nile plume measured with the Chl-a product during February (54,053 Km2) relative to the CDOM proxy (30,749 Km2). During January-March the area of the Nile discharge measured with Chl-a was 1.3-1.8 larger than with the CDOM product, while they were similar the rest of the year. Correlation between Chl-a and CDOM results was high during April-December (R2=0.93, n=122, p<0.001) but somewhat low during January-March (R2=0.65, n=39, p<0.001). This indicates that there is a larger phytoplankton bloom during January-March, due to higher nutrient discharge by Nile water. Both satellite proxies are good indicators of the extent of the Nile plume. We will present further research on the seasonal extension of the Nile plume along the coast and in the LB.

Elemental Analysis and Radionuclides Monitoring of Beach Black Sand at North of Nile Delta, Egypt

NASA Astrophysics Data System (ADS)

Ali, Abdallah; Fayez-Hassan, M.; Mansour, N. A.; Mubarak, Fawzia; Ahmed, Talaat Salah; Hassanin, W. F.

2017-12-01

A study was carried out on the concentrations of elements presented in beach black sand samples collected from North of Nile Delta along Mediterranean Coast using instrumental neutron activation analysis (INAA) as an effective analysis technique, especially for monitoring elements. The Egyptian Research Reactor-2 (ETRR-2) as a facility was used for the samples irradiation in the thermal mode of a neutron flux 3 × 1011 n/cm2 s. Natural radioactive elements, rare element and heavy elements as U, Th, La, Lu, Sm, Ce, Nd, Eu, Gd, Sc, Tb, Yb, As, Br, Na, Sb, Ba, Co, Cr, Fe, Hg, Hf, Sr, Ta, Zn and Zr were determined with concentrations average values 16.3, 78.8, 195.4, 3.3, 31.3, 445.1, 223, 7.2, 8.5, 97.1, 3.6, 31.1, 6.1, 24.5, 27,236.8, 1.42, 1327.7, 81.1, 1814.3, 263,735, 0.1, 237.3, 878.7, 20.8, 671.1 and 6225.9 (mg/kg), respectively. The experimental data results were analyzed to evidence any correlations of these elements as well as to know the geological formation in the study area. The elements concentrations in the black sand samples were found higher than the world average crustal soil values except for As and Sb. Results were compared with similar beach black sand in previous studies. The enrichment factor (EF) and geoaccumulation index (I geo) for heavy elements were presented to evaluate the contamination rate. We can summarize that exposure for natural radionuclides (U and Th) in this area were still within the acceptable limits due to little time of exposure. Therefore, the black sands from North of Nile Delta are not recommended for use in building constructions due to high radioactive doses.

Quantitative metrics that describe river deltas and their channel networks

NASA Astrophysics Data System (ADS)

Edmonds, Douglas A.; Paola, Chris; Hoyal, David C. J. D.; Sheets, Ben A.

2011-12-01

Densely populated river deltas are losing land at an alarming rate and to successfully restore these environments we must understand the details of their morphology. Toward this end we present a set of five metrics that describe delta morphology: (1) the fractal dimension, (2) the distribution of island sizes, (3) the nearest-edge distance, (4) a synthetic distribution of sediment fluxes at the shoreline, and (5) the nourishment area. The nearest-edge distance is the shortest distance to channelized or unchannelized water from a given location on the delta and is analogous to the inverse of drainage density in tributary networks. The nourishment area is the downstream delta area supplied by the sediment coming through a given channel cross section and is analogous to catchment area in tributary networks. As a first step, we apply these metrics to four relatively simple, fluvially dominated delta networks. For all these deltas, the average nearest-edge distances are remarkably constant moving down delta suggesting that the network organizes itself to maintain a consistent distance to the nearest channel. Nourishment area distributions can be predicted from a river mouth bar model of delta growth, and also scale with the width of the channel and with the length of the longest channel, analogous to Hack's law for drainage basins. The four delta channel networks are fractal, but power laws and scale invariance appear to be less pervasive than in tributary networks. Thus, deltas may occupy an advantageous middle ground between complete similarity and complete dissimilarity, where morphologic differences indicate different behavior.

Serological tests for detecting Rift Valley fever viral antibodies in sheep from the Nile Delta.

PubMed Central

Scott, R M; Feinsod, F M; Allam, I H; Ksiazek, T G; Peters, C J; Botros, B A; Darwish, M A

1986-01-01

To determine the accuracy of serological methods in detecting Rift Valley fever (RVF) viral antibodies, we examined serum samples obtained from 418 sheep in the Nile Delta by using five tests. The plaque reduction neutralization test (PRNT) was considered the standard serological method against which the four other tests were compared. Twenty-four serum samples had RVF viral antibodies detected by PRNT. Hemagglutination inhibition and enzyme-linked immunosorbent assay antibodies to RVF virus were also present in the same 24 serum samples. Indirect immunofluorescence was less sensitive in comparison with PRNT, and complement fixation was the least sensitive. These results extend observations made with laboratory animals to a large field-collected group of Egyptian sheep. PMID:3533977

Phytosociology and succession on earthquake-uplifted coastal wetlands, Copper River Delta, Alaska.

Treesearch

T.F. Thilenius

1995-01-01

The delta formed by the Copper River stretches more than 75 kilometers along the south-central coastline of Alaska. It is the terminus of the outwash deposits from a large part of the most heavily glaciated region of North American, and all major rivers that flow into the delta carry extremely high levels of suspended sediments. Coastal wetlands extend inland for as...

Large infrequently operated river diversions for Mississippi delta restoration

NASA Astrophysics Data System (ADS)

Day, John W.; Lane, Robert R.; D'Elia, Christopher F.; Wiegman, Adrian R. H.; Rutherford, Jeffrey S.; Shaffer, Gary P.; Brantley, Christopher G.; Kemp, G. Paul

2016-12-01

Currently the Mississippi delta stands as a highly degraded and threatened coastal ecosystem having lost about 25% of coastal wetlands during the 20th century. To address this problem, a 50 billion, 50-year restoration program is underway. A central component of this program is reintroduction of river water back into the deltaic plain to mimic natural functioning of the delta. However, opposition to diversions has developed based on a number of perceived threats. These include over-freshening of coastal estuaries, displacement of fisheries, perceived water quality problems, and assertions that nutrients in river water leads to wetland deterioration. In addition, growing climate impacts and increasing scarcity and cost of energy will make coastal restoration more challenging and limit restoration options. We address these issues in the context of an analysis of natural and artificial diversions, crevasse splays, and small sub-delta lobes. We suggest that episodic large diversions and crevasses (>5000 m3 s-1) can build land quickly while having transient impacts on the estuarine system. Small diversions (<200 m3 s-1) that are more or less continuously operated build land slowly and can lead to over-freshening and water level stress. We use land building rates for different sized diversions and impacts of large periodic inputs of river water to coastal systems in the Mississippi delta to conclude that high discharge diversions operated episodically will lead to rapid coastal restoration and alleviate concerns about diversions. Single diversion events have deposited sediments up to 40 cm in depth over areas up to 130-180 km2. This approach should have broad applicability to deltas globally.

Conceptual model of sedimentation in the Sacramento-San Joaquin River Delta

USGS Publications Warehouse

Schoellhamer, David H.; Wright, Scott A.; Drexler, Judith Z.

2012-01-01

Sedimentation in the Sacramento–San Joaquin River Delta builds the Delta landscape, creates benthic and pelagic habitat, and transports sediment-associated contaminants. Here we present a conceptual model of sedimentation that includes submodels for river supply from the watershed to the Delta, regional transport within the Delta and seaward exchange, and local sedimentation in open water and marsh habitats. The model demonstrates feedback loops that affect the Delta ecosystem. Submerged and emergent marsh vegetation act as ecosystem engineers that can create a positive feedback loop by decreasing suspended sediment, increasing water column light, which in turn enables more vegetation. Sea-level rise in open water is partially countered by a negative feedback loop that increases deposition if there is a net decrease in hydrodynamic energy. Manipulation of regional sediment transport is probably the most feasible method to control suspended sediment and thus turbidity. The conceptual model is used to identify information gaps that need to be filled to develop an accurate sediment transport model.

The Potential of Time Series Based Earth Observation for the Monitoring of Large River Deltas

NASA Astrophysics Data System (ADS)

Kuenzer, C.; Leinenkugel, P.; Huth, J.; Ottinger, M.; Renaud, F.; Foufoula-Georgiou, E.; Vo Khac, T.; Trinh Thi, L.; Dech, S.; Koch, P.; Le Tissier, M.

2015-12-01

Although river deltas only contribute 5% to the overall land surface, nearly six hundred million people live in these complex social-ecological environments, which combine a variety of appealing locational advantages. In many countries deltas provide the major national contribution to agricultural and industrial production. At the same time these already very dynamic environments are exposed to a variety of threats, including the disturbance and replacement of valuable ecosystems, increasing water, soil, and air pollution, human induced land subsidence, sea level rise, as well upstream developments impacting water and sediment supplies. A constant monitoring of delta systems is thus of utmost relevance for understanding past and current land surface change and anticipating possible future developments. We present the potential of Earth Observation based analyses and derived novel information products that can play a key role in this context. Along with the current trend of opening up numerous satellite data archives go increasing capabilities to explore big data. Whereas in past decades remote sensing data were analysed based on the spectral-reflectance-defined 'finger print' of individual surfaces, we mainly exploit the 'temporal fingerprints' of our land surface in novel pathways of data analyses at differing spatial-, and temporally-dense scales. Following our results on an Earth Observation based characterization of large deltas globally, we present in depth results from the Mekong Delta in Vietnam, the Yellow River Delta in China, the Niger Delta in Nigeria, as well as additional deltas, focussing on the assessment of river delta flood and inundation dynamics, river delta coastline dynamics, delta morphology dynamics including the quantification of erosion and accretion processes, river delta land use change and trends, as well as the monitoring of compliance to environmental regulations.

Morphodynamics and Sediment Transport on the Huanghe (Yellow River) Delta: Work in Progress

NASA Astrophysics Data System (ADS)

Kineke, G. C.; Calson, B.; Chadwick, A. J.; Chen, L.; Hobbs, B. F.; Kumpf, L. L.; Lamb, M. P.; Ma, H.; Moodie, A. J.; Mullane, M.; Naito, K.; Nittrouer, J. A.; Parker, G.

2017-12-01

Deltas are perhaps the most dynamic of coastal landforms with competing processes that deliver and disperse sediment. As part of the NSF Coastal SEES program, an interdisciplinary team of scientists from the US and China are investigating processes that link river and coastal sediment transport responsible for morphodynamic change of the Huanghe delta- an excellent study site due to its high sediment load and long history of natural and engineered avulsions, that is, abrupt shifts in the river course. A fundamental component of the study is a better understanding of sediment transport physics in a river system that transports mostly silt. Through theory and data analysis, we find that fine-grained rivers fail to develop full scale dunes, which results in faster water flow and substantially larger sediment fluxes as compared to sandy rivers (e.g. the Mississippi River). We also have developed new models for sediment-size dependent entrainment that are needed to make longer term predictions of river sedimentation patterns. On the delta front, we are monitoring the high sediment flux to the coast, which results in steep foresets and ideal conditions for off-shore sediment delivery via gravity flows. These constraints on sediment transport are being used to develop new theory for where and when rivers avulse - including the effects of variable flood discharge, sediment supply, and sea level rise -and how deltas ultimately grow through repeated cycles of lobe development. Flume experiments and field observations are being used to test these models, both in the main channel of the Huanghe and in channels abandoned after historic avulsions. Abandoned channels and floodplains are now dominated by coastal sediment transport through a combination of wave resuspension and tidal transport, settling lag and reverse estuarine circulation. Finally, the field and laboratory tested numerical models are being used as inputs to define a cost curve for efficient avulsion management of

What role do hurricanes play in sediment delivery to subsiding river deltas?

USGS Publications Warehouse

Smith, James E.; Bentley, Samuel J.; Snedden, Gregg; White, Crawford

2015-01-01

The Mississippi River Delta (MRD) has undergone tremendous land loss over the past century due to natural and anthropogenic influences, a fate shared by many river deltas globally. A globally unprecedented effort to restore and sustain the remaining subaerial portions of the delta is now underway, an endeavor that is expected to cost $50–100B over the next 50 yr. Success of this effort requires a thorough understanding of natural and anthropogenic controls on sediment supply and delta geomorphology. In the MRD, hurricanes have been paradoxically identified as both substantial agents of widespread land loss, and vertical marsh sediment accretion. We present the first multi-decadal chronostratigraphic assessment of sediment supply for a major coastal basin of the MRD that assesses both fluvial and hurricane-induced contributions to sediment accumulation in deltaic wetlands. Our findings indicate that over multidecadal timescales, hurricane-induced sediment delivery may be an important contributor for deltaic wetland vertical accretion, but the contribution from hurricanes to long-term sediment accumulation is substantially less than sediment delivery supplied by existing and planned river-sediment diversions at present-day river-sediment loads.

What Role do Hurricanes Play in Sediment Delivery to Subsiding River Deltas?

NASA Astrophysics Data System (ADS)

Smith, James E.; Bentley, Samuel J.; Snedden, Gregg A.; White, Crawford

2015-12-01

The Mississippi River Delta (MRD) has undergone tremendous land loss over the past century due to natural and anthropogenic influences, a fate shared by many river deltas globally. A globally unprecedented effort to restore and sustain the remaining subaerial portions of the delta is now underway, an endeavor that is expected to cost $50-100B over the next 50 yr. Success of this effort requires a thorough understanding of natural and anthropogenic controls on sediment supply and delta geomorphology. In the MRD, hurricanes have been paradoxically identified as both substantial agents of widespread land loss, and vertical marsh sediment accretion. We present the first multi-decadal chronostratigraphic assessment of sediment supply for a major coastal basin of the MRD that assesses both fluvial and hurricane-induced contributions to sediment accumulation in deltaic wetlands. Our findings indicate that over multidecadal timescales, hurricane-induced sediment delivery may be an important contributor for deltaic wetland vertical accretion, but the contribution from hurricanes to long-term sediment accumulation is substantially less than sediment delivery supplied by existing and planned river-sediment diversions at present-day river-sediment loads.

Non-variceal upper gastrointestinal bleeding in cirrhotic patients in Nile Delta.

PubMed

Gabr, Mamdouh Ahmed; Tawfik, Mohamed Abd El-Raouf; El-Sawy, Abd Allah Ahmed

2016-01-01

Acute upper gastrointestinal bleeding (AUGIB) in cirrhotic patients occurs mainly from esophageal and gastric varices; however, quite a large number of cirrhotic patients bleed from other sources as well. The aim of the present work is to determine the prevalence of non-variceal UGIB as well as its different causes among the cirrhotic portal hypertensive patients in Nile Delta. Emergency upper gastrointestinal (UGI) endoscopy for AUGIB was done in 650 patients. Out of these patients, 550 (84.6%) patients who were proved to have cirrhosis were the subject of the present study. From all cirrhotic portal hypertensive patients, 415 (75.5%) bled from variceal sources (esophageal and gastric) while 135 (24.5%) of them bled from non-variceal sources. Among variceal sources of bleeding, esophageal varices were much more common than gastric varices. Peptic ulcer was the most common non-variceal source of bleeding. Non-variceal bleeding in cirrhosis was not frequent, and sources included peptic ulcer, portal hypertensive gastropathy, and erosive disease of the stomach and duodenum.

Climate Change Impacts, Vulnerabilities and Adaption Measures for Egypt's Nile Delta

NASA Astrophysics Data System (ADS)

Abutaleb, Khaled Abubakr Ali; Mohammed, Asmaa Hassan El-Sayed; Ahmed, Mahmoud H. Mohamed

2018-04-01

During the last few decades there has been growing concern about the impacts of climate change. A significant number of institutions, research centers, universities and governments have funded projects in addition to work done by independent scholars and assessors studying this phenomenon, in particular, to identify vulnerability, mitigation and adaptation against associated risks. Egypt is among the international community which took part in numerous studies, research activities, conferences, seminars and meetings attempting to address climate change and its associated risks. Egypt is particularly concerned with the threat to the Nile Delta as it is considered a low-lying land at high risk. The aim of this paper is to review current and previous projects, technical reports and pilot studies, concerning risk assessments, mitigation, and adaptation strategies for climate change in Egypt. This, in turn, will aid in decision making regarding future funding and establishing of research related to climate change in Egypt. This paper will also highlight the weaknesses and strengths of policymakers solely relying on one or more of these studies.

Estimating sediment budgets at the interface between rivers and estuaries with application to the Sacramento-San Joaquin River Delta

USGS Publications Warehouse

Wright, S.A.; Schoellhamer, D.H.

2005-01-01

[1] Where rivers encounter estuaries, a transition zone develops where riverine and tidal processes both affect sediment transport processes. One such transition zone is the Sacramento-San Joaquin River Delta, a large, complex system where several rivers meet to form an estuary (San Francisco Bay). Herein we present the results of a detailed sediment budget for this river/estuary transitional system. The primary regional goal of the study was to measure sediment transport rates and pathways in the delta in support of ecosystem restoration efforts. In addition to achieving this regional goal, the study has produced general methods to collect, edit, and analyze (including error analysis) sediment transport data at the interface of rivers and estuaries. Estimating sediment budgets for these systems is difficult because of the mixed nature of riverine versus tidal transport processes, the different timescales of transport in fluvial and tidal environments, and the sheer complexity and size of systems such as the Sacramento-San Joaquin River Delta. Sediment budgets also require error estimates in order to assess whether differences in inflows and outflows, which could be small compared to overall fluxes, are indeed distinguishable from zero. Over the 4 year period of this study, water years 1999-2002, 6.6 ?? 0.9 Mt of sediment entered the delta and 2.2 ?? 0.7 Mt exited, resulting in 4.4 ?? 1.1 Mt (67 ?? 17%) of deposition. The estimated deposition rate corresponding to this mass of sediment compares favorably with measured inorganic sediment accumulation on vegetated wetlands in the delta.

Reading Ombrone river delta evolution through beach ridges morphology

NASA Astrophysics Data System (ADS)

Mammi, Irene; Piccardi, Marco; Pranzini, Enzo; Rossi, Lorenzo

2017-04-01

The present study focuses on the evolution of the Ombrone River delta (Southern Tuscany, Italy) in the last five centuries, when fluvial sediment input was huge also as a consequence of the deforestation performed on the watershed. The aim of this study is to find a correlation between river input and beach ridges morphology and to explain the different distribution of wetlands and sand deposits on the two sides of the delta. Visible, NIR and TIR satellite images were processed to retrieve soil wetness associated to sand ridges and interdune silty deposits. High resolution LiDAR data were analysed using vegetation filter and GIS enhancement algorithms in order to highlight small morphological variations, especially in areas closer to the river where agriculture has almost deleted these morphologies. A topographic survey and a very high resolution 3D model obtained from a set of images acquired by an Unmanned Aerial Vehicle (UAV) were carried out in selected sites, both to calibrate satellite LiDAR 3D data, and to map low relief areas. Historical maps, aerial photography and written documents were analysed for dating ancient shorelines associated to specific beach ridges. Thus allowing the reconstruction of erosive and accretive phases of the delta. Seventy beach ridges were identified on the two wings of the delta. On the longer down-drift side (Northern wing) beach ridges are more spaced at the apex and gradually converge to the extremity, where the Bruna River runs and delimits the sub aerial depositional area of the Ombrone River. On the shorter up-drift lobe (Southern wing), beach ridges are closer, but run almost parallel each other. In this case, a rocky headland called Collelungo promontory closes and cuts the beach ridges sequence but shallow water depth allows sediment by pass. One kilometre to the south a more pronounced promontory encloses a small pocket beach (Cala di Forno) and identifies the limit of the subaerial depositionary area. Beach ridges

Characterization of transboundary POP contamination in aquatic ecosystems of Pearl River delta.

PubMed

Chau, K W

2005-01-01

During the past two decades, the rapid development of the Pearl River delta leads to substantial accumulation of various toxic organic compounds. This study aims to give a preliminary characterization of the existing state of contamination in this region and to provide insight into the possible fate of persistent organic pollutants (POPs) in this estuary. The available data on POPs in water, river, estuarine sediments, soil, and marine organisms within the Pearl River delta are compiled. It is shown that it may lead to transboundary POP pollution problems at both Hong Kong and Macau Special Administration Regions located at the downstream end of the region. It is noted that the levels of DDTs and HCHs in various environmental media are at alerting levels and that fresh DDT might still be applied illegally within the region. A systematic research is required to determine both the temporal and spatial variations of all POPs in various carrying media of the Pearl River delta as a whole.

Mississippi River Delta, Louisiana as seen from STS-62

NASA Technical Reports Server (NTRS)

1994-01-01

The Mississippi River Delta, Louisiana as seen from STS-62, is the largest river system in North America. The interdistributary bays are extremely shallow, usually less than a few meters, and contain brackish to normal marine waters except during times of flooding, when fresh water fills the bays. Sedimentation within the bays is very low, occurring only during flood periods. Along the west side of the river, a highway has been built southeastward to Venice.

The Siná river delta on the northwestern Caribbean coast of Colombia: Bay infilling associated with delta development

NASA Astrophysics Data System (ADS)

Suarez, Beatriz Elena Serrano

2004-04-01

Between 1938 and 1945, the Sinú River changed its course and started a new delta at a site known as Tinajones. The change took place after the infilling of Cispata Bay, the site of the previous delta. The infilling is studied with two isopach maps made from bathymetric charts from 1762, 1849, and 1938. The isopachs help show the distribution of the sediments inside the bay and provide estimations of sedimentation rates. The results are compared with the sediment distribution and estimated sedimentation rate found for the delta at Tinajones. The results suggest that the infilling of the Cispata Bay produced the river avulsion and the change to Tinajones and probably was accelerated by sediments that came from outside the bay.

Stereo Anaglyphs of River Meanders in Eberswalde Delta

NASA Image and Video Library

2007-01-10

This anaglyph from NASA Mars Reconnaissance Orbiter spacecraft, shows that Eberswalde Delta contains river meanders, which indicate that flowing water was present for an extended period of time. 3D glasses are necessary to view this image.

The influence of delta formation mechanism on geotechnical property sequence of the late Pleistocene-Holocene sediments in the Mekong River Delta.

PubMed

Hoang, Truong Minh; van Lap, Nguyen; Oanh, Ta Thi Kim; Jiro, Takemura

2016-11-01

The aim of the study was to characterize a variety of microstructure development-levels and geotechnical property sequences of the late Pleistocene-Holocene deposits in the Mekong River delta (MRD), and the paper furthermore discusses the influences of delta formation mechanisms on them. The survey associated the geotechnical engineering and the sedimentary geology of the late Pleistocene-Holocene deposits at five sites and also undifferentiated Pleistocene sediments. A cross-section which was rebuilt in the delta progradation-direction and between the Mekong and Bassac rivers represents the stratigraphy. Each sedimentary unit was formed under a different delta formation mechanism and revealed a typical geotechnical property sequence. The mechanical behaviors of the sediment succession in the tide-dominated delta with significant fluvial-activity and material source tend to be more cohesionless soils and strengths than those in the tide- and wave-dominated delta and even the coast. The particular tendency of the mechanical behavior of the deposit succession can be reasonably estimated from the delta formation mechanism. The characteristics of the clay minerals from the Mekong River produced the argillaceous soil which does not have extremely high plasticity. The microstructure development-levels are low to very high indicating how to choose hydraulic conductivity value, k, for estimating overconsolidation ratio, OCR, by the piezocone penetration tests (CPTU). The OCR of sediments in the delta types strangely change with depth but none less than 1. The post-depositional processes significantly influenced the microstructure development, particularly the dehydrating and oxidizing processes.

Linking rapid erosion of the Mekong River delta to human activities

PubMed Central

Anthony, Edward J.; Brunier, Guillaume; Besset, Manon; Goichot, Marc; Dussouillez, Philippe; Nguyen, Van Lap

2015-01-01

As international concern for the survival of deltas grows, the Mekong River delta, the world’s third largest delta, densely populated, considered as Southeast Asia’s most important food basket, and rich in biodiversity at the world scale, is also increasingly affected by human activities and exposed to subsidence and coastal erosion. Several dams have been constructed upstream of the delta and many more are now planned. We quantify from high-resolution SPOT 5 satellite images large-scale shoreline erosion and land loss between 2003 and 2012 that now affect over 50% of the once strongly advancing >600 km-long delta shoreline. Erosion, with no identified change in the river’s discharge and in wave and wind conditions over this recent period, is consistent with: (1) a reported significant decrease in coastal surface suspended sediment from the Mekong that may be linked to dam retention of its sediment, (2) large-scale commercial sand mining in the river and delta channels, and (3) subsidence due to groundwater extraction. Shoreline erosion is already responsible for displacement of coastal populations. It is an additional hazard to the integrity of this Asian mega delta now considered particularly vulnerable to accelerated subsidence and sea-level rise, and will be exacerbated by future hydropower dams. PMID:26446752

Ecosystem Services Assessment of the Nemunas River Delta

EPA Science Inventory

The concept of ecosystem services recognizes the services, and benefits, provided to people by ecosystems. The Nemunas River Delta, in Lithuania, provides many ecosystem services to the people of the area, including food, fuel, transportation, climate regulation, water purificati...

Tidal impact on the division of river discharge over distributary channels in the Mahakam Delta

NASA Astrophysics Data System (ADS)

Sassi, Maximiliano G.; Hoitink, A. J. F.; de Brye, Benjamin; Vermeulen, Bart; Deleersnijder, Eric

2011-12-01

Bifurcations in tidally influenced deltas distribute river discharge over downstream channels, asserting a strong control over terrestrial runoff to the coastal ocean. Whereas the mechanics of river bifurcations is well-understood, junctions in tidal channels have received comparatively little attention in the literature. This paper aims to quantify the tidal impact on subtidal discharge distribution at the bifurcations in the Mahakam Delta, East Kalimantan, Indonesia. The Mahakam Delta is a regular fan-shaped delta, composed of a quasi-symmetric network of rectilinear distributaries and sinuous tidal channels. A depth-averaged version of the unstructured-mesh, finite-element model second-generation Louvain-la-Neuve Ice-ocean Model has been used to simulate the hydrodynamics driven by river discharge and tides in the delta channel network. The model was forced with tides at open sea boundaries and with measured and modeled river discharge at upstream locations. Calibration was performed with water level time series and flow measurements, both spanning a simulation period. Validation was performed by comparing the model results with discharge measurements at the two principal bifurcations in the delta. Results indicate that within 10 to 15 km from the delta apex, the tides alter the river discharge division by about 10% in all bifurcations. The tidal impact increases seaward, with a maximum value of the order of 30%. In general, the effect of tides is to hamper the discharge division that would occur in the case without tides.

Shallow stratigraphy of the Skagit River Delta, Washington, derived from sediment cores

USGS Publications Warehouse

Grossman, Eric E.; George, Douglas A.; Lam, Angela

2011-01-01

Sedimentologic analyses of 21 sediment cores, ranging from 0.4 to 9.6 m in length, reveal that the shallow geologic framework of the Skagit River Delta, western Washington, United States, has changed significantly since 1850. The cores collected from elevations of 3.94 to -2.41 m (relative to mean lower low water) along four cross-shore transects between the emergent marsh and delta front show relatively similar environmental changes across an area spanning ~75 km2. Offshore of the present North Fork Skagit River and South Fork Skagit River mouths where river discharge is focused by diked channels through the delta, the entire 5–7-km-wide tidal flats are covered with 1–2 m of cross-bedded medium-to-coarse sands. The bottoms of cores, collected in these areas are composed of mud. A sharp transition from mud to a cross-bedded sand unit indicates that the tidal flats changed abruptly from a calm environment to an energetic one. This is in stark contrast to the Martha's Bay tidal flats north of the Skagit Bay jetty that was completed in the 1940s to protect the newly constructed Swinomish Channel from flooding and sedimentation. North of the jetty, mud ranging from 1 to 2 m thick drapes a previously silt- and sand-rich tidal flat. The silty sand is a sediment facies that would be expected there where North Fork Skagit River sedimentation occurred prior to jetty emplacement. This report describes the compositional and textural properties of the sediment cores by using geophysical, photographic, x-radiography, and standard sediment grain-size and carbon-analytical methods. The findings help to characterize benthic habitat structure and sediment transport processes and the environmental changes that have occurred across the nearshore of the Skagit River Delta. The findings will be useful for quantifying changes to nearshore marine resources, including impacts resulting from diking, river-delta channelization, shoreline development, and natural variations in fluvial

InSAR-based detection of McKenzie River Delta Permafrost loss

NASA Astrophysics Data System (ADS)

Oliver-Cabrera, T.; Wdowinski, S.

2017-12-01

Permafrost underlies most of the McKenzie River, North America's largest delta. The in the delta is catalogued as discontinuous permafrost due to the influence of shifting river channels on near-surface ground temperatures. The area is affected by climate change, studies show that ground temperature has increased by 1.5°C since 1970, due to rising annual mean air temperature. Flooding regimes within the delta are also affected by the changing climate due to melting of near surface ground ice together with sea-level rise increasing the potential of land subsidence. Observed consequences of changes occurring in the region are vegetation growth and northward migration of the tree line. The growing vegetation can affect physical properties of the accumulated snow, including depth, density and thermal conductivity. Thogether these variations affect permafrost stability. Permafrost changes can be measured throughout the impacts on river runoffs, ground water, drainages, carbon release, land subsidence and even infrastructure damages. Degradation of permafrost can also be measured by observing ecological changes in the area. In this study, we use InSAR observations to detect permafrost changes and their transition to wetland or vegetated land cover. Our data consist of four ALOS-PALSAR frames covering the entire McKenzie River Delta with temporal coverage spanning from January 2007 to March of 2011. Each frame has 20 to 24 acquisitions, in which half of the data acquired with HH polarization and the other half with HH+HV. We process the data using ROI_PAC and PYSAR software packages. Preliminary results have detected the following spatial patterns: (1) An overall good coherence of summer interferograms with 46-92 day interferograms, (2) Low coherence of winter interferograms (November to February), probably to the increase in snow coverage, (3) Phase jumps along the border of the river reflecting morphological differences between the region near to the river and other

Flow patterns and bathymetric signatures on the delta front of a prograding river delta

NASA Astrophysics Data System (ADS)

Shaw, J.; Mohrig, D. C.; Wagner, R. W.

2016-02-01

The transition of water between laterally confined channels and the unchannelized delta front controls the growth pattern of river deltas, but is difficult to measure on field-scale deltas. We quantify flow patterns, bathymetry and bathymetric evolution for the subaqueous delta front on the Wax Lake Delta (WLD), a rapidly prograding delta in coastal Louisiana. The flow direction field, mapped using streaklines composed of biogenic slicks on the water surface, shows that a significant portion of flow ( 59%) departs subaqueous channels laterally over the subaqueous margins of the channel seaward of the shoreline. Synoptic datasets of bathymetry and flow direction allow spatial changes in flow velocity to be quantified. Most lateral flow divergence and deceleration occurs within 3-8 channel widths outboard of subaqueous channel margins, rather than downstream of channel tips. In interdistributary bays, deposit elevation decreases with a basinward slope of 2.4 x 10-4 with distance from a channel margin along any flow path. Flow patterns and this slope produce constructional features called interdistributary troughs - topographic lows in the center of interdistributary bays. These data show that flow patterns and bathymetry on the delta front are coupled both at the transition from channelized to unchannelized flow and in the depositional regions outside the distributary network.

Recent Niger Delta shoreline response to Niger River hydrology: Conflict between forces of Nature and Humans

NASA Astrophysics Data System (ADS)

Dada, Olusegun A.; Li, Guangxue; Qiao, Lulu; Asiwaju-Bello, Yinusa Ayodele; Anifowose, Adeleye Yekini Biodun

2018-03-01

The Niger River Delta is a prolific hydrocarbon province and a mega-delta of economic and environmental relevance. To understand patterns of its recent shoreline evolution (1923-2013) in response to the Niger River hydrology, and establish the role played by forces of Nature and Human, available topographic and satellite remote sensing data, combined with hydro-climatic (rainfall and runoff) data were analyzed. Results indicate that the entire delta coastline dramatically receded: 82% of the >400 km-long coast retreated, during the period 1950-1987; and 69% between 2007 and 2012. Prior to 1950, there was a continuation of seaward advancement along 53-74% of the delta coast. The 1950-1987 shoreline recession coincided with occurrences of two major events in the Niger River basin; these are downward trends in hydro-climatic conditions (the great droughts of the 1970s-1980s), and dam construction on the Lower Niger River at Kainji (1964-1968). The 2007-2012 event corresponded with the extensive channel dredging during 2009-2012 in the Lower Niger River from the coastal town of Warri in the south to Baro in the north. Remarkably, the largest net shoreline advancement recorded in 74% of the entire delta area occurred within a year (2012-2013), which we link to increased sediment supply to the coast caused by the '2012' floods, adjudged the worst floods in the entire Niger River Basin in the last few decades. With both anthropogenic and environmental factors inducing delta evolution, only innovative river and coastal management can determine the fortune of the future coastal development of the Niger Delta.

STS-65 Earth observation of Omo River Delta, Lake Turkana in Ethiopia / Kenya

NASA Technical Reports Server (NTRS)

1994-01-01

STS-65 Earth observation taken aboard Columbia, Orbiter Vehicle (OV) 102, is of Omo River Delta and Lake Turkana in Ethiopia / Kenya. The Omo Delta at the north end of Lake Turkana (Rudolph) is one of the long-term environmental study sites of the Space Shuttle program. The environmental interest in this instance is the documentation of the delta's extension into the lake. This delta extension, or aggradation, is felt to be the result of large-scale soil erosion in the recently deforested areas of Ethiopia in the watershed of the Omo River. Using digitized, rectified, machine-classified, and mensurated NASA photography, it has been determined that the Omo Delta has increased in area by approximately 400% to about 1,800 square kilometers since it was first photographed during the Gemini program in 1965. This photograph documents the long-term and increasing turbidity of Lake Turkana and the continuing delta extension southward by both the northwest and northeast distributaries of the Om

River delta network hydraulic residence time distributions and their role in coastal nutrient biogeochemistry

NASA Astrophysics Data System (ADS)

Hiatt, M. R.; Castaneda, E.; Twilley, R.; Hodges, B. R.; Passalacqua, P.

2015-12-01

River deltas have the potential to mitigate increased nutrient loading to coastal waters by acting as biofilters that reduce the impact of nutrient enrichment on downstream ecosystems. Hydraulic residence time (HRT) is known to be a major control on biogeochemical processes and deltaic floodplains are hypothesized to have relatively long HRTs. Hydrological connectivity and delta floodplain inundation induced by riverine forces, tides, and winds likely alter surface water flow patterns and HRTs. Since deltaic floodplains are important elements of delta networks and receive significant fluxes of water, sediment, and nutrients from distributary channels, biogeochemical transformations occurring within these zones could significantly reduce nutrient loading to coastal receiving waters. However, network-scale estimates of HRT in river deltas are lacking and little is known about the effects of tides, wind, and the riverine input on the HRT distribution. Subsequently, there lacks a benchmark for evaluating the impact of engineered river diversions on coastal nutrient ecology. In this study, we estimate the HRT of a coastal river delta by using hydrodynamic modeling supported by field data and relate the HRT to spatial and temporal patterns in nitrate levels measured at discrete stations inside a delta island at Wax Lake Delta. We highlight the control of the degree of hydrological connectivity between distributary channels and interdistributary islands on the network HRT distribution and address the roles of tides and wind on altering the shape of the distribution. We compare the observed nitrate concentrations to patterns of channel-floodplain hydrological connectivity and find this connectivity to play a significant role in the nutrient removal. Our results provide insight into the potential role of deltaic wetlands in reducing the nutrient loading to near-shore waters in response to large-scale river diversions.

Impacts of Declining Mississippi River Sediment Load on Subaqueous Delta Front Sedimentation and Geomorphology

NASA Astrophysics Data System (ADS)

Maloney, J. M.; Bentley, S. J.; Xu, K.; Georgiou, I. Y.; Miner, M. D.

2016-02-01

The Mississippi River delta system is undergoing unprecedented changes due to the effects of climate change and anthropogenic alterations to the river and its delta. Since the 1950s, the suspended sediment load of the Mississippi River has decreased by approximately 50% due to the construction of >50,000 dams in the Mississippi basin. The impact of this decreased sediment load has been observed in subaerial environments, but the impact on sedimentation and geomorphology of the subaqueous delta front has yet to be examined. To identify historic trends in sedimentation patterns, we compiled bathymetric datasets, including historical charts, industry and academic surveys, and NOAA data, collected between 1764 and 2009. Sedimentation rates are variable across the delta front, but are highest near the mouth of Southwest Pass, which carries the largest percentage of Mississippi River flow and sediment into the Gulf of Mexico. The progradation rate of Southwest Pass (measured at the 10 m depth contour) has slowed from 67 m/yr between 1764 and 1940 to 26 m/yr between 1940 and 1979, with evidence of further deceleration from 1979-2009. Decreased rates of progradation are also observed at South Pass and Pass A Loutre, with the 10 m contour retreating at rates >20 m/yr at both passes. Advancement of the delta front also decelerated in deeper water (15-90 m) offshore from Southwest Pass. In this area, from 1940-1979, depth contours advanced seaward 30 m/yr, but rates declined from 1979-2005. Furthermore, over the same area, the sediment accumulation rate decreased by 81% for the same period. The Mississippi River delta front appears to be entering a phase of decline, which will likely be accelerated by future upstream management practices. This decline has implications for offshore ecosystems, biogeochemical cycling, pollutant dispersal, mudflow hazard, and the continued use of the delta as an economic and population center.

Grain size controls on the morphology and stratigraphy of river-dominated deltas

NASA Astrophysics Data System (ADS)

Burpee, Alex; Parsons, Daniel; Slingerland, Rudy; Edmonds, Doug; Best, Jim; Cederberg, James; McGuffin, Andrew; Caldwell, Rebecca; Nijhuis, Austin

2015-04-01

The proportions of sand and mud that make up a river-dominated delta strongly determine its topset morphology, which in turn controls its internal facies and clinoform geometry. These relationships allow prediction of the stratigraphy of a delta using the character of its topset and reconstruction of deltaic planform from measures of clinoform geometry. This paper presents results from the Delft3D modeling system which was used to simulate nine self-formed deltas that possess different sediment loads and critical shear stresses that are required for re-entrainment of mud. The simulated deltas were set to prograde into a shallow basin without waves, tides, Coriolis forcing, and buoyancy. Model results indicate that sand-dominated deltas are more fan-shaped whilst mud-dominated deltas are more birdsfoot in planform, because the sand-dominated deltas have more active distributaries, a smaller variance of topset elevations, and thereby experience a more equitable distribution of sediment to their perimeters. This results in a larger proportion of channel facies in sand-dominated deltas, and more uniformly-distributed clinoform dip directions, steeper dips, and greater clinoform concavity. These conclusions are consistent with data collected from the Goose River Delta, a coarse-grained fan delta prograding into Goose Bay, Labrador, Canada and also allow us to undertake a re-interpretation of the Kf-1 parasequence set of the Cretaceous Last Chance Delta, a unit of the Ferron Sandstone near Emery, Utah, USA. We argue that the Last Chance delta likely possessed numerous distributaries with at least five orders of bifurcation.

The White Nile sedimentary system

NASA Astrophysics Data System (ADS)

Garzanti, Eduardo; Andò, Sergio; Padoan, Marta; Resentini, Alberto; Vezzoli, Giovanni; Villa, Igor

2014-05-01

The Nile River flows for ~6700 km from south of the Equator to finally reach the Mediterranean Sea at northern subtropical latitudes (Woodward et al. 2007). This is the longest sedimentological laboratory on Earth, a unique setting in which we are investigating changes in sediment composition associated with diverse chemical and physical processes, including weathering and hydraulic sorting. The present study focuses on the southern branch of the Nile across 20° of latitude, from hyperhumid Burundi and Rwanda highlands in central Africa to Khartoum, the capital city of Sudan at the southern edge of the Sahara. Our study of the Kagera basin emphasizes the importance of weathering in soils at the source rather than during stepwise transport, and shows that the transformation of parent rocks into quartzose sand may be completed in one sedimentary cycle (Garzanti et al. 2013a). Micas and heavy minerals, less effectively diluted by recycling than main framework components, offer the best key to identify the original source-rock imprint. The different behaviour of chemical indices such as the CIA (a truer indicator of weathering) and the WIP (markedly affected by quartz dilution) helps us to distinguish strongly weathered first-cycle versus polycyclic quartz sands (Garzanti et al. 2013b). Because sediment is efficiently trapped in East African Rift lakes, the composition of Nile sediments changes repeatedly northwards across Uganda. Downstream of both Lake Kyoga and Lake Albert, quartzose sands are progressively enriched in metamorphiclastic detritus supplied from tributaries draining amphibolite-facies basements. The evolution of White Nile sediments across South Sudan, a scarcely accessible region that suffered decades of civil war, was inferred from the available information (Shukri 1950), integrated by original petrographic, heavy-mineral and geochemical data (Padoan et al. 2011). Mineralogical and isotopic signatures of Bahr-el-Jebel and Sobat sediments, derived

Asynchronous changes in vegetation, runoff and erosion in the nile river watershed during the holocene.

PubMed

Blanchet, Cécile L; Frank, Martin; Schouten, Stefan

2014-01-01

The termination of the African Humid Period in northeastern Africa during the early Holocene was marked by the southward migration of the rain belt and the disappearance of the Green Sahara. This interval of drastic environmental changes was also marked by the initiation of food production by North African hunter-gatherer populations and thus provides critical information on human-environment relationships. However, existing records of regional climatic and environmental changes exhibit large differences in timing and modes of the wet/dry transition at the end of the African Humid Period. Here we present independent records of changes in river runoff, vegetation and erosion in the Nile River watershed during the Holocene obtained from a unique sedimentary sequence on the Nile River fan using organic and inorganic proxy data. This high-resolution reconstruction allows to examine the phase relationship between the changes of these three parameters and provides a detailed picture of the environmental conditions during the Paleolithic/Neolithic transition. The data show that river runoff decreased gradually during the wet/arid transition at the end of the AHP whereas rapid shifts of vegetation and erosion occurred earlier between 8.7 and ∼6 ka BP. These asynchronous changes are compared to other regional records and provide new insights into the threshold responses of the environment to climatic changes. Our record demonstrates that the degradation of the environment in northeastern Africa was more abrupt and occurred earlier than previously thought and may have accelerated the process of domestication in order to secure sustainable food resources for the Neolithic African populations.

Ecosystem Services Assessment of the Nemunas River Delta

EPA Science Inventory

The concept of ecosystem services recognizes the services, and benefits, provided to people by ecosystems. The Nemunas River Delta, in Lithuania, is a valued area that can provide a range of services. We conducted a meta-analysis of existing studies done on the region to identify...

Bathymetry of the Hong and Luoc River Junction, Red River Delta, Vietnam, 2010

USGS Publications Warehouse

Kinzel, Paul J.; Nelson, Jonathan M.; Toan, Duong Duc; Thanh, Mung Dinh; Shimizu, Yasuyuki

2012-01-01

The U.S. Geological Survey, in collaboration with the Water Resources University in Hanoi, Vietnam, conducted a bathymetric survey of the junction of the Hong and Luoc Rivers. The survey was done to characterize the channel morphology of this delta distributary network and provide input for hydrodynamic and sediment transport models. The survey was carried out in December 2010 using a boat-mounted multibeam echo sounder integrated with a global positioning system. A bathymetric map of the Hong and Luoc River junction was produced which was referenced to the datum of the Trieu Duong tide gage on the Luoc River.

The geomorphological evidences of subsidence in the Nile Delta: Analysis of high resolution topographic DEM and multi-temporal satellite images

NASA Astrophysics Data System (ADS)

El Bastawesy, M.; Cherif, O. H.; Sultan, M.

2017-12-01

This paper investigates the relevance of landforms to the subsidence of the Nile Delta using a high resolution topographic digital elevation model (DEM) and sets of multi-temporal Landsat satellite images. 195 topographic map sheets produced in 1946 at 1:25,000 scale were digitized, and the DEM was interpolated. The undertaken processing techniques have distinguished all the natural low-lying closed depressions from the artificial errors induced by the interpolation of the DEM. The local subsidence of these depressions from their surroundings reaches a maximum depth of 2.5 m. The regional subsidence of the Nile Delta has developed inverted topography, where the tracts occupied by the contemporary distributary channels are standing at higher elevations than the areas in between. This inversion could be related to the differences in the hydrological and sedimentological properties of underlying sediments, as the channels are underlain by water-saturated sands while the successions of clay and silt on flood plains are prone to compaction. Furthermore, the analysis of remote sensing and topographic data clearly show significant changes in the land cover and land use, particularly in the northern lagoons and adjacent sabkhas, which are dominated by numerous low subsiding depressions. The areas covered by water logging and ponds are increasing on the expense of agricultural areas, and aquaculture have been practiced instead. The precise estimation of subsidence rates and distribution should be worked out to evaluate probable changes in land cover and land use.

More than 100 Years of Background-Level Sedimentary Metals, Nisqually River Delta, South Puget Sound, Washington

USGS Publications Warehouse

Takesue, Renee K.; Swarzenski, Peter W.

2011-01-01

The Nisqually River Delta is located about 25 km south of the Tacoma Narrows in the southern reach of Puget Sound. Delta evolution is controlled by sedimentation from the Nisqually River and erosion by strong tidal currents that may reach 0.95 m/s in the Nisqually Reach. The Nisqually River flows 116 km from the Cascade Range, including the slopes of Mount Rainier, through glacially carved valleys to Puget Sound. Extensive tidal flats on the delta consist of late-Holocene silty and sandy strata from normal river streamflow and seasonal floods and possibly from distal sediment-rich debris flows associated with volcanic and seismic events. In the early 1900s, dikes and levees were constructed around Nisqually Delta salt marshes, and the reclaimed land was used for agriculture and pasture. In 1974, U.S. Fish and Wildlife Service established the Nisqually National Wildlife Refuge on the reclaimed land to protect migratory birds; its creation has prevented further human alteration of the Delta and estuary. In October 2009, original dikes and levees were removed to restore tidal exchange to almost 3 km2 of man-made freshwater marsh on the Nisqually Delta.

Assessing Subaqueous Mudflow Hazard on the Mississippi River Delta Front, Part 1: A Historical Perspective on Mississippi River Delta Front Sedimentation

NASA Astrophysics Data System (ADS)

Maloney, J. M.; Bentley, S. J.; Obelcz, J.; Xu, K.; Miner, M. D.; Georgiou, I. Y.; Hanegan, K.; Keller, G.

2014-12-01

Subaqueous mudflows are known to be ubiquitous across the Mississippi River delta front (MRDF) and have been identified as a hazard to offshore infrastructure. Among other factors, sediment accumulation rates and patterns play an important role in governing the stability of delta front sediment. High sedimentation rates result in underconsolidation, slope steepening, and increased biogenic gas production, which are all known to decrease stability. Sedimentation rates are highly variable across the MRDF, but are highest near the mouth of Southwest Pass, which carries the largest percentage of Mississippi River sediment into the Gulf of Mexico. Since the 1950s, the sediment load of the Mississippi River has decreased by ~50% due to dam construction upstream. The impact of this decreased sediment load on MRDF mudflow dynamics has yet to be examined. We compiled MRDF bathymetric datasets, including historical charts, industry and academic surveys, and NOAA data, collected between 1764 and 2009, in order to identify historic trends in sedimentation patterns. The progradation of Southwest Pass (measured at 10 m depth contour) has slowed from ~66 m/yr between 1764 and 1940 to ~25 m/yr between 1940 and 1979, with evidence of further deceleration from 1979-2009. Decreased rates of progradation are also observed at South Pass and Pass A Loutre. Advancement of the delta also decelerated in deeper water (15-90 m) offshore from Southwest Pass. In this area, from 1940-1979, depth contours advanced seaward ~25 m/yr, but did not advance from 1979-2005. Furthermore, over the same area and time ranges, the sediment accumulation rate decreased by ~82%. We expect these sedimentation trends are occurring across the delta front, with potential impacts on spatial and temporal patterns of subaqueous mudflows. The MRDF appears to be entering a phase of decline, which will likely be accelerated by future upstream sediment diversion projects. New geophysical data will be required to assess

Permafrost Mobilization from the Watershed to the Colville River Delta: Evidence from Biomarkers and 14C Ramped Pyrolysis

NASA Astrophysics Data System (ADS)

Zhang, X.; Bianchi, T. S.; Cui, X.; Rosenheim, B. E.; Ping, C. L.; Kanevskiy, M. Z.; Hanna, A. M.; Allison, M. A.

2016-12-01

As temperatures in the Arctic rise abnormally fast, permafrost in the region is vulnerable to extensive thawing. This could release previously frozen organic carbon (OC) into the contemporary carbon cycle, giving a positive feedback on global warming. Recent research has found the presence of particulate permafrost in rivers, deltas, and continental shelves in the Arctic, but little direct evidence exists on the mechanism of transportation of previously frozen soils from watershed to the coast. The Colville River in northern Alaska is the largest North American Arctic River with a continuous permafrost within its watershed. Previous work has found evidence for the deposition of previously frozen soils in the Colville River delta (Schreiner et al., 2014). Here, we compared the bulk organic carbon thermal properties, ages of soils and river and delta sediments from the Colville River drainage system using 14C Ramped Pyrolysis and chemical biomarkers. Our data show that deep permafrost soils as well as river and delta sediments had similar pyrograms and biomarker signatures, reflecting transport of soils from watershed to the delta. Surface soil had pyrograms indicative of less stable (more biodegradable) OC than deeper soil horizons. Similarity in pyrograms of deep soils and river sediment indicated the limited contribution of surface soils to riverine particulate OC inputs. Sediments in the delta showed inputs of yedoma (ice-rich syngenetic permafrost with large ice wedges) from the watershed sources (e.g., river bank erosion) in addition to peat inputs, that were largely from coastal erosion.

Omo River Delta, Lake Turkana, Ethiopia/Kenya border, Africa

NASA Technical Reports Server (NTRS)

1991-01-01

As a result of land clearing operations in the local area, the Omo River Delta (4.5N, 36.0E) at the north end of Lake Turkana, on the Ethiopia/Kenya border has become enlarged through topsoil erosion. The delta measured 800 sq. km. in 1981 doubled to 1,600 sq. km. by 1988 and was up to 1,800 sq. km. in 1991. This is the same area where the Leaky Anthropological Team discovered the earliest remains of human ancestors.

Distribution and condition of larval and juvenile Lost River and shortnose suckers in the Williamson River Delta restoration project and Upper Klamath Lake, Oregon

USGS Publications Warehouse

Burdick, Summer M.; Brown, Daniel T.

2010-01-01

Federally endangered Lost River sucker (Deltistes luxatus) and shortnose sucker (Chasmistes brevirostris) were once abundant throughout their range but populations have declined. They were extirpated from several lakes in the 1920s and may no longer reproduce in others. Poor recruitment to the adult spawning populations is one of several reasons cited for the decline and lack of recovery of these species and may be the consequence of high mortality during juvenile life stages. High larval and juvenile sucker mortality may be exacerbated by an insufficient quantity of suitable or high quality rearing habitat. In addition, larval suckers may be swept downstream from suitable rearing areas in Upper Klamath Lake into Keno Reservoir, which is seasonally anoxic. The Nature Conservancy flooded about 3,600 acres (1,456 hectares) to the north of the Williamson River mouth (Tulana Unit) in October 2007 and about 1,400 acres (567 hectares) to the south and east of the Williamson River mouth (Goose Bay Unit) a year later to retain larval suckers in Upper Klamath Lake, create nursery habitat, and improve water quality. The U.S. Geological Survey joined a long-term research and monitoring program in collaboration with The Nature Conservancy, the Bureau of Reclamation, and Oregon State University in 2008 to assess the effects of the Williamson River Delta restoration on the early life-history stages of Lost River and shortnose suckers. The primary objectives of the research were to describe habitat colonization and use by larval and juvenile suckers and non-sucker fishes and to evaluate the effects of the restored habitat on the health and condition of juvenile suckers. This report summarizes data collected in 2009 by the U.S. Geological Survey as a part of this monitoring effort. The Williamson River Delta appeared to provide suitable rearing habitat for endangered larval Lost River and shortnose suckers in 2008 and 2009. Larval suckers captured in this delta typically were

Dependence of flow and transport through the Williamson River Delta, Upper Klamath Lake, Oregon, on wind, river inflow, and lake elevation

USGS Publications Warehouse

Wood, Tamara M.

2012-01-01

The hydrodynamic model of Upper Klamath and Agency Lakes, Oregon, was used to run 384 realizations of a numerical tracer experiment in order to understand the relative effects of wind, lake elevation, and Williamson River inflow on flow and transport (the movement of water and passively transported constituents) through the Williamson River Delta. Significant findings from this study include: * The replacement rate of water increased in Tulana and Goose Bay with increasing lake elevation, Williamson River inflow, and wind speed. * The fraction of Williamson River inflow passing through either side of the Delta increased with lake elevation and Williamson River inflow. * The partial replacement rate of water in Goose Bay with water from the Williamson River increased with wind speed. * The partial replacement rate of water in Tulana with water from the Williamson River decreased with wind speed. * Strong wind forcing at the water surface caused more of the Williamson River inflow to pass through Goose Bay than through Tulana. * Westerly to northwesterly winds result in more of the Williamson River inflow passing through the Goose Bay side of the Delta than through the Tulana side. * Regression models developed from the tracer experiments can be used to quantify the dependencies between transport and the independent variables to obtain rough estimates of useful quantities such as residence time and steady-state solute concentrations.

Investigating the Origin of Natural and Anthropogenic Deformation across the Nile Delta Using Radar Interferometry, GRACE, Modeling, and Field data

NASA Astrophysics Data System (ADS)

Gebremichael, E.; Sultan, M.; Becker, R.; El Bastawesy, M.; Cherif, O.; Emil, M.; Ahmed, M.; Fathy, K.; Karki, S.; Chouinard, K.

2016-12-01

We applied an integrated approach (radar interferometry, flood simulation, GRACE, GIS) to investigate the nature and distribution of land deformation in the Nile Delta and to identify the natural and anthropogenic controlling factors. Our methodology involved: (1) applying persistent scatterer interferometry (PSI) across the entire Delta (scenes: 108 level 0 scenes; Tracks: 4 tracks; time period: 2003-2010); (2) correcting the interferometry output for various phase contributing errors (e.g., atmosphere, orbit, etc.) and calibrating/validating the output against 3 GNSS GPS stations (2 in Alexandria, 1 in Helwan); (3) conducting spatial correlation (in a GIS environment) of the radar outputs with relevant remote sensing, subsurface, and geologic datasets; (4) simulating flood depth and inundation to investigate the spatial extent and depth of the Holocene sediments using the HEC-RAS software (inputs: DEM and monthly discharge data; period: 1871-1902), (5) identifying subsurface structures by processing 712 gridded field gravity data points in Geosoft Oasis Montaj software (Bouguer anomaly analysis), and (6) analyzing monthly (2002-2015) GRACE-derived TWS solutions (0.5° x 0.5° CSR mascons). Our findings include: (1) three main structural trends (E-W, NW-SE and NE-SW trending) were mapped across the Delta, (2) areas of high subsidence coincide with the distribution of relatively thick recent sediments (<3000 years), probably due to sediment compaction, in three settings: (a) areas susceptible to flooding from the Damietta and Rosetta branches (e.g., east Damietta branch; latitude 30.8° to 31.2°; longitude 31.2° to 31.6°), (b) areas susceptible to sediment deposition at bifurcation locations of primary channels (e.g., near Cairo) and, (c) areas where mapped faults intersect Damietta and Rosetta channels, change their course, and cause ponding of surface water and sediment deposition, (3) extraction of gas from the Abu Madi gas field in north central delta

Modern sediment characteristics and accumulation rates from the delta front to prodelta of the Yellow River (Huanghe)

NASA Astrophysics Data System (ADS)

Zhou, Liangyong; Liu, Jian; Saito, Yoshiki; Gao, Maosheng; Diao, Shaobo; Qiu, Jiandong; Pei, Shaofeng

2016-08-01

Since 1976, the main channel of the Yellow River (Huanghe) has been on the east side of the delta complex, and the river has prograded a broad new delta lobe in Laizhou Bay of the Bohai Sea. In 2012, extensive bathymetric and high-resolution seismic profiles were conducted and sediment cores were collected off the new delta lobe. This study examined delta sedimentation and morphology along a profile across the modern subaqueous Yellow River delta and into Laizhou Bay, by analyzing sediment radionuclides (137Cs, 210Pb and 7Be), sedimentary structure, grain-size composition, organic carbon content, and morphological changes between 1976 and 2012. The change in the bathymetric profile, longitudinal to the river's course, reveals subaqueous delta progradation during this period. The subbottom boundary between the new delta lobe sediment and the older seafloor sediment (before the 1976 course shift) was identified in terms of lithology and radionuclide distributions, and recognized as a downlap surface in the seismic record. The accumulation rate of the new delta lobe sediment is estimated to be 5-18.6 cm year-1 on the delta front slope, 2 cm year-1 at the toe of the slope, and 1-2 cm year-1 in the shelf areas of Laizhou Bay. Sediment facies also change offshore, from alternations of gray and brown sediment in the proximal area to gray bioturbated fine sediment in the distal area. Based on 7Be distribution, the shorter-term deposition rate was at least 20 cm year-1 in the delta front.

Geomorphic change and sediment transport during a small artificial flood in a transformed post-dam delta: The Colorado River delta, United States and Mexico

USGS Publications Warehouse

Mueller, Erich R.; Schmidt, John C.; Topping, David J.; Shafroth, Patrick B.; Rodríguez-Burgueño, Jesús Eliana; Ramírez-Hernández, Jorge; Grams, Paul E.

2017-01-01

The Colorado River delta is a dramatically transformed landscape. Major changes to river hydrology and morpho-dynamics began following completion of Hoover Dam in 1936. Today, the Colorado River has an intermittent and/or ephemeral channel in much of its former delta. Initial incision of the river channel in the upstream ∼50 km of the delta occurred in the early 1940s in response to spillway releases from Hoover Dam under conditions of drastically reduced sediment supply. A period of relative quiescence followed, until the filling of upstream reservoirs precipitated a resurgence of flows to the delta in the 1980s and 1990s. Flow releases during extreme upper basin snowmelt in the 1980s, flood flows from the Gila River basin in 1993, and a series of ever-decreasing peak flows in the late 1990s and early 2000s further incised the upstream channel and caused considerable channel migration throughout the river corridor. These variable magnitude post-dam floods shaped the modern river geomorphology. In 2014, an experimental pulse-flow release aimed at rejuvenating the riparian ecosystem and understanding hydrologic dynamics flowed more than 100 km through the length of the delta’s river corridor. This small artificial flood caused localized meter-scale scour and fill of the streambed, but did not cause further incision or significant bank erosion because of its small magnitude. Suspended-sand-transport rates were initially relatively high immediately downstream from the Morelos Dam release point, but decreasing discharge from infiltration losses combined with channel widening downstream caused a rapid downstream reduction in suspended-sand-transport rates. A zone of enhanced transport occurred downstream from the southern U.S.-Mexico border where gradient increased, but effectively no geomorphic change occurred beyond a point 65 km downstream from Morelos Dam. Thus, while the pulse flow connected with the modern estuary, deltaic sedimentary processes were not

Landsat View: Pearl River Delta, China

NASA Image and Video Library

2017-12-08

In 1979, China established two special economic zones around the Pearl River Delta, north of Hong Kong. This image, taken by Landsat 3 on October 19, 1973, shows that the region was rural when the zone was established. Plant-covered land, which is red in this false-color image, dominates the scene. Square grids are agriculture. By January 10, 2003, when Landsat 7 took this image, the Pearl River Delta was a densely populated urban corridor with several large cities. The urban areas are gray in this image. The region is a major manufacturing center with an economy the size of Taiwan’s. As of 2010, the Pearl River Economic Zone had a population of 36 million people. ---- NASA and the U.S. Department of the Interior through the U.S. Geological Survey (USGS) jointly manage Landsat, and the USGS preserves a 40-year archive of Landsat images that is freely available over the Internet. The next Landsat satellite, now known as the Landsat Data Continuity Mission (LDCM) and later to be called Landsat 8, is scheduled for launch in 2013. In honor of Landsat’s 40th anniversary in July 2012, the USGS released the LandsatLook viewer – a quick, simple way to go forward and backward in time, pulling images of anywhere in the world out of the Landsat archive. NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Is Solar Variability Reflected in the Nile River?

NASA Technical Reports Server (NTRS)

Ruzmaikin, Alexander; Feynman, Joan; Yung, Yuk L.

2006-01-01

We investigate the possibility that solar variability influences North African climate by using annual records of the water level of the Nile collected in 622-1470 A.D. The time series of these records are nonstationary, in that the amplitudes and frequencies of the quasi-periodic variations are time-dependent. We apply the Empirical Mode Decomposition technique especially designed to deal with such time series. We identify two characteristic timescales in the records that may be linked to solar variability: a period of about 88 years and one exceeding 200 years. We show that these timescales are present in the number of auroras reported per decade in the Northern Hemisphere at the same time. The 11-year cycle is seen in the Nile's high-water level variations, but it is damped in the low-water anomalies. We suggest a possible physical link between solar variability and the low-frequency variations of the Nile water level. This link involves the influence of solar variability on the atmospheric Northern Annual Mode and on its North Atlantic Ocean and Indian Ocean patterns that affect the rainfall over the sources of the Nile in eastern equatorial Africa.

Invasive aquatic vegetation management in the Sacramento-San Joaquin River Delta: status recommendations

USDA-ARS?s Scientific Manuscript database

Widespread growth of invasive aquatic vegetation is a major stressor to the Sacramento-San Joaquin River Delta, a region of significant agricultural, industrial, and ecological importance. Total invaded area in the Delta is increasing, with the risk of new invasions a continual threat. However, inva...

Holocene evolution of the Liaohe Delta, a tide-dominated delta formed by multiple rivers in Northeast China

NASA Astrophysics Data System (ADS)

He, Lei; Xue, Chunting; Ye, Siyuan; Laws, Edward Allen; Yuan, Hongming; Yang, Shixiong; Du, Xiaolei

2018-02-01

The Liaohe Delta in Northeast China is one of the ecologically important estuarine deltas in China. It has been formed via the accumulation of sediment discharged by four rivers in the Liaohe Plain that enter Liaodong Bay. Twenty-seven 30-40 m long cores recovered from the Liaohe Plain and Liaodong Bay were analyzed for sedimentary characteristics, grain size, foraminifera species, and ages determined by accelerator mass spectrometry (AMS) 14C to document the stratigraphical sequence and the spatio-temporal evolution of the Liaohe Delta. Our results revealed that the sedimentary environments have evolved from fluvial, tidal flat/estuarine, to neritic and finally to a deltaic environment since the Late Pleistocene. The Holocene transgression arrived at the present coastline at ∼8500 cal a BP and flooded the maximum area of land at ∼7000 cal a BP. A deltaic environment prevailed in this area after 7000 cal a BP. Bounded by the modern Liaohe River mouth, the present deltaic sedimentary system can be divided into the eastern and western components. The rate of seaward progradation of the eastern paleocoastline was estimated to be ∼8.6 m/a since 7000 cal a BP; the eastern cores in the present coastline began receiving the deltaic sediments at ∼5000 cal a BP. The rate of seaward progradation of the western paleocoastline was estimated to be only ∼2.8 m/a since 7000 cal a BP. The coastline on the western side began accumulating deltaic sediments about 2000 years later than the eastern coastline. Depocenter shifting was hypothesized to be the reason for the spatial differences in the sedimentary processes. However, the change of sediment fluxes of the western rivers due to climate changes and ancient human impacts might be the reason for the differences of the temporal evolution of the eastern and western sedimentary systems in the Liaohe Delta.

Experimental investigation of channel avulsion frequency on river deltas under rising sea levels

NASA Astrophysics Data System (ADS)

Silvestre, J.; Chadwick, A. J.; Steele, S.; Lamb, M. P.

2017-12-01

River deltas are low-relief landscapes that are socioeconomically important; they are home to over half a billion people worldwide. Many deltas are built by cycles of lobe growth punctuated by abrupt channel shifts, or avulsions, which often reoccur at a similar location and with a regular frequency. Previous experimental work has investigated the effect of hydrodynamic backwater in controlling channel avulsion location and timing on deltas under constant sea level conditions, but it is unclear how sea-level rise impacts avulsion dynamics. We present results from a flume experiment designed to isolate the role of relative sea-level rise on the evolution of a backwater-influenced delta. The experiment was conducted in the river-ocean facility at Caltech, where a 7m long, 14cm wide alluvial river drains into a 6m by 3m "ocean" basin. The experimental delta grew under subcritical flow, a persistent backwater zone, and a range of sea level rise rates. Without sea level rise, lobe progradation produced in-channel aggradation and periodic avulsions every 3.6 ± 0.9 hours, which corresponded to when channels aggraded to approximately one-half of their flow depth. With a modest rate of sea-level rise (0.25 mm/hr), we observed enhanced aggradation in the backwater zone, causing channels to aggrade more quickly and avulse more frequently (every 2.1 ± 0.6 hours). In future work, we expect further increases in the rate of relative sea-level rise to cause avulsion frequency to decrease as the delta drowns and the backwater zone retreats upstream. Experimental results can serve as tests of numerical models that are needed for hazard mitigation and coastal sustainability efforts on drowning deltas.

Study on Spatio-Temporal Change of Ecological Land in Yellow River Delta Based on RS&GIS

NASA Astrophysics Data System (ADS)

An, GuoQiang

2018-06-01

The temporal and spatial variation of ecological land use and its current distribution were studied to provide reference for the protection of original ecological land and ecological environment in the Yellow River Delta. Using RS colour synthesis, supervised classification, unsupervised classification, vegetation index and other methods to monitor the impact of human activities on the original ecological land in the past 30 years; using GIS technology to analyse the statistical data and construct the model of original ecological land area index to study the ecological land distribution status. The results show that the boundary of original ecological land in the Yellow River Delta had been pushed toward the coastline at an average speed of 0.8km per year due to human activities. In the past 20 years, a large amount of original ecological land gradually transformed into artificial ecological land. In view of the evolution and status of ecological land in the Yellow River Delta, related local departments should adopt differentiated and focused protection measures to protect the ecological land of the Yellow River Delta.

A brief history and summary of the effects of river engineering and dams on the Mississippi River system and delta

USGS Publications Warehouse

Alexander, Jason S.; Wilson, Richard C.; Green, W. Reed

2012-01-01

The U.S. Geological Survey Forecast Mekong project is providing technical assistance and information to aid management decisions and build science capacity of institutions in the Mekong River Basin. A component of this effort is to produce a synthesis of the effects of dams and other engineering structures on large-river hydrology, sediment transport, geomorphology, ecology, water quality, and deltaic systems. The Mississippi River Basin (MRB) of the United States was used as the backdrop and context for this synthesis because it is a continental scale river system with a total annual water discharge proportional to the Mekong River, has been highly engineered over the past two centuries, and the effects of engineering have been widely studied and documented by scientists and engineers. The MRB is controlled and regulated by dams and river-engineering structures. These modifications have resulted in multiple benefits including navigation, flood control, hydropower, bank stabilization, and recreation. Dams and other river-engineering structures in the MRB have afforded the United States substantial socioeconomic benefits; however, these benefits also have transformed the hydrologic, sediment transport, geomorphic, water-quality, and ecologic characteristics of the river and its delta. Large dams on the middle Missouri River have substantially reduced the magnitude of peak floods, increased base discharges, and reduced the overall variability of intraannual discharges. The extensive system of levees and wing dikes throughout the MRB, although providing protection from intermediate magnitude floods, have reduced overall channel capacity and increased flood stage by up to 4 meters for higher magnitude floods. Prior to major river engineering, the estimated average annual sediment yield of the Mississippi River Basin was approximately 400 million metric tons. The construction of large main-channel reservoirs on the Missouri and Arkansas Rivers, sedimentation in dike

An application of remotely derived climatological fields for risk assessment of vector-borne diseases : a spatial study of filariasis prevalence in the Nile Delta, Egypt.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crombie, M. K.; Gillies, R. R.; Arvidson, R. E.

1999-12-01

This paper applies a relatively straightforward remote sensing method that is commonly used to derive climatological variables. Measurements of surface reflectance and surface radiant temperature derived from Landsat Thematic Mapper data were used to create maps of fractional vegetation and surface soil moisture availability for the southern Nile delta in Egypt. These climatological variables were subsequently used to investigate the spatial distribution of the vector borne disease Bancroftian filariasis in the Nile delta where it is focally endemic and a growing problem. Averaged surface soil moisture values, computed for a 5-km border area around affected villages, were compared to filariasismore » prevalence rates. Prevalence rates were found to be negligible below a critical soil moisture value of 0.2, presumably because of a lack of appropriate breeding sites for the Culex Pipiens mosquito species. With appropriate modifications to account for local conditions and vector species, this approach should be useful as a means to map, predict, and control insect vector-borne diseases that critically depend on wet areas for propagation. This type of analysis may help governments and health agencies that are involved in filariasis control to better focus limited resources to identifiable high-risk areas.« less

N Isotopes in Nile Sediments (ethiopia, Sudan)

NASA Astrophysics Data System (ADS)

Padoan, M.; Villa, I. M.; Garzanti, E.; Galbusera, M.; Quistini, S.; Peruta, L.; El Kammar, A.

2009-04-01

The Nile is the most important river of the Eastern Mediterranean. Its water and sediment fluxes have greatly influenced marine circulation throughout the Quaternary, and are widely considered as possible causes for stagnation and formation of sapropel (Krom et al., 1999a; 2002; Talbot et al., 2000; Freydier et al., 2001; Weldeab et al., 2002; Scrivner et al., 2004). Variations in annual flooding and baseflow of the river Nile, controlled by climate changes, had major impact on the rise and demise of Egyptian dynasties (Stanley et al., 2003). In order to better define sedimentary sources of the Nile system and to obtain more robust results, we have analyzed Nd isotopes in sediments of all its major Sudanese and Ethiopian tributaries (Atbara, Gash, Abay, Didesa, Dabus, White Nile, Bahr Ez Zeraf) in several replicate samples. Analyses were carried out on distinct mud and sand fractions (<40 microns and 125-180 microns) of 30 samples, and systematic changes related to grain size and hydraulic-sorting processes could thus be investigated. On the same samples, companion studies are being carried out on Sr isotopes (Padoan et al., 2007) and on Pb isotopes at the Geological Survey of Israel (Harlavan et al., in preparation). Overall, isotopic signals are markedly different between the White Nile system, derived from largely Archean to Paleoproterozoic basement rocks, and Ethiopian tributaries, derived in diverse proportions from largely Neoproterozoic rift-shoulder basements and overlying Oligocene flood basalts. Isotopic signals of Main Nile sediments downstream of the Atbara confluence are close to those of Blue Nile sediments, indicating that detritus is mainly provided by the latter (Garzanti et al., 2006). In the White Nile branch, the 143Nd/144Nd ratio of the mud fraction is lower in the Bahr Ez Zeraf (0.51167) than in the White Nile downstrean of the Sobat confluence (0.51219), revealing significant sediment influx from the latter. In Blue Nile and Atbara branches

Sediment consolidation settlement of Chengbei Sea area in the northern Huanghe River subaqueous delta, China

NASA Astrophysics Data System (ADS)

Liu, Jie; Feng, Xiuli; Liu, Xiao

2017-05-01

One of the most important factors controlling the morphology of the modern Huanghe (Yellow) River delta is consolidation settlement, which is impacted by fast deposition, high water content, and low density of seafloor sediment. Consolidation settlement of the Huanghe River subaqueous delta was studied based on field data, laboratory experiments on 12 drill holes, and the one-dimensional consolidation theory. Results show that vertical sediment characteristics varied greatly in the rapidly forming sedimentary bodies of the modern Huanghe River subaqueous delta. Sediments in the upper parts of drill holes were coarser than those in the deeper parts, and other physical and mechanical properties changed accordingly. On the basis of the one-dimensional consolidation theory and drilling depth, the final consolidation settlement of drill holes was between 0.6 m and 2.8 m, and the mean settlement of unit depth was at 1.5-3.5 cm/m. It takes about 15-20 years for the consolidation degree to reach 90% and the average sedimentation rate within the overlying 50 m strata was at 5 cm/a to 12 cm/a. This study helps to forecast the final consolidation settlement and settlement rate of the modern Huanghe River subaqueous delta, which provides key geotechnical information for marine engineers.

Management needs assessment for the Copper River Delta, Alaska.

Treesearch

L.E. Kruger; C.B. Tyler

1995-01-01

This report assesses needs, problems, and perceptions relevant to management for the Copper River Delta (Alaska)—the largest coastal wetland on the Pacific coast of North America. The assessment provides a basis for planning and decisionmaking and a framework for ongoing research, development, and application. It also underscores concerns about human impacts...

Trends and driving mechanism of land-use change in metropolitan areas of Pearl River Delta

NASA Astrophysics Data System (ADS)

Chen, Feng-gui; Zhang, Hong-ou; Wang, Juan; Wu, Qi-tao

2008-10-01

Taking Pearl River Delta for an example this study focuses on the trends and the driving mechanism of land-use changes in metropolises, in order to achieve the fundamental objectives of LUCC study increasing the awareness on dynamics of global land-use and land-cover changes, and improving the ability of forecasting LUCC. By analyzing the land-use change in Pearl River Delta from 1996 to 2006, it is found that the differences among internal space are notable. By establishing time-sequence-curve with SPSS software, it is shown that trends of land-use change are very clear. With factor analysis on land-use change, the study summarizes four factors of driving mechanism, including factors of economic development level, regional industrial structure, demographic and agricultural structure adjustment, which impact land change in Pearl River Delta to a different extent.

Human impact on sediment fluxes within the Blue Nile and Atbara River basins

NASA Astrophysics Data System (ADS)

Balthazar, Vincent; Vanacker, Veerle; Girma, Atkilt; Poesen, Jean; Golla, Semunesh

2013-01-01

A regional assessment of the spatial variability in sediment yields allows filling the gap between detailed, process-based understanding of erosion at field scale and empirical sediment flux models at global scale. In this paper, we focus on the intrabasin variability in sediment yield within the Blue Nile and Atbara basins as biophysical and anthropogenic factors are presumably acting together to accelerate soil erosion. The Blue Nile and Atbara River systems are characterized by an important spatial variability in sediment fluxes, with area-specific sediment yield (SSY) values ranging between 4 and 4935 t/km2/y. Statistical analyses show that 41% of the observed variation in SSY can be explained by remote sensing proxy data of surface vegetation cover, rainfall intensity, mean annual temperature, and human impact. The comparison of a locally adapted regression model with global predictive sediment flux models indicates that global flux models such as the ART and BQART models are less suited to capture the spatial variability in area-specific sediment yields (SSY), but they are very efficient to predict absolute sediment yields (SY). We developed a modified version of the BQART model that estimates the human influence on sediment yield based on a high resolution composite measure of local human impact (human footprint index) instead of countrywide estimates of GNP/capita. Our modified version of the BQART is able to explain 80% of the observed variation in SY for the Blue Nile and Atbara basins and thereby performs only slightly less than locally adapted regression models.

Tidal impacts on the subtidal flow division at the main bifurcation in the Yangtze River Delta

NASA Astrophysics Data System (ADS)

Zhang, Wei; Feng, Haochuan; Hoitink, A. J. F.; Zhu, Yuliang; Gong, Fei; Zheng, Jinhai

2017-09-01

Flow division at bifurcations in the Yangtze Estuary has received ample attention, since it may control the pathways of terrestrial sediments over downstream river branches including the 12.5 m Deepwater Navigation channel. While some efforts have been made to interpret flow division at the bifurcations of the Yangtze Estuary, little attention has been paid to the role of tides. Flow division at estuarine bifurcations is made complicated by tides that propagate from the outlet of the tidal channels into the delta. To quantify the tidal influence on the distribution of river discharge, and more generally, to understand the mechanisms governing the subtidal flow division at the tidally affected bifurcation in the Yangtze River Delta, a two-dimensional hydrodynamic model is employed. In this model, the landward boundary is chosen beyond the tidal limit, where the tidal motion has faded out entirely. The seaward boundary is chosen such that the river discharge does not influence the water level. Subtidal discharges are decomposed using the method of factor separation, to distinguish between the effects of tides, river discharge and river-tide interactions on the subtidal flow division. Results indicate that tides modify the river discharge distribution over distributary channels in the Yangtze River Delta, particularly in the dry season. A significant difference in the subtidal flow division during spring tide and neap tide shows that the tidally averaged flow division over the distributaries in the delta greatly depends on tidal amplitude. By varying the river discharge at the landward boundary and amplitudes and phases of the principal tidal constituents at the seaward boundary of the established model, the sensitivities of the subtidal flow division to the river discharge and tidal amplitude variation were investigated in detail. Generally, the tidal impacts on the subtidal flow division are around 12% to 22%, with river discharge varying from 30,000 m3s-1 to 20

Variance in Dominant Grain Size Across the Mississippi River Delta

NASA Astrophysics Data System (ADS)

Miller, K. L.; Chamberlain, E. L.; Esposito, C. R.; Wagner, R. W.; Mohrig, D. C.

2016-02-01

Proposals to restore coastal Louisiana often center on Mississippi River diversion projects wherein water and sediment are routed into wetlands and shallow waters in an effort to build land. Successful design and implementation of diversions will include consideration of behavior and characteristics of sediment, both in the river and in the receiving basin. The Mississippi River sediment load is primarily mud (roughly 75%), with the remainder being very-fine to medium sand or organic detritus. The dominance of muds leads many to suggest that diversions should focus on capturing the mud fraction despite the smaller size and longer settling times required for these particles compared to sand; others believe that sand should be the focus. We present a systemic analysis of the texture of land-building sediment in the Mississippi Delta using borehole data from various depositional environments representing a range of spatial scales, system ages, and fluvial and basin characteristics. We include subdelta-scale data from the incipient Wax Lake Delta and from the distal plain of the abandoned Lafourche subdelta, as well as crevasse-scale data from modern Cubit's Gap and the Attakapas splay, an inland Lafourche crevasse. Comparison of these sites demonstrates a large variance in the volumetric mud to sand ratios across the system. We consider the differences to be emblematic of the various forcings on each lobe as it formed and suggest that the most efficient building block for a diversion is a function of the receiving basin and is not uniform across the entire delta.

Congruent Bifurcation Angles in River Delta and Tributary Channel Networks

NASA Astrophysics Data System (ADS)

Coffey, Thomas S.; Shaw, John B.

2017-11-01

We show that distributary channels on river deltas exhibit a mean bifurcation angle that can be understood using theory developed in tributary channel networks. In certain cases, tributary network bifurcation geometries have been demonstrated to be controlled by diffusive groundwater flow feeding incipient bifurcations, producing a characteristic angle of 72∘. We measured 25 unique distributary bifurcations in an experimental delta and 197 bifurcations in 10 natural deltas, yielding a mean angle of 70.4∘±2.6∘ (95% confidence interval) for field-scale deltas and a mean angle of 68.3∘±8.7∘ for the experimental delta, consistent with this theoretical prediction. The bifurcation angle holds for small scales relative to channel width length scales. Furthermore, the experimental data show that the mean angle is 72∘ immediately after bifurcation initiation and remains relatively constant over significant time scales. Although distributary networks do not mirror tributary networks perfectly, the similar control and expression of bifurcation angles suggests that additional morphodynamic insight may be gained from further comparative study.

Distribution and condition of larval and juvenile Lost River and shortnose suckers in the Williamson River Delta restoration project and Upper Klamath Lake, Oregon

USGS Publications Warehouse

Burdick, Summer M.

2012-01-01

Federally endangered Lost River sucker (Deltistes luxatus) and shortnose sucker (Chasmistes brevirostris) were once abundant throughout their range but populations have declined. They were extirpated from several lakes in the 1920s and may no longer reproduce in other lakes. Poor recruitment to the adult spawning populations is one of several reasons cited for the decline and lack of recovery of these species and may be the consequence of high mortality during juvenile life stages. High larval and juvenile sucker mortality may be exacerbated by an insufficient quantity of suitable or high-quality rearing habitat. In addition, larval suckers may be swept downstream from suitable rearing areas in Upper Klamath Lake into Keno Reservoir, where they are assumed lost to Upper Klamath Lake populations. The Nature Conservancy flooded about 3,600 acres (1,456 hectares) to the north of the Williamson River mouth (Tulana) in October 2007, and about 1,400 acres (567 hectares) to the south and east of the Williamson River mouth (Goose Bay Farms) in October 2008, in order to retain larval suckers in Upper Klamath Lake, create nursery habitat, and improve water quality. The U.S. Geological Survey joined a long-term research and monitoring program in collaboration with The Nature Conservancy, the Bureau of Reclamation, and Oregon State University in 2008 to assess the effects of the Williamson River Delta restoration on the early life-history stages of Lost River and shortnose suckers. The primary objectives of the research were to describe habitat colonization and use by larval and juvenile suckers and non-sucker fishes and to evaluate the effects of the restored habitat on the health and condition of juvenile suckers. This report summarizes data collected in 2010 by the U.S. Geological Survey as a part of this monitoring effort and follows two annual reports on data collected in 2008 and 2009. Restoration modifications made to the Williamson River Delta appeared to provide

Morphodynamics of an eroding beach and foredune in the Mekong River delta: Implications for deltaic shoreline change

NASA Astrophysics Data System (ADS)

Anthony, E. J.; Dussouillez, P.; Dolique, F.; Besset, M.; Brunier, G.; Nguyen, V. L.; Goichot, M.

2017-09-01

River delta shorelines composed of sand may be characterized by complex spatial and temporal patterns of erosion and accretion even when sand supply is readily available. This is especially the case for deltas with multiple mouths subject to significant wave and tide influence. High-resolution topographical and wave and current measurements were conducted from 2010 to 2012 at Ba Dông beach, a popular resort located on the largest of the multiple inter-distributary plains of the Mekong River delta. Ba Dông beach is a mesotidal, multiple bar-trough system. The upper beach corresponds to the current active beach ridge in the sequence of ridges that have marked the progradation of the inter-distributary delta plains, and is capped by a low foredune that protects villages and agricultural land from marine flooding. During the low river-flow season, the beach is characterized by Northeast monsoon waves and strong longshore currents that transport sediment towards the southwest. Weaker longshore currents towards the northeast are generated by Southwest monsoon waves during the high river-flow season. Ba Dông beach underwent strong erosion between 2010 and 2012, following a phase of massive accretion. In 2012, this erosion resulted in breaching of the foredune, contributing to concerns that the Mekong delta had become vulnerable to retreat. The local erosion at Ba Dông needs to be considered, however, in the broader context of delta shoreline morphodynamics, which involves space- and time-varying patterns of beach accretion and erosion. These patterns are the present expressions of plan-view beach-ridge morphology in the delta, which is characterized by flaring and truncations that reflect changing beach morphodynamics in the course of deltaic progradation. We surmise that these patterns are related to complex interactions involving river water and sediment discharge, waves and wave-generated longshore currents, tidal currents, and shoreline orientation.

Source and migration of dissolved manganese in the Central Nile Delta Aquifer, Egypt

NASA Astrophysics Data System (ADS)

Bennett, P. C.; El Shishtawy, A. M.; Sharp, J. M.; Atwia, M. G.

2014-08-01

Dissolved metals in waters in shallow deltaic sediments are one of the world's major health problems, and a prime example is arsenic contamination in Bangladesh. The Central Nile Delta Aquifer, a drinking water source for more than 6 million people, can have high concentrations of dissolved manganese (Mn). Standard hydrochemical analyses coupled with sequential chemical extraction is used to identify the source of the Mn and to identify the probable cause of the contamination. Fifty-nine municipal supply wells were sampled and the results compared with published data for groundwaters and surface waters. Drill cuttings from 4 wells were collected and analyzed by sequential chemical extraction to test the hypothesized Mn-generating processes. The data from this research show that the Mn source is not deep saline water, microbial reduction of Mn oxides at the production depth, or leakage from irrigation drainage ditches. Instead, Mn associated with carbonate minerals in the surficial confining layer and transported down along the disturbed well annulus of the municipal supply wells is the likely source. This analysis provides a basis for future hydrogeological and contaminant transport modeling as well as remediation-modification of well completion practices and pumping schedules to mitigate the problem.

[Shifting path of industrial pollution gravity centers and its driving mechanism in Pan-Yangtze River Delta].

PubMed

Zhao, Hai-Xia; Jiang, Xiao-Wei; Cui, Jian-Xin

2014-11-01

Shifting path of industrial pollution gravity centers is the response of environmental special formation during the industry transfer process, in order to prove the responding of industrial pollution gravity centers to industry transfer in economically developed areas, this paper calculates the gravity centers of industrial wastewater, gas and solid patterns and reveals the shifting path and its driving mechanism, using the data of industrial pollution in the Pan-Yangtze River Delta from 2000 to 2010. The results show that the gravity center of the industrial waste in Pan-Yangtze River Delta shifts for sure in the last 10 years, and gravity center of solid waste shifts the maximum distance within the three wastes, which was 180.18 km, and shifting distances for waste gas and waste water were 109.51 km and 85.92 km respectively. Moreover, the gravity center of the industrial waste in Pan-Yangtze River Delta shifts westwards, and gravity centers of waste water, gas and solid shift for 0.40 degrees, 0.17 degrees and 0.03 degrees respectively. The shifting of industrial pollution gravity centers is driven by many factors. The rapid development of the heavy industry in Anhui and Jiangxi provinces results in the westward shifting of the pollutions. The optimization and adjustment of industrial structures in Yangtze River Delta region benefit to alleviating industrial pollution, and high-polluting industries shifted to Anhui and Jiangxi provinces promotes pollution gravity center shifting to west. While the development of massive clean enterprise, strong environmental management efforts and better environmental monitoring system slow the shifting trend of industrial pollution to the east in Yangtze River Delta. The study of industrial pollution gravity shift and its driving mechanism provides a new angle of view to analyze the relationship between economic development and environmental pollution, and also provides academic basis for synthetical management and control of

Dendroclimatology of the Slave River Delta, Northwest Territories, Canada

NASA Astrophysics Data System (ADS)

Jarvis, S.; Buhay, W. M.; Blair, D.; Tardif, J.; Bailey, D.

2004-05-01

It is well documented that changing hydrological conditions impact delta ecosystems. Such changes can also affect local inhabitants who have historical connections to the area and its resources. During the summer of 2003 a multifaceted paleo-environmental project was initiated to reconstruct the frequencies of floods and droughts in the Slave River Delta (SRD), Northwest Territories, Canada. The project goal is to forecast future hydrological and ecological conditions in the SRD in light of anticipated climate change and increasing demand on water resources. With the intent of expanding the climate history of the SRD, this particular aspect of the project will employ white spruce tree-ring chronologies constructed from six sites visited within the delta. Work is currently in progress to build a master chronology estimated to span over 300 years. In addition, a climate model for the SRD is also being developed and will be highlighted.

Stepwise morphological evolution of the active Yellow River (Huanghe) delta lobe (1976-2013): Dominant roles of riverine discharge and sediment grain size

NASA Astrophysics Data System (ADS)

Wu, Xiao; Bi, Naishuang; Xu, Jingping; Nittrouer, Jeffrey A.; Yang, Zuosheng; Saito, Yoshiki; Wang, Houjie

2017-09-01

The presently active Yellow River (Huanghe) delta lobe has been formed since 1976 when the river was artificially diverted. The process and driving forces of morphological evolution of the present delta lobe still remain unclear. Here we examined the stepwise morphological evolution of the active Yellow River delta lobe including both the subaerial and the subaqueous components, and illustrated the critical roles of riverine discharge and sediment grain size in dominating the deltaic evolution. The critical sediment loads for maintaining the delta stability were also calculated from water discharge and sediment load measured at station Lijin, the last gauging station approximately 100 km upstream from the river mouth. The results indicated that the development of active delta lobe including both subaerial and subaqueous components has experienced four sequential stages. During the first stage (1976-1981) after the channel migration, the unchannelized river flow enhanced deposition within the channel and floodplain between Lijin station and the river mouth. Therefore, the critical sediment supply calculated by the river inputs obtained from station Lijin was the highest. However, the actual sediment load at this stage (0.84 Gt/yr) was more than twice of the critical sediment load ( 0.35 Gt/yr) for sustaining the active subaerial area, which favored a rapid seaward progradation of the Yellow River subaerial delta. During the second stage (1981-1996), the engineering-facilitated channelized river flow and the increase in median grain size of suspended sediment delivered to the sea resulted in the critical sediment load for keeping the delta stability deceasing to 0.29 Gt/yr. The active delta lobe still gradually prograded seaward at an accretion rate of 11.9 km2/yr at this stage as the annual sediment load at Lijin station was 0.55 Gt/yr. From 1996 to 2002, the critical sediment load further decreased to 0.15 Gt/yr with the sediment grain size increased to 22.5 �

A Survey Study on Gastrointestinal Parasites of Stray Cats in Northern Region of Nile Delta, Egypt

PubMed Central

Khalafalla, Reda E.

2011-01-01

A survey study on gastrointestinal parasites in 113 faecal samples from stray cats collected randomly from Kafrelsheikh province, northern region of Nile delta of Egypt; was conducted in the period between January and May 2010. The overall prevalence was 91%. The results of this study reported seven helminth species: Toxocara cati (9%), Ancylostoma tubaeforme (4%), Toxascaris leonina (5%), Dipylidium caninum (5%), Capillaria spp. (3%), Taenia taeniformis (22%) and Heterophyes heterophyes (3%), four protozoal species: Toxoplasma gondii (9%), Sarcocyst spp. (1%), Isospora spp. (2%) and Giardia spp. (2%) and two arthropod species; Linguatula serrata (2%) and mites eggs (13%). The overall prevalence of intestinal parasites may continue to rise due to lack of functional veterinary clinics for cat care in Egypt. Therefore, there is a need to plan adequate control programs to diagnose, treat and control gastrointestinal parasites of companion as well as stray cats in the region. PMID:21760884

Variation in MERRA-2 aerosol optical depth over the Yangtze River Delta from 1980 to 2016

NASA Astrophysics Data System (ADS)

Sun, Enwei; Che, Huizheng; Xu, Xiaofeng; Wang, Zhenzhu; Lu, Chunsong; Gui, Ke; Zhao, Hujia; Zheng, Yu; Wang, Yaqiang; Wang, Hong; Sun, Tianze; Liang, Yuanxin; Li, Xiaopan; Sheng, Zhizhong; An, Linchang; Zhang, Xiaoye; Shi, Guangyu

2018-05-01

In this study, 765 instantaneous MERRA-2 (second Modern-Era Retrospective analysis for Research and Applications) aerosol optical depth (AOD) values at 550 nm were compared with those of a sky radiometer in Hefei (31.90° N, 117.17° E) for the different seasons from March 2007 to February 2010. The correlation coefficients (R) were 0.88, 0.83, 0.88, and 0.80 in spring, summer, autumn, and winter, respectively. The MERRA-2 AOD is also compared with MODIS Aqua AOD in the entire Yangtze River Delta, and good agreement has been obtained. The MERRA-2 AOD product was used to analyze the spatial distribution and temporal variation of the annual, seasonal and monthly means of the AOD over the Yangtze River Delta region from 1980 to 2016 (37 years). The mean values of the MERRA-2 AOD during the study period show that the AOD (between 0.45 and 0.55) in the northern area of the Yangtze River Delta was higher than that (between 0.30 and 0.45) of the southern area. The northwest part of the Yangtze River Delta had the highest mean AOD values (between 0.50 and 0.55). The AOD increased slowly in the 1980s and 1990s, followed by a rapid increase between 2001 and 2010. An AOD decrease can be seen from 2011 to 2016. The mean AOD in each month is discussed. High AOD was observed in March, April, and June, while low AOD could be seen in September, October, November, and December. Three different area types (large cities, medium-sized cities, and remote areas) had nearly the same annual AOD variation. Large cities had the highest AOD (about 0.48), while remote areas had the lowest (about 0.42). In summer, the AOD in remote areas was much lower than that in cities. The AOD variational trend over the Yangtze River Delta was studied during two periods. The increasing trend could be seen over the entire Yangtze River Delta in each month from 1980 to 2009. A decreasing trend was found all over the Yangtze River Delta in January, February, March, July, October, and November, whereas in

Mississippi River delta plain, Louisiana coast, and inner shelf Holocene geologic framework, processes, and resources

USGS Publications Warehouse

Williams, S. Jeffress; Kulp, Mark; Penland, Shea; Kindinger, Jack L.; Flocks, James G.; Buster, Noreen A.; Holmes, Charles W.

2009-01-01

Extending nearly 400 km from Sabine Pass on the Texas-Louisiana border east to the Chandeleur Islands, the Louisiana coastal zone (Fig. 11.1) along the north-central Gulf of Mexico is the southern terminus of the largest drainage basin in North America (>3.3 million km2), which includes the Mississippi River delta plain where approximately 6.2 million kilograms per year of sediment is delivered to the Gulf of Mexico (Coleman 1988). The Mississippi River, active since at least Late Jurassic time (Mann and Thomas 1968), is the main distributary channel of this drainage system and during the Holocene has constructed one of the largest delta plains in the world, larger than 30,000 km2 (Coleman and Prior 1980; Coleman 1981; Coleman et al. 1998). The subsurface geology and geomorphology of the Louisiana coastal zone reffects a complex history of regional tectonic events and fluvial, deltaic, and marine sedimentary processes affected by large sea-level fluctuations. Despite the complex geology of the north-central Gulf basin, a long history of engineering studies and Scientific research investigations (see table 11.1) has led to substantial knowledge of the geologic framework and evolution of the delta plain region (see also Bird et al., chapter 1 in this volume). Mississippi River delta plain, Louisiana coast, and inner shelf Holocene geologic framework, processes, and resources. Available from: https://www.researchgate.net/publication/262802561_Mississippi_River_delta_plain_Louisiana_coast_and_inner_shelf_Holocene_geologic_framework_processes_and_resources [accessed Sep 13, 2017].

An-integrated seismic approach to de-risk hydrocarbon accumulation for Pliocene deep marine slope channels, offshore West Nile Delta, Egypt

NASA Astrophysics Data System (ADS)

Othman, Adel A. A.; Bakr, Ali; Maher, Ali

2017-12-01

The Nile Delta basin is a hydrocarbon rich province that has hydrocarbon accumulations generated from biogenic and thermogenic source rocks and trapped in a clastic channel reservoirs ranging in age from Pliocene to Early Cretaceous. Currently, the offshore Nile Delta is the most active exploration and development province in Egypt. The main challenge of the studied area is that we have only one well in a channel system exceeds fifteen km length, where seismic reservoir characterization is used to de-risk development scenarios for the field by discriminating between gas sand, water sand and shale. Extracting the gas-charged geobody from the seismic data is magnificent input for 3D reservoir static modelling. Seismic data, being non-stationary in nature, have varying frequency content in time. Spectral decomposition analysis unravels the seismic signal into its initial constituent frequencies. Frequency decomposition of a seismic signal aims to characterize the time-dependent frequency response of subsurface rocks and reservoirs for imaging and mapping of bed thickness, geologic discontinuities and channel connectivity. Inversion feasibility study using crossplot between P-wave impedance (Ip) and S-wave impedance (Is) which derived from well logs (P-wave velocity, S-wave velocity and density) is applied to investigate which inversion type would be sufficient enough to discriminate between gas sand, water sand and shale. Integration between spectral analysis, inversion results and Ip vs. Is crossplot cutoffs help to generate 3D lithofacies cubes, which used to extract gas sand and water sand geobodies, which is extremely wonderful for constructing facies depositional static model in area with unknown facies distribution and sand connectivity. Therefore de-risking hydrocarbon accumulation and GIIP estimation for the field became more confident for drilling new development wells.

Dispersal of larval suckers at the Williamson River Delta, Upper Klamath Lake, Oregon, 2006-09

USGS Publications Warehouse

Wood, Tamara M.; Hendrixson, Heather A.; Markle, Douglas F.; Erdman, Charles S.; Burdick, Summer M.; Ellsworth, Craig M.; Buccola, Norman L.

2012-01-01

An advection/diffusion modeling approach was used to simulate the transport of larval suckers from spawning areas in the Williamson River, through the newly restored Williamson River Delta, to Upper Klamath Lake. The density simulations spanned the years of phased restoration, from 2006/2007 prior to any levee breaching, to 2008 when the northern part of the delta was reconnected to the lake, and 2009 when levees on both sides of the delta had been breached. Model simulation results from all four years were compared to field data using rank correlation. Spearman ρ correlation coefficients were usually significant and in the range 0.30 to 0.60, providing moderately strong validation of the model. The correlation coefficients varied with fish size class in a way that suggested that the model best described the distribution of smaller fish near the Williamson River channel, and larger fish away from the channel. When Lost River and shortnose/Klamath largescale suckers were simulated independently, the correlation results suggested that the model better described the transport and dispersal of the latter species. The incorporation of night-time-only drift behavior in the Williamson River channel neither improved nor degraded correlations with field data. The model showed that advection by currents is an important factor in larval dispersal.

A Holocene sedimentary record of tectonically influenced reduced channel mobility, Skokomish River delta, Washington State, USA

NASA Astrophysics Data System (ADS)

Arcos, Maria Elizabeth Martin

2012-12-01

At the Skokomish River delta in Washington State's Puget Lowland, coseismic uplift and tilting trapped the river against a valley wall, resulting in little to no channel migration for the last 1000 years. The most recent earthquake occurred before AD 780-990, based on stratigraphic evidence such as sand blows and abrupt facies changes. Since the hypothesized tilting a 5-km-long section of the river has not migrated laterally or avulsed, resulting in reduced migration and a muddy intertidal flat that is 2 km wider in the east than on the west side of Annas Bay. A ridge running perpendicular to the river may also have restricted channel mobility. The ridge may be either the surface expression of a blind thrust fault or a relict, uplifted and tilted shoreline. The uplift and tilting of the delta can be ascribed to any of three nearby active fault zones, of which the most likely, based on the orientation of deformation, is the Saddle Mountain fault zone, which produced a surface rupture 1000-1300 years ago. The delta has experienced submergence since the earthquake. A forest that colonized an uplifted part of the delta about 800-1200 years ago was later submerged by at least 1.6 m and is now a brackish-water marsh.

Cairo, Egypt as seen from STS-62

NASA Image and Video Library

1994-03-05

STS062-108-058 (4-18 March 1994) --- Cairo lies at the apex of the great delta of the Nile: the delta is marked by the strong greens of cultivated lands, Cairo by the gray sprawl along the river and the eastern delta apex as it develops in the direction of the airports and Suez. The city of El Giza lies on the west side of the Nile with the Giza pyramids in the desert just beyond the cultivated lands. Several major canals lead water to parts of the delta more distant from the Nile; generally these can be recognized as straighter, more engineered waterways. Towards the top left, the bifurcation of the Rosetta and Damietta branches of the Nile can be seen. These are the two major present-day veins of the Nile as it approaches the Mediterranean.

Environmental and eelgrass response to dike removal: Nisqually River Delta (2010–14)

USGS Publications Warehouse

Takesue, Renee K.

2016-10-03

Restoration of tidal flows to formerly diked marshland can alter land-to-sea fluxes and patterns of accumulation of terrestrial sediment and organic matter, and these tidal flows can also affect existing nearshore habitats. Dikes were removed from 308 hectares (ha) of the Nisqually National Wildlife Refuge on the Nisqually River Delta in south Puget Sound, Washington, in fall 2009 to improve habitat for wildlife, such as juvenile salmon. Ecologically important intertidal and subtidal eelgrass (Zostera marina) beds grow on the north and west margins of the delta. The goal of this study was to understand long-term changes in eelgrass habitat and their relation to dike removal. Sediment and eelgrass properties were monitored annually in May from 2010 to 2014 at two sites on the west side of the Nisqually River Delta along McAllister Creek, a spring-fed creek near two restored tidal channels. In May 2014, the mean canopy height of eelgrass was the same as in previous years in an 8-ha bed extending to the Nisqually River Delta front, but mean canopy height was 20 percent lower in a 0.3-ha eelgrass bed closer to the restored marsh when compared to mean canopy height of eelgrass in May 2010, 6 months after dike removal was completed. Over 5 years, the amount of eelgrass leaf area per square meter (m2) in the 8-ha bed increased slightly, and surface-sediment grain size became finer. In contrast, in the 0.3-ha bed, eelgrass leaf area per m2 decreased by 45 percent, and surface sediment coarsened. Other potential stressors, including sediment pore water reduction-oxidation potential (redox) and hydrogen sulfide (H2S) concentration in the eelgrass rhizosphere, or root zone, were below levels that negatively affect eelgrass growth and therefore did not appear to be environmental stressors on plants. Eelgrass biomass partitioning, though less favorable in the 8-ha eelgrass bed compared to the 0.3-ha one, was well above the critical above-ground to below-ground biomass ratio of

Dynamical modelling of river deltas on Titan and Earth

NASA Astrophysics Data System (ADS)

Witek, Piotr P.; Czechowski, Leszek

2015-01-01

The surface of Titan hosts a unique Earth-like environment with lakes and rivers, and active 'hydrologic' cycle of methane. We investigate sediment transport in Titanian rivers and deposition in Titanian lakes with particular attention to formation of river deltas. The obtained results are compared with analogous terrestrial processes. The numerical model based on Navier-Stokes equations for depth-integrated two dimensional turbulent flow and additional equations for bed-load and suspended-load sediment transport was used in our research. It is found that transport of icy grains in Titanian rivers is more effective than silicate grains of the same size in terrestrial rivers for the same assumed total discharge. This effect is explained theoretically using dimensionless form of equations or comparing forces acting on the grains. Our calculations confirm previous results (Burr et al., 2006. Icarus. 181, 235-242). We calculate also models with organic sediments of different densities, namely 1500 and 800 kg m-3. We found substantial differences between materials of varying densities on Titan, but they are less pronounced than differences between Titan and Earth.

Community-based restoration of desert wetlands: the case of the Colorado River delta

Treesearch

Osvel Hinojosa-Huerta; Mark Briggs; Yamilett Carrillo-Guerroro; Edward P. Glenn; Miriam Lara-Flores; Martha Roman-Rodriguez

2005-01-01

Wetland areas have been drastically reduced through the Pacific Flyway and the Sonoran Desert, with severe consequences for avian populations. In the Colorado River delta, wetlands have been reduced by 80 percent due to water management practices in the Colorado River basin. However, excess flows and agricultural drainage water has restored some areas, providing...

A large-scale environmental flow experiment for riparian restoration in the Colorado River delta

USGS Publications Warehouse

Shafroth, Patrick B.; Schlatter, Karen; Gomez-Sapiens, Martha; Lundgren, Erick; Grabau, Matthew R.; Ramirez-Hernandez, Jorge; Rodriguez-Burgeueno, J. Eliana; Flessa, Karl W.

2017-01-01

Managing streamflow is a widely-advocated approach to provide conditions necessary for seed germination and seedling establishment of trees in the willow family (Salicaceae). Experimental flow releases to the Colorado River delta in 2014 had a primary objective of promoting seedling establishment of Fremont cottonwood (Populus fremontii) and Goodding's willow (Salix gooddingii). We assessed seed germination and seedling establishment of these taxa as well as the non-native tamarisk (Tamarix spp.) and native seepwillow shrubs (Baccharis spp.) in the context of seedling requirements and active land management (land grading, vegetation removal) at 23 study sites along 87 river km. In the absence of associated active land management, experimental flows to the Colorado River delta were minimally successful at promoting establishment of new woody riparian seedlings, except for non-native Tamarix. Our results suggest that the primary factors contributing to low seedling establishment varied across space, but included low or no seed availability in some locations for some taxa, insufficient soil moisture availability during the growing season indicated by deep groundwater tables, and competition from adjacent vegetation (and, conversely, availability of bare ground). Active land management to create bare ground and favorable land grades contributed to significantly higher rates of Salicaceae seedling establishment in a river reach with high groundwater tables. Our results provide insights that can inform future environmental flow deliveries to the Colorado River delta and its ecosystems and other similar efforts to restore Salicaceae taxa around the world.

Chlorinated and polycyclic aromatic hydrocarbons in riverine and estuarine sediments from Pearl River Delta, China.

PubMed

Mai, Bi-Xian; Fu, Jia-Mo; Sheng, Guo-Ying; Kang, Yue-Hui; Lin, Zheng; Zhang, Gan; Min, Yu-Shuan; Zeng, Eddy Y

2002-01-01

Spatial distribution of chlorinated hydrocarbons [chlorinated pesticides (CPs) and polychlorinated biphenyls (PCBs)] and polycyclic aromatic hydrocarbons (PAHs) was measured in riverine and estuarine sediment samples from Pearl River Delta, China, collected in 1997. Concentrations of CPs of the riverine sediment samples range from 12 to 158 ng/g, dry weight, while those of PCBs range from 11 to 486 ng/g. The CPs concentrations of the estuarine sediment samples are in the range 6-1658 ng/g, while concentrations of PCBs are in the range 10-339 ng/g. Total PAH concentration ranges from 1168 to 21,329 ng/g in the riverine sediment samples, whereas the PAH concentration ranges from 323 to 14,812 ng/g in the sediment samples of the Estuary. Sediment samples of the Zhujiang River and Macao harbor around the Estuary show the highest concentrations of CPs, PCBs, and PAHs. Possible factors affecting the distribution patterns are also discussed based on the usage history of the chemicals, hydrologic condition, and land erosion due to urbanization processes. The composition of PAHs is investigated and used to assess petrogenic, combustion and naturally derived PAHs of the sediment samples of the Pearl River Delta. In addition, the concentrations of a number of organic compounds of the Pearl River Delta samples indicate that sediments of the Zhujiang river and Macao harbor are most likely to pose biological impairment.

An Emergent Bifurcation Angle on River Deltas

NASA Astrophysics Data System (ADS)

Shaw, J.; Coffey, T.

2017-12-01

Distributary channel bifurcations on river deltas are important features that control water, sediment, and nutrient routing and can dictate large-scale stratigraphic heterogeneity. We use theory originally developed for a special case of tributary networks to understand the dynamics of distributary channel bifurcations. Interestingly, bifurcations in groundwater-fed tributary networks have been shown to evolve dependent on the diffusive flow field outside the network. These networks possess a characteristic bifurcation angle of 72°, due to Laplacian flow in the groundwater flow field near tributary channel tips (gradient2h2=0, where h is water surface elevation). We develop and test the hypothesis that bifurcation angles in distributary channel networks are likewise dictated by the external flow field, in this case the shallow surface water surrounding the subaqueous portion of distributary channel bifurcations in a deltaic setting. We measured 130 unique distributary channel bifurcations in a single experimental delta and in 10 natural deltas, yielding a mean angle of 70.35°±2.59° (95% confidence interval), in line with the theoretical prediction. These data and hydrodynamic scaling arguments convince us that distributary network formation can result simply from the coupling of (Laplacian) extra-channel flow to channels along subaqueous channel networks. The simplicity of this model provides new insight into distributary network formation and its geomorphic and stratigraphic consequences.

Outbreaks of the Brown Planthopper Nilaparvata lugens (Stål) in the Yangtze River Delta: Immigration or Local Reproduction?

PubMed Central

Zhai, Bao-Ping; Lu, Ming-Hong; Liu, Wan-Cai; Zhu, Feng; Wu, Xiang-Wen; Chen, Gui-Hua; Zhang, Xiao-Xi

2014-01-01

An effective control strategy for migratory pests is difficult to implement because the cause of infestation (i.e., immigration or local reproduction) is often not established. In particular, the outbreak mechanisms of the brown planthopper, Nilaparvata lugens (Stål), an insect causing massive losses in rice fields in the Yangtze River Delta in China, are frequently unclear. Field surveys of N. lugens were performed in Jiangsu and Zhejiang Provinces in 2008 to 2010 and related historical data from 2003 onwards were collected and analyzed to clarify the cause of these infestations. Results showed that outbreaks of N. lugens in the Yangtze River Delta were mostly associated with an extremely high increase in population. Thus, reproduction rather than immigration from distant sources were the cause of the infestations. Although mass migration occurred late in the season (late August and early September), the source areas of N. lugens catches in the Yangtze River Delta were mainly located in nearby areas, including the Yangtze River Delta itself, Anhui and northern Jiangxi Provinces. These regions collectively form the lower-middle reaches of the Yangtze River, and the late migration can thus be considered as an internal bioflow within one population. PMID:24558459

Outbreaks of the brown planthopper Nilaparvata lugens (Stål) in the Yangtze River Delta: immigration or local reproduction?

PubMed

Hu, Gao; Lu, Fang; Zhai, Bao-Ping; Lu, Ming-Hong; Liu, Wan-Cai; Zhu, Feng; Wu, Xiang-Wen; Chen, Gui-Hua; Zhang, Xiao-Xi

2014-01-01

An effective control strategy for migratory pests is difficult to implement because the cause of infestation (i.e., immigration or local reproduction) is often not established. In particular, the outbreak mechanisms of the brown planthopper, Nilaparvata lugens (Stål), an insect causing massive losses in rice fields in the Yangtze River Delta in China, are frequently unclear. Field surveys of N. lugens were performed in Jiangsu and Zhejiang Provinces in 2008 to 2010 and related historical data from 2003 onwards were collected and analyzed to clarify the cause of these infestations. Results showed that outbreaks of N. lugens in the Yangtze River Delta were mostly associated with an extremely high increase in population. Thus, reproduction rather than immigration from distant sources were the cause of the infestations. Although mass migration occurred late in the season (late August and early September), the source areas of N. lugens catches in the Yangtze River Delta were mainly located in nearby areas, including the Yangtze River Delta itself, Anhui and northern Jiangxi Provinces. These regions collectively form the lower-middle reaches of the Yangtze River, and the late migration can thus be considered as an internal bioflow within one population.

Influences of Relative Sea-Level Rise and Mississippi River Delta Plain Evolution on the Holocene Middle Amite River, Southeastern Louisiana

USGS Publications Warehouse

Autin, W.J.

1993-01-01

The Holocene geomorphic history of southeastern Louisiana's middle Amite River is recorded in the stratigraphy of three alloformations, identified in decreasing age as the Watson (WAT), Denham Springs (DS), and Magnolia Bridge (MAG). The WAT meander belt formed by at least 9000 yr B.P., when sea level was lower and the Amite River was tributary to a larger ancestral drainage basin. The DS became an active meander belt by at least 3000 yr B.P., in response to relative sea-level rise and eastward progradation of the Mississippi River delta plain. The MAG developed its meander belt, in part, during the European settlement of the drainage basin, and is now attempting to adjust to modern anthropogenic influences. Geomorphic influences on the middle Amite River floodplain have temporal and spatial components that induce regional- and local-scale effects. Regional extrinsic influences caused meander belt avulsion that produced alloformations. However, local influences produced intrinsic geomorphic thresholds that modified channel morphology within a meander belt but did not induce alloformation development. Base-level influences of the relative sea-level rise and the Mississippi River delta plain were so dominant that the effects of possible climate change were not recognized in the Holocene Amite River system.

River-plume sedimentation and 210Pb/7Be seabed delivery on the Mississippi River delta front

NASA Astrophysics Data System (ADS)

Keller, Gregory; Bentley, Samuel J.; Georgiou, Ioannis Y.; Maloney, Jillian; Miner, Michael D.; Xu, Kehui

2017-06-01

To constrain the timing and processes of sediment delivery and submarine mass-wasting events spanning the last few decades on the Mississippi River delta front, multi-cores and gravity cores (0.5 and <3 m length respectively) were collected seaward of the Mississippi River Southwest Pass in 25-75 m water depth in 2014. The cores were analyzed for radionuclide activity (7Be, 210Pb, 137Cs), grain size, bulk density, and fabric (X-radiography). Core sediments are faintly bedded, sparsely bioturbated, and composed mostly of clay and fine silt. Short-term sedimentation rates (from 7Be) are 0.25-1.5 mm/day during river flooding, while longer-term accumulation rates (from 210Pb) are 1.3-7.9 cm/year. In most cores, 210Pb activity displays undulatory profiles with overall declining activity versus depth. Undulations are not associated with grain size variations, and are interpreted to represent variations in oceanic 210Pb scavenging by river-plume sediments. The 210Pb profile of one gravity core from a mudflow gully displays uniform basal excess activity over a zone of low and uniform bulk density, interpreted to be a mass-failure event that occurred 9-18 years before core collection. Spatial trends in sediment deposition (from 7Be) and accumulation (from 210Pb) indicate that proximity to the river mouth has stronger influence than local facies (mudflow gully, depositional lobe, prodelta) over the timeframe and seabed depth represented by the cores (<40 years, <3 m length). This may be explained by rapid proximal sediment deposition from river plumes coupled with infrequent tropical cyclone activity near the delta in the last 7 years (2006-2013), and by the location of most sediment failure surfaces (from mass flows indicated by parallel geophysical studies) deeper than the core-sampling depths of the present study.

2500 years of changing shoreline accretion rates at the mouths of the Mekong River delta

NASA Astrophysics Data System (ADS)

Besset, Manon; Tamura, Toru; Anthony, Edward; Brunier, Guillaume; Saito, Yoshiki; Dussouillez, Philippe; Lap Nguyen, Van; Ta, Oahn

2016-04-01

The Mekong River delta prograded rapidly in a relatively sheltered bight in the South China Sea under the influence of high fluvial sediment supply 5300 to 3500 years ago, developing from an estuary into a delta. This >200 km seaward growth resulted in increasing exposure of the delta to ocean waves that led to a more wave-influenced mode of progradation characterized by the construction of numerous sets of beach ridges in the eastern sector of the delta, which shows a system of multiple distributary mouths. The growth pattern of this river-mouth sector over the last 2500 years has been determined from OSL dating of these beach-ridge deposits, while the most up-to-date trends (1950-2014) have been highlighted from the analysis of maps and satellite images. The OSL ages show that the area of the delta in the mouths sector remained nearly constant till about 500 yr BP, following which significant accretion occurred, possibly in response to changes in catchment land-use and monsoon rainfall and attendant river water and sediment discharge. A fine-tuned analysis of changes since 1950 shows dominant but fluctuating accretion, with two periods of erosion. The first (1965-1973) occurred in the course of the second Indochina war, and the second more recently from 2003 to 2011, followed by mild recovery between 2011 and 2014. These fluctuations most likely reflect changes in sediment supply caused by the vicissitudes of war and its effect on vegetation cover, as well as variations in monsoon rainfall and discharge, and, for the most recent period, massive sand mining in the river and deltaic channels. Accretion of the mouths sector has gone apace, over the same recent multi-decadal period, with large-scale erosion of the muddy shores of the delta in the western South China Sea and the Gulf of Thailand, thus suggesting that the mouths sector may be increasingly sequestering sediment to the detriment of the rest of the delta shoreline. The accretion in the mouths sector is

It takes more than water: Restoring the Colorado River Delta

USGS Publications Warehouse

Pitt, Jennifer; Kendy, Eloise; Schlatter, Karen; Hinojosa-Huertaf, Osvel; Flessa, Karl W.; Shafroth, Patrick B.; Ramirez-Hernandez, Jorge; Nagler, Pamela L.; Glenn, Edward P.

2017-01-01

Environmental flows have become important tools for restoring rivers and associated riparian ecosystems (Arthington, 2012; Glenn et al., 2017). In March 2014, the United States and Mexico initiated a bold effort in restoration, delivering from Morelos Dam a “pulse flow” of water into the Colorado River in its delta for the purpose of learning about its environmental effects (Flessa et al., 2013; Bark et al., 2016). Specifically, scientists evaluated whether the pulse flow, albeit miniscule compared to historical floods, could provide the ecological functions needed to establish native, flood-dependent vegetation to restore natural habitat along the riparian corridor.

A Comparative Study Environmental and Radiological Causes Of Cancer In River Nile State, Sudan

NASA Astrophysics Data System (ADS)

Hamid, Eyad; Khair, Hatim

The causes of cancer in River Nile state are differ between environmental and radiological, this paper tried to make comparison between the two causes, to determine the real cause behind the large rising of cancer cases in this state, considering the daily habits for the patients and the possible contamination in the natural resources around them. The noticeable thing that most of cancer cases are might be due to the high concentration of nitrate pollutant detected in natural resources such as drinking water; also by looking to the radioactive elements we see there's high concentration of some radioactive elements specially the K-40 which found in Portulaca Oleracea.

Biogeochemical features of aquatic plants in the Selenga River delta

NASA Astrophysics Data System (ADS)

Shinkareva, Galina; Lychagin, Mikhail

2014-05-01

The Selenga River system provides more than a half of the Lake Baikal total inflow. The river collects a significant amount of pollutants (e.g. heavy metals) from the whole basin. These substances are partially deposited within the Selenga delta, and partially are transported further to the lake. A generous amount of aquatic plants grow in the delta area according to its favorable conditions. This vegetation works as a specific biofilter. It accumulates suspended particles and sorbs some heavy metals from the water. The study aimed to reveal the species of macrophytes which could be mostly important for biomonitoring according to their chemical composition. The field campaign took place in the Selenga River delta in July-August of 2011 (high water period) and in June of 2012 (low water period). 14 species of aquatic plants were collected: water starwort Callitriche hermaphroditica, small yellow pond lily Nuphar pumila, pondweeds Potamogeton crispus, P. pectinatus, P. friesii, broadleaf cattail Typha latifolia, hornwort or coontail Ceratophyllum demersum, arrowhead Sagittaria natans, flowering rush (or grass rush) Butomus umbellatus, reed Phragmites australis, parrot's feather Myriophyllum spicatum, the common mare's tail Hippuris vulgaris, Batrachium trichophyllum, canadian waterweed Elodea canadensis. The samples were dried, grinded up and digested in a mixture of HNO3 and H2O2. The chemical composition of the plant material was defined using ICP-MS and ICP-AES methods. Concentrations of Fe, Mn, Cr, Ni, Cu, B, Zn, V, Co, As, Mo, Pb, and U were considered. The study revealed that Potamogeton pectinatus and Myriophyllum spicatum concentrate elements during both high and low water periods. Conversely the Butomus umbellatus and Phragmites australis contain small amount of heavy metals. The reed as true grasses usually accumulates fewer amounts of elements than other macrophytes. To compare biogeochemical specialization of different species we suggest to use

Mississippi River delta as seen from the Gemini 9-A spacecraft

NASA Technical Reports Server (NTRS)

1966-01-01

The Mississippi River delta, and Gulf coasts of Louisiana, Mississippi, Alabama and Florida as seen from the Gemini 9-A spacecraft during its first revolution of the earth. Florida peninsula is seen at upper right corner of picture. lake Pontchartrain is at lower left. new orleans is located between the lake and the U-shaped bend in the river. Large bay at top left center is Mobile Bay. Apalachicola, Florida, is the point of land at top center of picture. Note alluvial deposit at mouths of Mississippi.

Developing a Truly Global Delta Database to Assess Delta Morphology and Morphodynamics

NASA Astrophysics Data System (ADS)

Caldwell, R. L.; Edmonds, D. A.; Baumgardner, S. E.; Whaling, A.

2015-12-01

Delta morphology reflects the interplay of various environmental parameters, though these relationships have only been tested on small datasets with 30-50 deltas. These datasets are biased toward the largest deltas, which typically have compound morphologies, form on passive margins, and may not be representative of the full breadth in delta morphology. With the goal of building more robust predictions of delta morphology to enhance hazard mitigation and resiliency planning, we have developed a truly global delta database including every delta on the world's marine coastlines. Using Google Earth imagery, we first identified all fluvial river mouths (≥ 50 m wide) connected to an upstream catchment. Deltas are defined geomorphically as river mouths that split into two or more active or relict distributary channels, end in a depositional protrusion from the shoreline, or do both. In our database we identified 5,801 river mouths, and 1,426 of those coastal rivers (~25%) have a geomorphic delta. ~75% of deltas exhibit an active or relict distributary network, while the remaining ~25% are single channel deltas with a basinward protrusion. Preliminary morphometric analysis (ratio of shore-parallel width, W, to shore-perpendicular length, L) on a subset of 159 deltas suggests W:L values range from 0.52 (elongate) to 23.6 (broad/cuspate). The median W:L value is 2.68, suggesting the majority of deltas are roughly semi-circular (W:L = 2), and the distribution is heavily skewed to the broad/cuspate deltas (~28% are >4 times wider than they are long). Preliminary comparison to downstream significant wave height data shows that the 'wider' deltas relate to higher wave heights (R2 = 0.42), though the data are scattered. Ultimately, the database will include additional measured morphometrics, including number of channel mouths and delta area, and morphodynamic data derived from serial Landsat imagery.

Controls on delta formation, area, and topset slope: New predictive relationships developed using a global delta dataset

NASA Astrophysics Data System (ADS)

Caldwell, R. L.; Edmonds, D. A.; Baumgardner, S. E.; Paola, C.; Roy, S.; Nienhuis, J.

2017-12-01

River deltas are irreplaceable natural and societal resources, though they are at risk of drowning due to sea-level rise and decreased sediment delivery. To enhance hazard mitigation efforts in the face of global environmental change, we must understand the controls on delta growth. Previous empirical studies of delta growth are based on small datasets and often biased towards large, river-dominated deltas. We are currently lacking relationships that predict delta formation, area, or topset slope across the full breadth of global deltas. To this end, we developed a global dataset of 5,229 rivers (with and without deltas) paired with nine upstream (e.g., sediment discharge) and four downstream (e.g., wave height) environmental variables. Using Google Earth imagery, we identify all coastal river mouths (≥ 50 m wide) connected to an upstream catchment, and define deltas as river mouths that split into two or more distributary channels, end in a depositional protrusion from the shoreline, or do both. Delta area is defined as the area of the polygon connecting the delta node, two lateral shoreline extent points, and the basinward-most extent of the delta. Topset slope is calculated as the average, linear slope from the delta node elevation (extracted from SRTM data) to the main channel mouth, and shoreline and basinward extent points. Of the 5,229 rivers in our dataset, 1,816 (35%) have a delta. Using 495 rivers (those with data available for all variables), we build an empirically-derived relationship that predicts delta formation with 76% success. Delta formation is controlled predominantly by upstream water and sediment discharge, with secondary control by downstream waves and tides that suppress delta formation. For those rivers that do form deltas, we show that delta area is best predicted by sediment discharge, bathymetric slope, and drainage basin area (R2 = 0.95, n = 170), and exhibits a negative power-law relationship with topset slope (R2 = 0.85, n = 1

Assessment and potential sources of metals in the surface sediments of the Yellow River Delta, Eastern China.

PubMed

Cheng, Qingli; Lou, Guangyan; Huang, Wenhai; Li, Xudong

2017-07-01

The Yellow River Delta is the most intact estuary wetland in China and suffers from great pressure of metals. Seventy-seven surface sediment samples were collected in the delta, and contents of Cu, Pb, Cd, Cr, Zn, Ni, and Mn were analyzed by inductively coupled plasma spectrometry and those of Hg and As by atomic fluorescence spectrometry. The results showed that means of metal contents (ppm, dry weight) were as follows: Hg, 0.04; Cr, 61.72; Cu, 20.97; Zn, 60.73; As, 9.47; Pb, 21.91; Cd, 0.12; Ni, 27.24; and Mn, 540.48. 43.8% of Hg and 14.3% of Cd were from the allogenic source while others from the authigenic source. The results of the geoaccumulation indexes appeared that 6.5% of sites from the estuarine and the Gudao areas were moderately polluted by Hg. All ecological risk index values of Hg and 37.7% of Cd were more than 40, which were the main factors of strongly and moderately potential ecological risks of 37.7% of sites in the delta. High Cd contents may be due to the alkaline conditions of the delta and the unreasonable management of the farmland, while the abnormal distribution of Hg to the wet or dry deposition and the erosion of the seawater. It was suggested to monitor Hg content in the atmosphere of the Yellow River Delta. The results were expected to update the pollution status of metals in the delta and created awareness of preserving the sound condition of the Yellow River Delta.

Late Quaternary Stratigraphic Architecture of the Santee River Delta, South Carolina, U.S.A.

NASA Astrophysics Data System (ADS)

Long, J. H.; Hanebuth, T. J. J.

2017-12-01

The Santee River of South Carolina is the second largest river in terms of drainage area and discharge in the eastern United States and forms the only river-fed delta on the country's Atlantic coast. Significant anthropogenic modifications to this system date back to the early 18th century with the extensive clearing of coastal wetland forest for rice cultivation. In the 1940's the construction of large upstream dams permanently altered the discharge of the Santee River. These modifications are likely documented within the sedimentary record of the Santee Delta as episodes of major environmental changes. The Piedmont-sourced Santee River system incised its valley to an estimated depth of 20 m during lower glacial sea level. Sedimentation during the subsequent Holocene transgression and highstand has filled much of this accommodation. The Santee system remains largely under-investigated with only a handful of studies completed in the 1970's and 1980's based on sediment cores and cuttings. Through the use of high frequency seismic profiles (0.5 - 24 kHz), sediment cores, and other field data, we differentiate depositional units, architectural elements, and bounding surfaces with temporal and spatial distributions reflecting the changing morphodynamics of this complex system at multiple scales. These lithosomes are preserved within both modern inshore and offshore settings and were deposited within a range of paralic environments by processes active on fluvial/estuarine bars, floodplains, marshes, tidal flats, spits, beach ridges, and in backbarrier settings. They are bound by surfaces ranging from diastems to regional, polygenetic, low-angle and channel-form erosional surfaces. Detailed descriptions of cores taken from within the upper 6 m of the modern lower delta plain document heterolithic, mixed-energy, organic-rich, largely aggradational sedimentation dating back to at least 5 ka cal BP. Offshore, stacked, sand-rich, progradational packages sit atop heterolithic

Sediment suspension and the dynamic mechanism during storms in the Yellow River Delta.

PubMed

Bian, Shuhua; Hu, Zjian; Liu, Jianqiang; Zhu, Zichen

2016-12-01

The suspension and hydrodynamic characteristics of the Yellow River Delta during storms were analyzed based on suspended samples obtained using automatic samplers during a storm event in the Yellow River Delta. Synchronous data for winds, waves, and tides were also collected from a nearby station. The results show that under wind speeds of 5-15 m/s and wave heights of 50-150 cm, the suspended content reached 5.7-49.6 kg/m 3 , which is 10-100 times higher than that under normal weather conditions. The medium diameter of suspended particles was 1.2-2.1 μm (8.9-9.7 Φ), which was approximately 1-2 Φ finer than that under normal weather conditions. During the early stages of the measurements, the sea level had risen by 50 cm owing to the storm, which was in addition to the tidal sea level change. We suggest that during the storms, the waves strengthened and the storm-induced sea level change, which was combined with tidal currents moving in the same direction, produced high-speed currents. This overcame the cohesive forces among the fine sediment particles and suspended a large amount of sediment. As a result, the suspended content increased markedly and the suspended particle size became finer. This explains the intense siltation and erosion of the Yellow River Delta during storms.

Dispersion mechanisms of a tidal river junction in the Sacramento–San Joaquin Delta, California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gleichauf, Karla T.; Wolfram, Philip J.; Monsen, Nancy E.

In branching channel networks, such as in the Sacramento–San Joaquin River Delta, junction flow dynamics contribute to dispersion of ecologically important entities such as fish, pollutants, nutrients, salt, sediment, and phytoplankton. Flow transport through a junction largely arises from velocity phasing in the form of divergent flow between junction channels for a portion of the tidal cycle. Field observations in the Georgiana Slough junction, which is composed of the North and South Mokelumne rivers, Georgiana Slough, and the Mokelumne River, show that flow phasing differences between these rivers arise from operational, riverine, and tidal forcing. A combination of Acoustic Dopplermore » Current Profile (ADCP) boat transecting and moored ADCPs over a spring–neap tidal cycle (May to June 2012) monitored the variability of spatial and temporal velocity, respectively. Two complementary drifter studies enabled assessment of local transport through the junction to identify small-scale intrajunction dynamics. We supplemented field results with numerical simulations using the SUNTANS model to demonstrate the importance of phasing offsets for junction transport and dispersion. Different phasing of inflows to the junction resulted in scalar patchiness that is characteristic of MacVean and Stacey’s (2011) advective tidal trapping. Furthermore, we observed small-scale junction flow features including a recirculation zone and shear layer, which play an important role in intra-junction mixing over time scales shorter than the tidal cycle (i.e., super-tidal time scales). Thus, the study period spanned open- and closed-gate operations at the Delta Cross Channel. Synthesis of field observations and modeling efforts suggest that management operations related to the Delta Cross Channel can strongly affect transport in the Delta by modifying the relative contributions of tidal and riverine flows, thereby changing the junction flow phasing.« less

Dispersion mechanisms of a tidal river junction in the Sacramento–San Joaquin Delta, California

DOE PAGES

Gleichauf, Karla T.; Wolfram, Philip J.; Monsen, Nancy E.; ...

2014-12-17

In branching channel networks, such as in the Sacramento–San Joaquin River Delta, junction flow dynamics contribute to dispersion of ecologically important entities such as fish, pollutants, nutrients, salt, sediment, and phytoplankton. Flow transport through a junction largely arises from velocity phasing in the form of divergent flow between junction channels for a portion of the tidal cycle. Field observations in the Georgiana Slough junction, which is composed of the North and South Mokelumne rivers, Georgiana Slough, and the Mokelumne River, show that flow phasing differences between these rivers arise from operational, riverine, and tidal forcing. A combination of Acoustic Dopplermore » Current Profile (ADCP) boat transecting and moored ADCPs over a spring–neap tidal cycle (May to June 2012) monitored the variability of spatial and temporal velocity, respectively. Two complementary drifter studies enabled assessment of local transport through the junction to identify small-scale intrajunction dynamics. We supplemented field results with numerical simulations using the SUNTANS model to demonstrate the importance of phasing offsets for junction transport and dispersion. Different phasing of inflows to the junction resulted in scalar patchiness that is characteristic of MacVean and Stacey’s (2011) advective tidal trapping. Furthermore, we observed small-scale junction flow features including a recirculation zone and shear layer, which play an important role in intra-junction mixing over time scales shorter than the tidal cycle (i.e., super-tidal time scales). Thus, the study period spanned open- and closed-gate operations at the Delta Cross Channel. Synthesis of field observations and modeling efforts suggest that management operations related to the Delta Cross Channel can strongly affect transport in the Delta by modifying the relative contributions of tidal and riverine flows, thereby changing the junction flow phasing.« less

Sediment transport dynamics linked to morphological evolution of the Selenga River delta, Lake Baikal, Russia

NASA Astrophysics Data System (ADS)

Dong, T. Y.; Nittrouer, J.; McElroy, B. J.; Czapiga, M. J.; Il'icheva, E.; Pavolv, M.; Parker, G.

2014-12-01

The Selenga River delta, Lake Baikal, Russia, is approximately 700 km2 in size and contains three active lobes that receive varying amounts of water and sediment discharge. This delta represents a unique end-member in so far that the system is positioned along the deep-water (~1500 m) margin of Lake Baikal and therefore exists as a shelf-edge delta. In order to evaluate the morphological dynamics of the Selenga delta, field expeditions were undertaken during July 2013 and 2014, to investigate the morphologic, sedimentologic, and hydraulic nature of this delta system. Single-beam bathymetry data, sidescan sonar data, sediment samples, and aerial survey data were collected and analyzed to constrain: 1) channel geometries within the delta, 2) bedform sizes and spatial distributions, 3) grain size composition of channel bed sediment as well as bank sediment, collected from both major and minor distributary channels, and 4) elevation range of the subaerial portion of the delta. Our data indicate that the delta possesses downstream sediment fining, ranging from predominantly gravel and sand near the delta apex to silt and sand at the delta-lake interface. Field surveys also indicate that the Selenga delta has both eroding and aggrading banks, and that the delta is actively incising into some banks that consist of terraces, which are defined as regions that are not inundated by typical 2- to 4-year flood discharge events. Therefore the terraces are distinct from the actively accreting regions of the delta that receive sedimentation via water inundation during regular river floods. We spatially constrain the regions of the Selenga delta that are inundated during floods versus terraced using a 1-D water-surface hydrodynamic model that produces estimates of stage for flood water discharges, whereby local water surface elevations produced with the model are compared to the measured terrestrial elevations. Our analyses show that terrace elevations steadily decrease downstream

Geomorphology of the Chippewa River delta of Glacial Lake Saginaw, central Lower Michigan, USA

NASA Astrophysics Data System (ADS)

Connallon, Christopher B.; Schaetzl, Randall J.

2017-08-01

We introduce, characterize, and interpret the geomorphic history of a relict, Pleistocene-aged delta of the Chippewa River in central Lower Michigan. The broad, sandy Chippewa delta developed into various stages of Glacial Lake Saginaw, between ca. ≈ 17 and 15 ka·BP (calibrated ages). Although the delta was first identified in 1955 on a statewide glacial geology map, neither its extent nor its Pleistocene history had been previously determined. The delta is typically forested, owing to its wet, sandy soils, which stand out against the agricultural fields of the surrounding, loamy lake plain sediments. The delta heads near the city of Mt Pleasant and extends eastward onto the Saginaw Lowlands, i.e., the plain of Glacial Lake Saginaw. Data from 3285 water well logs, 180 hand augered sites, and 185 points randomly located in a GIS on two-storied (sand over loam) soils were used to determine the extent, textural properties, and thickness of the delta. The delta is ≈ 18 km wide and ≈ 38 km long and is sandy throughout. Deltaic sediments from neighboring rivers that also drained into Glacial Lake Saginaw merge with the lower Chippewa delta, obscuring its boundary there. The delta is thickest near the delta's head and in the center, but thins to 1-2 m or less on its eastern margins. Mean thicknesses are 2.3-2.9 m, suggestive of a thin sediment body, frequently impacted by the waves and fluctuating waters of the lakes. Although beach ridges are only weakly expressed across the delta because of the sandy sediment, the coarsest parts of the delta are generally coincident with some of these inferred former shorezones and have a broad, incised channel that formed while lake levels were low. The thick upper delta generally lies above the relict shorelines of Glacial Lakes Saginaw and Arkona (≈ 17.1 to ≈ 16 ka·BP), whereas most of the thin, distal delta is associated with Glacial Lake Warren (≈ 15 ka·BP). Together, these data suggest that the Chippewa delta formed

Conflicts of Shared Resources: A Case Study of River Nile

DTIC Science & Technology

2012-03-22

as Lake Kivu. Rwanda joined the earlier Nile basin project, Hydromet , in 1967, with the support on the UNDP. 18 Although the country does not...operation Hydromet . In 1967, with the assistance of the United Nations Development Program (UNDP) and the World Meteorological Organization (WMO), Egypt...Kenya, Sudan, Tanzania and Uganda launched the Hydromet Survey project to regulate the water level of the Nile.”30 Rwanda joined later while Ethiopia

Extreme Events on a Low-Gradient River and Delta: Evidence for Sediment Mass Movements on the Subaqueous Delta and a Mechanism for Creating Hyperpycnal Flow onto the Shelf

NASA Astrophysics Data System (ADS)

Dellapenna, T. M.; Carlin, J. A.; Williams, J. R.

2016-02-01

The Brazos River empties into the Gulf of Mexico (GOM) forming a wave-influenced, muddy, subaqueous delta (SAD). Recent research in the estuarine reach of the river and on the SAD, however, found evidence for significant mass wasting of the delta-front and potential evidence of hyperpycnal flow, a processes typically associated with higher gradient and higher sediment yield rivers. The study used high-resolution geophysics on the SAD and water-column profiling in the lower river to investigate the transfer to and fate of fluvial sediment on the shelf. The SAD side scan mosaic combined with core data reveal that the eastern portion was dominated by exposed relict, consolidated sediment; an erosional scarp along the upper shoreface; and a thinning of the Holocene strata immediately downslope of the scarp. Holocene strata thickness increases into deeper water. These features suggest sediment mass wasting on the delta front. After rapidly prograding during the early and mid 20th century, reductions in sediment load due anthropogenic influences, and a shift in the primary depocenter lead to erosion on these abandoned portions of the delta. During an elevated fluvial discharge event, a >1 m thick fluid mud layer was found along a 6 km span of the river 2 km upstream from the mouth. The river's salt wedge was shown to inhibit sediment export from the river to the GOM, and facilitate deposition of mud in the lower river. We believe that the mud layer in the lower river builds during moderate and low discharge periods and remobilized during increased discharge, potentially resulting in hyperpyncnal flow to the shelf. We observed suspended sediment concentrations up to 100 g/l in the fluid mud layer during this event. While our observations did not capture the transition from fluid mud to hyperpycnal flow, we believe that with persistent increased discharge the fluid mud layer could transition to hyperpycnal flow.

Heavy metals in oysters, mussels and clams collected from coastal sites along the Pearl River Delta, South China.

PubMed

Fang, Zhan-Qiang; Cheung, R Y H; Wong, M H

2003-01-01

Concentrations of 8 heavy metals: cadmium (Cd), copper (Cu), zinc (Zn), lead (Pb), nickel (Ni), chromium (Cr), antimony (Sb) and tin (Sn) were examined in 3 species of bivalves ( Perna viridis, Crassostrea rivularis and Ruditapes philippinarum) collected from 25 sites along the Pearl River Delta coastal waters in the South China Sea from July to August 1996. In general, Cd, Cu, Zn and Sn concentrations in the three bivalve species collected from the Estuarine Zone were significantly higher than those collected from the Western and Eastern Zones of the Pearl River Delta, which are related to the existence of various anthropogenic activities in the catchment of the Pearl River Delta. The Western Estuarine Zone is mainly impacted hy Cr, Ni and Cu contamination. In Victoria Harbor, heavy metal contamination is mainly due to Cu and Pb, Cd, Cu and Zn concentrations in oysters were significantly higher than those in mussels and clams. This could be explained by the fact that oysters live mainly in the Estuarine Zone of the Pearl River Delta which receives most of the polluting discharges from the catchment of the Delta. During turbid condition, heavy metals( soluble or adsorbed on suspended particulates) discharged from the Delta are filtered from the water column and subsequently accumulated into the soft body tissues of oysters. Heavy metal concentrations in the three bivalve species were compared with the maximum permissible levels of heavy metals in seafood regulated by the Public Health and Municipal Services Ordinance, Laws of Hong Kong, and it was revealed that Cd and Cr concentrations in the three bivalve species exceeded the upper limits. At certain hotspots in the Delta, the maximum acceptable daily load for Cd was also exceeded.

Coastal processes of the Elwha River delta: Chapter 5 in Coastal habitats of the Elwha River, Washington--biological and physical patterns and processes prior to dam removal

USGS Publications Warehouse

Warrick, Jonathan A.; Stevens, Andrew W.; Miller, Ian M.; Gelfenbaum, Guy; Duda, Jeffrey J.; Warrick, Jonathan A.; Magirl, Christopher S.

2011-01-01

To understand the effects of increased sediment supply from dam removal on marine habitats around the Elwha River delta, a basic understanding of the region’s coastal processes is necessary. This chapter provides a summary of the physical setting of the coast near the Elwha River delta, for the purpose of synthesizing the processes that move and disperse sediment discharged by the river. One fundamental property of this coastal setting is the difference between currents in the surfzone with those in the coastal waters offshore of the surfzone. Surfzone currents are largely dictated by the direction and size of waves, and the waves that attack the Elwha River delta predominantly come from Pacific Ocean swell from the west. This establishes surfzone currents and littoral sediment transport that are eastward along much of the delta. Offshore of the surfzone the currents are largely influenced by tidal circulation and the physical constraint to flow provided by the delta’s headland. During both ebbing and flooding tides, the flow separates from the coast at the tip of the delta’s headland, and this produces eddies on the downstream side of the headland. Immediately offshore of the Elwha River mouth, this creates a situation in which the coastal currents are directed toward the east much more frequently than toward the west. This suggests that Elwha River sediment will be more likely to move toward the east in the coastal system.

Process connectivity in a naturally prograding river delta

NASA Astrophysics Data System (ADS)

Sendrowski, Alicia; Passalacqua, Paola

2017-03-01

River deltas are lowland systems that can display high hydrological connectivity. This connectivity can be structural (morphological connections), functional (control of fluxes), and process connectivity (information flow from system drivers to sinks). In this work, we quantify hydrological process connectivity in Wax Lake Delta, coastal Louisiana, by analyzing couplings among external drivers (discharge, tides, and wind) and water levels recorded at five islands and one channel over summer 2014. We quantify process connections with information theory, a branch of mathematics concerned with the communication of information. We represent process connections as a network; variables serve as network nodes and couplings as network links describing the strength, direction, and time scale of information flow. Comparing process connections at long (105 days) and short (10 days) time scales, we show that tides exhibit daily synchronization with water level, with decreasing strength from downstream to upstream, and that tides transfer information as tides transition from spring to neap. Discharge synchronizes with water level and the time scale of its information transfer compares well to physical travel times through the system, computed with a hydrodynamic model. Information transfer and physical transport show similar spatial patterns, although information transfer time scales are larger than physical travel times. Wind events associated with water level setup lead to increased process connectivity with highly variable information transfer time scales. We discuss the information theory results in the context of the hydrologic behavior of the delta, the role of vegetation as a connector/disconnector on islands, and the applicability of process networks as tools for delta modeling results.

New insights into hydrologic sources and sinks in the Nile Basin: A multi-source satellite data analysis

NASA Astrophysics Data System (ADS)

Senay, G. B.; Velpuri, N. M.; Bohms, S.; Demissie, Y.; Gebremichael, M.

2014-12-01

The Nile River is the longest in the world with a length of 6,800 km. However, the contrast between the length of the river or the size of the basin and the comparatively small volume of basin runoff generated is a unique feature of the Nile Basin. Due to non-availability of in-situ hydrologic data, we do not clearly understand the spatial distribution of hydrologic sources and sinks and how much they control input-output dynamics? In this study, we integrated satellite-derived precipitation, and modeled evapotranspiration data (2000-2012) to describe spatial variability of hydrologic sources and sinks in the Nile Basin. We also used long-term gridded runoff and river discharge data (1869-1984) to understand the discrepancy in the observed and expected flow along the Nile River. Results indicate that over 2000-2012 period, 4 out of 11 countries (Ethiopia, Tanzania, Kenya, and Uganda) in the Nile basin showed a positive water balance while three downstream countries (South Sudan, Sudan, and Egypt) showed a negative balance. The top three countries that contribute most to the flow are Ethiopia, Tanzania and Kenya. The study revealed that ~85% of the runoff generated in the Equatorial region is lost in an inter-station basin that includes the Sudd wetlands in South Sudan; this proportion is higher than the reported loss of 50% at the Sudd wetlands alone. The loss in runoff and flow volume at different sections of the river tend to be more than what can be explained by evaporation losses, suggesting a potential recharge to deeper aquifers that are not connected to the Nile channel systems. On the other hand, we also found that the expected average annual Nile flow at Aswan is larger (97 km3) than the reported amount (84 km3). Gravity Recovery and Climate Experiment (GRACE) mass deviation in storage data analysis showed that at annual time-scales, the Nile Basin shows storage change is substantial while over longer-time periods, it is minimal (<1% of basin precipitation

Circuitous to single thread: post-dam geomorphic transformation of the Colorado River in its delta

NASA Astrophysics Data System (ADS)

Mueller, E. R.; Schmidt, J. C.

2017-12-01

The Colorado River in its delta has transformed from a maze of secondary and distributary channels to an intermittent or ephemeral stream largely disconnected from formerly active channels and floodplains. Periodic post-dam floods have demonstrated that channel migration and shifting during floods increased the extent and diversity of riparian vegetation, and suggested that restoration of fluvial processes that promote re-activation of these former channels may enhance ecosystem rehabilitation. But restoration efforts in the delta are complicated by the fact that the Colorado River has the largest reservoir size in relation to its mean annual flow of any large river in North America and most of its sediment supply is completely blocked in upstream reservoirs. As a result, small controlled floods intended to inundate formerly active channels and rejuvenate riparian vegetation must consider the new relationship between stream flow and the delta's transformed geomorphology. Post-dam channel change has been dominated by the abandonment of secondary and distributary channels, with 3 to 4 meters of bed incision in the upstream part of the delta that diminishes downstream. Initial bed incision of 2 to 3 meters occurred rapidly following completion of Hoover Dam in 1936, before further upstream water development reduced delta flows to near zero by the mid-1960s. The largest post-dam floods occurred in the 1980s, which resulted in 10s to 100s of meters of lateral migration, channel switching, and the reactivation of secondary channels and floodplains rarely inundated since dam completion. Smaller flow pulses in the 1990s and 2000s further incised the thalweg to its minimum elevation, resulting in a narrow single-thread channel inset within the multi-channel surface active during the 1980s. In 2014, an experimental pulse flow was released to the river channel with a peak discharge approximately 5% of the typical pre-dam flood peak. Topographic change was confined to the main

Human-induced hydrologic and geomorphic changes in the crisscross river network of the Pearl River Delta, South China

NASA Astrophysics Data System (ADS)

Chen, Y. D.; Chen, X. H.

2003-04-01

The West River, the North River and the East River, collectively called the Pearl River, have a total drainage area of 453,690 km2 in southern and southwestern China and flow into the South China Sea. The three rivers join together and form the Pearl River Delta (PRD) with an area of 26,820 km2. The crisscross river network (density: 0.68-1.07 km/km2) in the PRD is one of the most complicated deltaic drainage systems in the world. As the region experiencing the most rapid economic growth in China over the past two decades, the PRD has witnessed massive changes in both the social and the natural environment, leading to an urgent need of studying regional environmental changes caused by intensive human activities. This paper aims to summarize and illustrate a variety of human-induced hydrologic and geomorphic changes in the PRD river network and to present an analysis of the causes and effects of these changes. Findings of this study will help decision-makers to formulate river management and mitigation strategies and policies in the region. The hydrologic characteristics of the PRD river network have been altered to varying degrees in the following three main aspects. First and most importantly, stage has become higher or lower over the past several decades in an uneven manner in different parts of the delta. From the early 1950s to the 1980s, scattered and small embankments were enlarged and combined to expand land mass and reduce flood hazards in the PRD. However, reduction of water surface area and concentration of flow into major channels generally caused stage to go up slightly. Since the early 1990s, stage in the upper part of the PRD has significantly dropped down while the opposite situation has become more and more common in the central PRD where enormous flood damages have occurred. Secondly, corresponding to the stage changes, the stage-discharge relationship has been substantially modified, as evidenced by over 2 m drop of stage for the same amount of

Streamflow and selenium loads during synoptic sampling of the Gunnison River and its tributaries near Delta, Colorado, November 2015

USGS Publications Warehouse

Stevens, Michael R.; Leib, Kenneth J.; Thomas, Judith C.; Bauch, Nancy J.; Richards, Rodney J.

2018-06-13

In response to the need for more information about selenium (Se) sources and transport, the U.S. Geological Survey, in cooperation with the Colorado Water Conservation Board, completed a study that characterized Se loads in a reach of the Gunnison River between Delta and Grand Junction, Colo. This report identifies where possible dissolved Se loading is occurring in a study reach in the Lower Gunnison River Basin between Delta and Grand Junction on November 19, 2015.The combined Se loads from the Gunnison River at Delta (site 3) and the Uncompahgre River at Delta (site 4) were about 95 percent of the load at the furthest downstream main-stem sample location at the Gunnison River below Roubideau Creek near Delta (site 20) (31.6 and 33.4 pounds per day, respectively), indicating that about 5 percent of the total load (1.8 pounds) was potentially contributed from diffuse groundwater inflow. Main-stem streamflow accounting during November 2015 in a downstream direction was not supportive of substantial net gains or losses in the main-stem water balance.The cumulative load from measured tributary inflows downstream from the Uncompahgre River confluence only amounted to 1.2 pounds of the main-stem loads (1.8 pounds gain) from site 4 to the end of the synoptic reach at site 20. The remaining 33 percent (about 0.6 pounds) of Se load increase was not accounted for by known tributary inflow. Yet, the small changes in the streamflow mass balance in the same reach does not strongly support a net inflow explanation for the apparent gain in load.Based on the results of the loading and streamflow analysis, when errors in the loading estimates are considered, there is no conclusive evidence of an appreciable amount of Se load that is unaccounted for in the study reach of the Gunnison River as was originally hypothesized. Differences determined from comparisons of cumulative tributary loads and Gunnison River main-stem loads for this study are within error estimates of the main

Composition, biomass and structure of mangroves within the Zambezi River Delta

Treesearch

Carl C. Trettin; Christina E. Stringer; Stan Zarnoch

2015-01-01

We used a stratified random sampling design to inventory the mangrove vegetation within the Zambezi River Delta, Mozambique, to provide a basis for estimating biomass pools. We used canopy height, derived from remote sensing data, to stratify the inventory area, and then applied a spatial decision support system to objectively allocate sample plots among five...

Water quality in select regions of Cauvery Delta River basin, southern India, with emphasis on monsoonal variation.

PubMed

Solaraj, Govindaraj; Dhanakumar, Selvaraj; Murthy, Kuppuraj Rutharvel; Mohanraj, Rangaswamy

2010-07-01

Delta regions of the Cauvery River basin are one of the significant areas of rice production in India. In spite of large-scale utilization of the river basin for irrigation and drinking purposes, the lack of appropriate water management has seemingly deteriorated the water quality due to increasing anthropogenic activities. To assess the extent of deterioration, physicochemical characteristics of surface water were analyzed monthly in select regions of Cauvery Delta River basin, India, during July 2007 to December 2007. Total dissolved solids, chemical oxygen demand, and phosphate recorded maximum levels of 1,638, 96, and 0.43 mg/l, respectively, exceeding the permissible levels at certain sampling stations. Monsoonal rains in Cauvery River basin and the subsequent increase in river flow rate influences certain parameters like dissolved solids, phosphate, and dissolved oxygen. Agricultural runoff from watershed, sewage, and industrial effluents are suspected as probable factors of water pollution.

Analysis of relationships between land surface temperature and land use changes in the Yellow River Delta

NASA Astrophysics Data System (ADS)

Ning, Jicai; Gao, Zhiqiang; Meng, Ran; Xu, Fuxiang; Gao, Meng

2018-06-01

This study analyzed land use and land cover changes and their impact on land surface temperature using Landsat 5 Thematic Mapper and Landsat 8 Operational Land Imager and Thermal Infrared Sensor imagery of the Yellow River Delta. Six Landsat images comprising two time series were used to calculate the land surface temperature and correlated vegetation indices. The Yellow River Delta area has expanded substantially because of the deposited sediment carried from upstream reaches of the river. Between 1986 and 2015, approximately 35% of the land use area of the Yellow River Delta has been transformed into salterns and aquaculture ponds. Overall, land use conversion has occurred primarily from poorly utilized land into highly utilized land. To analyze the variation of land surface temperature, a mono-window algorithm was applied to retrieve the regional land surface temperature. The results showed bilinear correlation between land surface temperature and the vegetation indices (i.e., Normalized Difference Vegetation Index, Adjusted-Normalized Vegetation Index, Soil-Adjusted Vegetation Index, and Modified Soil-Adjusted Vegetation Index). Generally, values of the vegetation indices greater than the inflection point mean the land surface temperature and the vegetation indices are correlated negatively, and vice versa. Land surface temperature in coastal areas is affected considerably by local seawater temperature and weather conditions.

Comprehensive assessment of soil erosion risk for better land use planning in river basins: Case study of the Upper Blue Nile River.

PubMed

Haregeweyn, Nigussie; Tsunekawa, Atsushi; Poesen, Jean; Tsubo, Mitsuru; Meshesha, Derege Tsegaye; Fenta, Ayele Almaw; Nyssen, Jan; Adgo, Enyew

2017-01-01

In the drought-prone Upper Blue Nile River (UBNR) basin of Ethiopia, soil erosion by water results in significant consequences that also affect downstream countries. However, there have been limited comprehensive studies of this and other basins with diverse agroecologies. We analyzed the variability of gross soil loss and sediment yield rates under present and expected future conditions using a newly devised methodological framework. The results showed that the basin generates an average soil loss rate of 27.5tha -1 yr -1 and a gross soil loss of ca. 473Mtyr -1 , of which, at least 10% comes from gully erosion and 26.7% leaves Ethiopia. In a factor analysis, variation in agroecology (average factor score=1.32) and slope (1.28) were the two factors most responsible for this high spatial variability. About 39% of the basin area is experiencing severe to very severe (>30tha -1 yr -1 ) soil erosion risk, which is strongly linked to population density. Severe or very severe soil erosion affects the largest proportion of land in three subbasins of the UBNR basin: Blue Nile 4 (53.9%), Blue Nile 3 (45.1%), and Jema Shet (42.5%). If appropriate soil and water conservation practices targeted ca. 77.3% of the area with moderate to severe erosion (>15tha -1 yr -1 ), the total soil loss from the basin could be reduced by ca. 52%. Our methodological framework identified the potential risk for soil erosion in large-scale zones, and with a more sophisticated model and input data of higher spatial and temporal resolution, results could be specified locally within these risk zones. Accurate assessment of soil erosion in the UBNR basin would support sustainable use of the basin's land resources and possibly open up prospects for cooperation in the Eastern Nile region. Copyright © 2016 Office national des forêts. Published by Elsevier B.V. All rights reserved.

Temporal changes of land use in Asi river delta (Hatay, Southern Turkey).

PubMed

Korkmaz, Hüseyin; Cetin, Bayram; Kuscu, Veysel; Ege, Ismail; Bom, Ahmet; Ozsahin, Emre; Karatas, Atilla

2012-04-01

Increasing non-ecological land use necessitates more efficient using and utilization of land by man. Therefore, in recent years studies on sustainable land use have gained momentum. In this study, temporal change in land use, mainly between years 1940 and 2010, in Asi river delta on Southern Turkey was covered. To this end, in addition to literature, topographical maps and satellite images from year 1940 and after were used. Also, data were collected through field studies and interviews. Collected data were evaluated from geographical viewpoint using Geographical information system (GIS) and Remote sensing (RS) methods. Unplanned settlement in delta has reached levels high enough to threaten agricultural fields. Especially, greattendencyshown by Samandag city and the villages around it towards expanding into delta is an indicatorof this threat In additon, uncontrolled sand mining and touristic facilities on the coastline are also indicators of wrong land use. In future, direction of settlement to slopes around the delta rather than lowlands will be a much more ecological approach.

Spatio-temporal variability of dissolved organic nitrogen (DON), carbon (DOC), and nutrients in the Nile River, Egypt.

PubMed

Badr, El-Sayed A

2016-10-01

Increases in human activity have resulted in enhanced anthropogenic inputs of nitrogen (N) and carbon (C) into the Nile River. The Damietta Branch of the Nile is subject to inputs from industrial, agricultural, and domestic wastewater. This study investigated the distribution and seasonality of dissolved organic nitrogen (DON), dissolved organic carbon (DOC), and nutrients in the Nile Damietta Branch. Water samples were collected from 24 sites between May 2009 and February 2010. Dissolved organic nitrogen concentrations averaged 251 ± 115 μg/l, with a range of 90.2-671 μg/l, and contributed 40.8 ± 17.7 % to the total dissolved nitrogen (TDN) pool. Relative to autumn and winter, DON was a larger fraction of the TDN pool during spring and summer indicating the influence of bacterioplankton on the nitrogen cycle. Concentrations of DOC ranged from 2.23 to 11.3 mg/l with an average of 5.15 ± 2.36 mg/l, reflecting a high organic matter load from anthropogenic sources within the study area, and were highest during autumn. Higher values of biochemical oxygen demand (BOD), chemical oxygen demand (COD), DON, nitrate, and phosphate occurred downstream of the Damietta Branch and were probably due to anthropogenic inputs to the Nile from the Damietta district. A bacterial incubation experiment indicated that 52.1-95.0 % of DON was utilized by bacteria within 21 days. The decrease in DON concentration was accompanied by an increase in nitrate concentration of 54.8-87.3 %, presumably through DON mineralization. Based on these results, we recommend that water quality assessments consider DON and DOC, as their omission may result in an underestimation of the total organic matter load and impact.

Deposition, Alteration, and Resuspension of Colorado River Delta Sediments, Lake Powell, Utah

NASA Astrophysics Data System (ADS)

Kramer, N. M.; Parnell, R.

2002-12-01

Current drought conditions in the southwest United States have resulted in lowering water levels in Lake Powell, Utah. Delta sediments forming at the Colorado River inflow for the past 39 years are becoming exposed and reworked as lake levels continue to fall to over 22 meters below full pool level. Fine sediments act as a sink for pollutants by adsorbing contaminants to their surfaces. Reworking these sediments may pose a risk to water quality in the lake. We examine whether burial and time have sufficiently altered fine sediments in the delta and affected materials adsorbed on their surfaces. Fifteen lake cores and six sediment traps were collected from the sediment delta forming at the Colorado River inflow in Lake Powell. This research characterizes fine sediment mineralogy, the composition of exchangeable materials, and organic matter content within delta sediments to determine the type and amount of alteration of these sediments with cycles of burial and resuspension. We hypothesize that as sediments are reworked, organic carbon is degraded and organic nitrogen is released forming ammonium in these reducing conditions. Sediment trap samples will be used to test this hypothesis. Trap samples will be compared to subsamples from sediment cores to determine the amount of alteration of fine sediments. All samples are analyzed for organic carbon, organic nitrogen, ammonium, cation exchange capacity, exchangeable cation composition, and clay mineralogy. Organic carbon and nitrogen are analyzed using a Leco CN analyzer. Ammonium is analyzed using a Lachet ion chromatograph. Clay mineralogy is characterized using a Siemens D500 powder X-ray diffractometer. Cation exchange capacity and exchangeable cations are measured using standard soil chemical techniques. Clay mineral analyses indicate significant spatial and temporal differences in fine sediment entering the Lake Powell delta which complicates the use of a simple deposition/alteration/resuspension model using a

Influence of habitat heterogeneity on anuran diversity in Restinga landscapes of the Parnaíba River delta, northeastern Brazil

PubMed Central

Araújo, Kássio C.; Guzzi, Anderson; Ávila, Robson W.

2018-01-01

Abstract Anurans have close associations with environmental conditions and therefore represent an interesting vertebrate group for examining how resource availability and environmental variables influence species diversity. Associations between habitat heterogeneity and anuran species diversity were tested in the Restinga landscapes of the Parnaíba River delta in northeastern Brazil. Twenty-one anuran species were sampled in the rainy season during monthly excursions (December 2015 to June 2016) into areas of Restinga on two islands in the Parnaíba River delta. The fourth highest anuran diversity was found in this type of environment in Brazil and is the third in northeastern Brazil. Microenvironments, characterized by a combination of vernal pools with different vegetational and physical structures, better explained anuran species composition in the Parnaíba River delta. PMID:29780267

Influence of habitat heterogeneity on anuran diversity in Restinga landscapes of the Parnaíba River delta, northeastern Brazil.

PubMed

Araújo, Kássio C; Guzzi, Anderson; Ávila, Robson W

2018-01-01

Anurans have close associations with environmental conditions and therefore represent an interesting vertebrate group for examining how resource availability and environmental variables influence species diversity. Associations between habitat heterogeneity and anuran species diversity were tested in the Restinga landscapes of the Parnaíba River delta in northeastern Brazil. Twenty-one anuran species were sampled in the rainy season during monthly excursions (December 2015 to June 2016) into areas of Restinga on two islands in the Parnaíba River delta. The fourth highest anuran diversity was found in this type of environment in Brazil and is the third in northeastern Brazil. Microenvironments, characterized by a combination of vernal pools with different vegetational and physical structures, better explained anuran species composition in the Parnaíba River delta.

Simulation of transboundary pollutant transport action in the Pearl River delta.

PubMed

Chau, K W; Jiang, Y W

2003-09-01

The rapid economic development in The Pearl River delta region (PRDR) has exerted serious potential pollution threats to areas in the vicinity, which have complicated the task of environmental protection in Hong Kong and Macau. In this paper, a three-dimensional numerical pollutant transport model coupled with a synchronised numerical hydrodynamic model, is developed and employed to simulate the unsteady transport of a representative water quality variable chemical oxygen demand in The Pearl River Estuary. It is demonstrated that there exists a transboundary pollutant transport action between Guangdong Province and Hong Kong for the pollutants in the wastewater discharged from PRDR.

The burden of trachoma in the rural Nile Delta of Egypt: a survey of Menofiya governorate.

PubMed

Ezz al Arab, G; Tawfik, N; El Gendy, R; Anwar, W; Courtright, P

2001-12-01

Evidence of widespread distribution of trachoma in Egypt had not been clarified as previous surveys were limited to individual communities which may not have been representative of the general population. The Nile Delta of Egypt presents a unique environment for trachoma to persist. Economic improvements in the past decade have affected even the poorest rural environments; availability of electricity is now found in many rural communities. Availability of water in Nile Delta has always been good but poor hygienic conditions have been the primary factor in trachoma transmission. A survey of trachoma was undertaken in Menofiya governorate to determine if Egypt should be identified as trachoma endemic and targeted for trachoma control efforts. A multistage random cluster study design was used with the target population defined as adults aged 50 and over and children aged 2-6 years from throughout the governorate. Among preschool children only trachoma was graded while among adults presenting visual acuity and cause of vision loss or blindness were also recorded. Adults were interviewed regarding past trichiasis surgery; those currently with trichiasis or a history of trichiasis surgery were also interviewed regarding outcome of surgery. A total of 3272 children aged 2-6 and 3322 adults age 50+ were enumerated. Among the children 81.3% were examined and among the adults 73.0% were examined. Active trachoma (follicles (TF) and/or intense inflammation (TI)) was found among 36.5% (95% confidence interval (CI) 34.7-38.3%) of the children. TI was 1.89 (95% CI 1.22-2.94) times more common in rural children compared to urban children. The prevalence of trichiasis (TT) in adults was 6.5%; women had an age adjusted odds of trichiasis of 1.68 (95% CI 1.18-2.39) compared to men. Trichiasis was 2.11 times (95% CI 1.33-3.37) more common in rural Menofiya compared to urban Menofiya. TT accounts for blindness (presenting vision <3/60) in 8% of patients and accounts for 13.2% of

HABITAT ASSESSMENT USING A RANDOM PROBABILITY BASED SAMPLING DESIGN: ESCAMBIA RIVER DELTA, FLORIDA

EPA Science Inventory

Smith, Lisa M., Darrin D. Dantin and Steve Jordan. In press. Habitat Assessment Using a Random Probability Based Sampling Design: Escambia River Delta, Florida (Abstract). To be presented at the SWS/GERS Fall Joint Society Meeting: Communication and Collaboration: Coastal Systems...

First account on the sedimentological, geochemical and petrophysical record of the Messinian Salinity Crisis in the subsurface of onshore Nile Delta, Egypt.

NASA Astrophysics Data System (ADS)

Leila, Mahmoud; Moscariello, Andrea

2016-04-01

The giant Cenozoic Nile Delta system in the extreme northern part of Egypt occupies the southeastern part of the Eastern Mediterranean Basin and represents the most prolific gas province in Egypt with estimates more than 62 tcf of proven reserves (Niazi and Dahi, 2004). Despite the importance of the Messinian sediments in the Nile Delta hosting excellent petroleum reservoirs and seals (Dolson et al., 2001), they are still poorly studied. A multidisciplinary sedimentological, geochemical and petrophysical study is being carried out to unravel the depositional environment and tectonic setting before, during and after the important Messinian Salinity Crisis (MSC) period in the Eastern Mediterranean, and how this affected the eastern part of the onshore Nile Delta. The Lower Messinian Qawasim Formation consists of high to low-density turbiditic sandstones displaying several vertical stacked patterns of coarsening and fining upwards trends reflecting different pulses of sedimentation suggesting a sedimentation in a submarine fan developed at the base of shelf slope. The deeply incised valley infill, dating the Upper Messinian consists of the Abu Madi Formation made of lowstand braided and meandering fluvial sandstone interbedded with fine-grained floodplain sandstones and siltstones. The base of this unit is erosional and contains large mud clasts embedded in a fine-grained matrix. The Upper Miocene lowstand fluvial sandstones are capped by estuarine fine-grained cross laminated sandstones, siltstones/mudstones followed by an open marine mudstones of the Early Pliocene Kafr El-Sheikh Formation representing the end of the MSC and the subsequent transgression episode after the re-establishment of the connection between the Mediterranean and the Atlantic Ocean. Both the Qawasim and Abu Madi Formations display similar geochemical fingerprints from the clastic components. Recycled Cretaceous and Eocene sedimentary and granodioritic to intermediate igneous rocks located in

Sinking Coastlines: Land Subsidence at Aquaculture Facilities in the Yellow River Delta, China, measured with Differential Synthetic Aperture Radar (D-InSAR)

NASA Astrophysics Data System (ADS)

Higgins, S.; Overeem, I.; Tanaka, A.; Syvitski, J. P.

2013-12-01

Land subsidence in river deltas is a global problem. It heightens storm surges, salinates groundwater, intensifies river flooding, destabilizes infrastructure and accelerates shoreline retreat. Measurements of delta subsidence typically rely on point measures such as GPS devices, tide gauges or extensometers, but spatial coverage is needed to fully assess risk across river deltas. Differential Interferometric Synthetic Aperture Radar (D-InSAR) is a satellite-based technique that can provide maps of ground deformation with mm to cm-scale vertical resolution. We apply D-InSAR to the coast of the Yellow River Delta in China, which is dominated by aquaculture facilities and has experienced severe coastal erosion in the last twenty years. We extract deformation patterns from dry land adjacent to aquaculture facilities along the coast, allowing the first measurements of subsidence at a non-urban delta shoreline. Results show classic cones-of-depression surrounding aquaculture facilities, likely due to groundwater pumping. Subsidence rates are as high as 250 mm/y at the largest facility on the delta. These rates exceed local and global average sea level rise by nearly two orders of magnitude. If these rates continue, large aquaculture facilities in the area could induce more than a meter of relative sea level rise every five years. Given the global explosion in fish farming in recent years, these results also suggest that similar subsidence and associated relative sea level rise may present a significant hazard for other Asian megadeltas. False-color MODIS image of the Yellow River delta in September 2012. Water appears dark blue, highlighting the abundance of aquaculture facilities along the coast. Green land is primarily agricultural; brown is urban. Red boxes indicate locations of aquaculture facilities examined in this study. Figure from Higgins, S., Overeem, I., Tanaka, A., & Syvitski, J.P.M., (2013), Land Subsidence at Aquaculture Facilities in the Yellow River

Preliminary assessment of recent deposition related to a crevasse splay on the Mississippi River delta: Implications for coastal restoration

USGS Publications Warehouse

Ferina, N.F.; Flocks, J.G.; Kingdinger, Jack L.; Miner, M.D.; Motti, J. P.; Chadwick, Paul C.; Johnston, James B.

2005-01-01

Historically, the Mississippi River has replenished sediment across the lower deltaic plain, abating land loss. However, flood-control structures along the river now restrict this natural process and divert sediment from the modern delta offshore to the shelf break, thereby removing it from the coastal system. Localized crevasse splays, however, can deposit significant amounts of sediment in a short span of time.Satellite imagery and field investigations, including eight sediment vibracores, have identified a recent crevasse splay originating from Brant Bayou within the Delta National Wildlife Refuge on the lower Mississippi River delta. The splay deposits are estimated to be as much as 3 m thick and are located stratigraphically above shallow interdistributary-bay deposits. In addition, the deposits exhibit physical characteristics similar to those of large scale prograded deltas. The Bayou Brant crevasse splay began forming in 1978 and has built approximately 3.7 km2 of land. Coastal planners hope to utilize on this natural process of sediment dispersion to create new land within the deltaic plain.

Environmental Assessments in the Riparian Corridor of the Colorado River Delta

NASA Technical Reports Server (NTRS)

2001-01-01

We will develop remote sensing methods to conduct environmental assessments in the riparian corridor of the Colorado River delta, shared by the United States and Mexico. This important regional ecosystem is dependent upon US water flows, yet the most important wildlife habitats are in Mexico. The delta region is poorly known and difficult to monitor on the ground. We will use ground-validated, aerial and satellite methods to develop accurate vegetation and habitat maps and predictive hydrological and vegetation models of this ecosystem in response to US flood releases. The work products will advance our understanding of water resource issues in dryland climates and provide a specific application tool for a critical binational natural resource area.

Shoreline changes at the mouths of the Mekong River delta over the last 50 years: fluctuating sediment supply and shoreline cells

NASA Astrophysics Data System (ADS)

Anthony, E.; Besset, M.; Brunier, G.; Dussouillez, P.; Dolique, F.; Nguyen, V. L.; Goichot, M.

2014-12-01

River delta shorelines may be characterized by complex patterns of sediment transport and sequestering at various timescales in response to changes in sediment supply, hydrodynamic conditions, and deltaic self-organization. While being good indicators of delta stability, these changes also have important coastal management and defence implications. These aspects are examined with reference to the mouths of the Mekong River delta, the world's third largest delta, backbone of the Vietnamese economy and home to nearly 20 million people. We conducted an analysis of shoreline fluctuations over the last five decades using low-resolution Landsat (1973-2014), very high-resolution SPOT 5 (2003-2011) satellite imagery, topographic maps (1950, 1965), and field hydrodynamic and shoreline topographic measurements. The results show that the 250 km-long river-mouth sector of the delta shoreline has been characterized by overall accretion but with marked temporal and spatial variations. The temporal pattern is attributed to fluctuations in sediment supply due to both human activities and natural variations in catchment sediment loads (e.g., 2000-2003), and natural adjustments in delta-plain sediment storage and delivery to the coast. The spatial pattern is indicative of discrete sediment cells that may be a response to an overall decreasing sand supply, especially since 2003, following increasingly massive riverbed mining with concomitant losses in channel-bed sand. Field measurements show the prevalence of mesotidal bar-trough beaches characterized by sand migration to the southwest in response to energetic dry-season monsoon waves. Beaches underfed as a result of both wave-energy gradients and possible diminishing sand supply from the adjacent river mouths are eroded to feed accreting beaches. Understanding this cell pattern has important implications in terms of: (1) interpreting past patterns of shoreline translation involved in the construction of successive beach ridges that

Tides Stabilize Deltas until Humans Interfere

NASA Astrophysics Data System (ADS)

Hoitink, T.; Zheng Bing, W.; Vermeulen, B.; Huismans, Y.; Kastner, K.

2017-12-01

Despite global concerns about river delta degradation caused by extraction of natural resources, sediment retention by reservoirs and sea-level rise, human activity in the world's largest deltas intensifies. In this review, we argue that tides tend to stabilize deltas until humans interfere. Under natural circumstances, delta channels subject to tides are more stable than their fluvial-dominated counterparts. The oscillatory tidal flow counteracts the processes responsible for bank erosion, which explains why unprotected tidal channels migrate only slowly. Peak river discharges attenuate the tides, which creates storage space to accommodate the extra river discharge during extreme events and as a consequence, reduce flood risk. With stronger tides, the river discharge is being distributed more evenly over the various branches in a delta, preventing silting up of smaller channels. Human interference in deltas is massive. Storm surge barriers are constructed, new land is being reclaimed and large-scale sand excavation takes place, to collect building material. Evidence from deltas around the globe shows that in human-controlled deltas the tidal motion often plays a destabilizing role. In channels of the Rhine-Meuse Delta, some 100 scour holes are identified, which relates to the altered tidal motion after completion of a storm surge barrier. Sand mining has led to widespread river bank failures in the tidally-influenced Mekong Delta. The catastrophic flood event in the Gauges-Brahmaputra Delta by Cyclone Aila, which caused the inundation of an embanked polder area for over two years, was preceded by river bank erosion at the mouths of formal tidal channels that were blocked by the embankment. Efforts to predict the developments of degrading deltas are few. Existing delta models are capable of reproducing expanding deltas, which is essentially a matter of simulating the transport of sediment from source in a catchment to the sink in a delta. Processes of soil

Sustainability of massively anthropic deltas via dispersal of sediment to manage land building: results from two unique case studies, the Mississippi River (U.S.A.) and the Yellow River (China) deltas

NASA Astrophysics Data System (ADS)

Nittrouer, Jeffrey

2016-04-01

studies of both the Mississippi and Yellow rivers have been used to inform and validate numerical modeling efforts that seek to replicate the morphodynamics of the two diversions. The aim is to evaluate best practices for building deltaic landscape. Based on these research efforts, there are key similarities found for the delta systems: 1) coarse (sandy) sediment is the primary contributor to subaerial delta development, despite the abundance of mud for both rivers; 2) the influx of freshwater into estuarine regions of deltas has tremendous impact on vegetation development, and therefore the cohesion of the deltaic sediment deposit; and 3) it is feasible to produce efficient diversions that maximize sediment delivery and still provide for continued use of the riverine resource (for example, navigation of the channel by vessels). These findings are critical when considering future plans that seek sustainable management practices of other large, anthropic fluvial deltaic systems.

A review of environmental and human exposure to persistent organic pollutants in the Pearl River Delta, South China.

PubMed

Zhang, Kai; Wei, Yan-Li; Zeng, Eddy Y

2013-10-01

Rapid economic growth in South China (including Guangdong Province, Hong Kong, and Macau), particularly within the Pearl River Delta region, has resulted in severe pollution of the natural eco-environment in the last three decades. Large amounts of monitoring data on organic pollution in the Pearl River Delta have been accumulated, which allows us to conduct a fairly comprehensive assessment of the state of the Pearl River Delta and elucidate spatial and temporal patterns of pollution on a regional scale. Of various causes for environmental deterioration, negative impact from persistent organic pollutants (POPs) is a global concern. This review examines the current levels and distribution patterns of several POPs, namely DDT (and its metabolites DDD and DDE), hexachlorocyclohexanes, and polybrominated diphenyl ethers, in various environmental compartments of South China. The general information on environmental occurrence, regional behaviors, ecological effects, and human exposure of these POPs in this region are reviewed. Copyright © 2012 Elsevier B.V. All rights reserved.

Refining the link between the Holocene development of the Mississippi River Delta and the geologic evolution of Cat Island, MS: implications for delta-associated barrier islands

USGS Publications Warehouse

Miselis, Jennifer L.; Buster, Noreen A.; Kindinger, Jack G.

2014-01-01

The geologic evolution of barrier islands is profoundly influenced by the nature of the deposits underlying them. Many researchers have speculated on the origin and evolution of Cat Island in Mississippi, but uncertainty remains about whether or not the island is underlain completely or in part by deposits associated with the past growth of the Mississippi River delta. In part, this is due to a lack of comprehensive geological information offshore of the island that could augment previous stratigraphic interpretations based on terrestrial borings. An extensive survey of Cat Island and its surrounding waters was conducted, including shallow-water geophysics (e.g., high-resolution chirp seismic, side-scan sonar, and swath and single-beam bathymetry) and both terrestrial and marine vibracoring. High-resolution seismic data and vibracores from south and east of the island show two horizontally laminated silt units; marine radiocarbon dates indicate that they are St. Bernard delta complex (SBDC) deposits. Furthermore, seismic data reveal that the SBDC deposits taper off toward the southern shoreline of Cat Island and to the west, morphology consistent with the distal edge of a delta complex. The sedimentology and extent of each unit suggest that the lower unit may have been deposited during an earlier period of continuous river flow while the upper unit may represent reduced or sporadic river flow. OSL dates from the island platform (beneath beach ridge complexes) indicate three stages of terrestrial evolution: island emergence resulting from relative sea-level rise (~ 5400 ybp) island aggradation via littoral transport (~ 2500–4000 ybp) and island degradation due to delta-mediated changes in wave direction (present– ~ 3600 ybp). Finally, the combination of terrestrial and marine data shows that portions of Cat Island that are lower in elevation than the central part of the island are younger and are likely underlain by a thin layer of deltaic sediments. This

View of Spacelab module in payload bay with Earth background

NASA Image and Video Library

2016-08-12

STS083-709-030 (4-8 April 1997) --- Panorama over the Nile River, Sinai Peninsula and the Red Sea. Looking past the Orbiter's tail, this view extends from central Egypt eastward to Saudi Arabia on the horizon. Two major water systems, seen in this view, the Nile River and the Red Sea are used for world commerce and transportation in this region. The Nile is flanked immediately by agriculture then beyond by desert. This emphasizes the importance of the river waters to sustain a thriving local population. The Nile River delta is north under the clouds on the upper left-hand corner of the photo. Geologically, the Red Sea is a spreading center between the Arabian and the African Plates, and will continue to widen slowly over a long period of time.

Remote sensing for wetland mapping and historical change detection at the Nisqually River Delta

USGS Publications Warehouse

Ballanti, Laurel; Byrd, Kristin B.; Woo, Isa; Ellings, Christopher

2017-01-01

Coastal wetlands are important ecosystems for carbon storage and coastal resilience to climate change and sea-level rise. As such, changes in wetland habitat types can also impact ecosystem functions. Our goal was to quantify historical vegetation change within the Nisqually River watershed relevant to carbon storage, wildlife habitat, and wetland sustainability, and identify watershed-scale anthropogenic and hydrodynamic drivers of these changes. To achieve this, we produced time-series classifications of habitat, photosynthetic pathway functional types and species in the Nisqually River Delta for the years 1957, 1980, and 2015. Using an object-oriented approach, we performed a hierarchical classification on historical and current imagery to identify change within the watershed and wetland ecosystems. We found a 188.4 ha (79%) increase in emergent marsh wetland within the Nisqually River Delta between 1957 and 2015 as a result of restoration efforts that occurred in several phases through 2009. Despite these wetland gains, a total of 83.1 ha (35%) of marsh was lost between 1957 and 2015, particularly in areas near the Nisqually River mouth due to erosion and shifting river channels, resulting in a net wetland gain of 105.4 ha (44%). We found the trajectory of wetland recovery coincided with previous studies, demonstrating the role of remote sensing for historical wetland change detection as well as future coastal wetland monitoring.

Evapotranspiration in the Nile Basin: Identifying dynamics and drivers, 2002–2011

USGS Publications Warehouse

Alemu, Henok; Kaptue, Armel T.; Senay, Gabriel; Wimberly, Michael C.; Henebry, Geoffrey M.

2015-01-01

Analysis of the relationship between evapotranspiration (ET) and its natural and anthropogenic drivers is critical in water-limited basins such as the Nile. The spatiotemporal relationships of ET with rainfall and vegetation dynamics in the Nile Basin during 2002–2011 were analyzed using satellite-derived data. Non-parametric statistics were used to quantify ET-rainfall interactions and trends across land cover types and subbasins. We found that 65% of the study area (2.5 million km2) showed significant (p < 0.05) positive correlations between monthly ET and rainfall, whereas 7% showed significant negative correlations. As expected, positive ET-rainfall correlations were observed over natural vegetation, mixed croplands/natural vegetation, and croplands, with a few subbasin-specific exceptions. In particular, irrigated croplands, wetlands and some forests exhibited negative correlations. Trend tests revealed spatial clusters of statistically significant trends in ET (6% of study area was negative; 12% positive), vegetation greenness (24% negative; 12% positive) and rainfall (11% negative; 1% positive) during 2002–2011. The Nile Delta, Ethiopian highlands and central Uganda regions showed decline in ET while central parts of Sudan, South Sudan, southwestern Ethiopia and northeastern Uganda showed increases. Except for a decline in ET in central Uganda, the detected changes in ET (both positive and negative) were not associated with corresponding changes in rainfall. Detected declines in ET in the Nile delta and Ethiopian highlands were found to be attributable to anthropogenic land degradation, while the ET decline in central Uganda is likely caused by rainfall reduction.

Hydraulic survey and scour assessment of Bridge 524, Tanana River at Big Delta, Alaska

USGS Publications Warehouse

Heinrichs, Thomas A.; Langley, Dustin E.; Burrows, Robert L.; Conaway, Jeffrey S.

2007-01-01

Bathymetric and hydraulic data were collected August 26–28, 1996, on the Tanana River at Big Delta, Alaska, at the Richardson Highway bridge and Trans-Alaska Pipeline crossing. Erosion along the right (north) bank of the river between the bridge and the pipeline crossing prompted the data collection. A water-surface profile hydraulic model for the 100- and 500-year recurrence-interval floods was developed using surveyed information. The Delta River enters the Tanana immediately downstream of the highway bridge, causing backwater that extends upstream of the bridge. Four scenarios were considered to simulate the influence of the backwater on flow through the bridge. Contraction and pier scour were computed from model results. Computed values of pier scour were large, but the scour during a flood may actually be less because of mitigating factors. No bank erosion was observed at the time of the survey, a low-flow period. Erosion is likely to occur during intermediate or high flows, but the actual erosion processes are unknown at this time.

Nile damming as plausible cause of extinction and drop in abundance of deep-sea shrimp in the western Mediterranean over broad spatial scales

NASA Astrophysics Data System (ADS)

Cartes, J. E.; Maynou, F.; Fanelli, E.

2011-11-01

Greatly increased retention of flow in Nile River reservoirs was initiated in 1964, after completion of the Aswan High Dam, which induced important oceanographic changes in the Mediterranean Sea, including deep waters (below a depth of 150 m). Based on an analysis of data series starting in the 1940s/1950s, the giant red shrimp Aristaeomorpha foliacea has become locally extinct off of the Catalonian coasts (and elsewhere in the northwestern Mediterranean) at depths of 400-900 m, with a simultaneous and significant drop in the catches of red shrimp, Aristeus antennatus, in the second half of the 1960s. The extinction and sharp decline of deep-shrimp populations off Catalonian coast (at ca. 3200 km westwards from Nile Delta) followed the 1964 drop in Nile discharge with a delay of ca. 3-5 yrs (breakpoint analysis applied to data series). The breakpoints detected in the second half of 1960s both in Nile runoff and shrimps’ abundance were independent of climatic events in the study area (e.g. changes in NAO) and occurred before the increase in fishing effort off Catalonian coasts (breakpoint in 1973-1974). The Levantine Intermediate Water (LIW), inhabited by A. foliacea in the western Basin, had significant temperature (T) and salinity (S) increases in the 1950-1970 period, and Nile damming has contributed about 45% of the total S increase of Western Mediterranean deep-water masses from the 1960s to the late 1990s (Skliris and Lascaratos, 2004). This had to increase, for instance, LIW salinity at its formation site in the eastern Mediterranean. Nile damming was probably a triggering factor for the extinction/drop in abundance of deep-sea shrimp off Catalonian coasts.

Effects of the proposed California WaterFix North Delta Diversion on survival of juvenile Chinook salmon (Oncorhynchus tshawytscha) in the Sacramento-San Joaquin River Delta, northern California

USGS Publications Warehouse

Perry, Russell W.; Pope, Adam C.

2018-05-11

The California Department of Water Resources and Bureau of Reclamation propose new water intake facilities on the Sacramento River in northern California that would convey some of the water for export to areas south of the Sacramento-San Joaquin River Delta (hereinafter referred to as the Delta) through tunnels rather than through the Delta. The collection of water intakes, tunnels, pumping facilities, associated structures, and proposed operations are collectively referred to as California WaterFix. The water intake facilities, hereinafter referred to as the North Delta Diversion (NDD), are proposed to be located on the Sacramento River downstream of the city of Sacramento and upstream of the first major river junction where Sutter Slough branches from the Sacramento River. The NDD can divert a maximum discharge of 9,000 cubic feet per second (ft3 /s) from the Sacramento River, which reduces the amount of Sacramento River inflow into the Delta. In this report, we conduct four analyses to investigate the effect of the NDD and its proposed operation on survival of juvenile Chinook salmon (Oncorhynchus tshawytscha). All analyses used the results of a Bayesian survival model that allowed us to simulate travel time, migration routing, and survival of juvenile Chinook salmon migrating through the Delta in response to NDD operations, which affected both inflows to the Delta and operation of the Delta Cross Channel (DCC). For the first analysis, we evaluated the effect of the NDD bypass rules on salmon survival. The NDD bypass rules are a set of operational rule curves designed to provide adaptive levels of fish protection by defining allowable diversion rates as a function of (1) Sacramento River discharge as measured at Freeport, and (2) time of year when endangered runs requiring the most protection are present. We determined that all bypass rule curves except constant low-level pumping (maximum diversion of 900 ft3 /s) could cause a sizeable decrease in survival by as

Experimental Investigation of River Avulsion and Land-Loss on a Backwater-Influenced Delta Undergoing Sea Level Rise

NASA Astrophysics Data System (ADS)

Sikes, K.; Chadwick, A. J.; Lamb, M. P.; Fuller, B. M.

2016-12-01

Predicting the frequency of river channel avulsions and the rate of land-loss on deltas is important for hazard mitigation, ecological protection, and coastal sustainability, especially given modern rates of relative sea level rise. Previous work has investigated the effect of hydrodynamic backwater in mediating sedimentation patterns and channel avulsions on deltas, but the effect of sea-level rise on backwater-influenced deltas has yet to be explored in experiments. We will present preliminary results from a flume experiment designed to explore the role of sea-level rise on the evolution of a backwater-mediated delta. The experiment was conducted in the river-ocean facility at Caltech, where a 7m long, 14cm wide alluvial river drains into a 6m by 3m "ocean" basin under subcritical flow conditions. We used periodic flood events with different discharges to produce persistent non-uniform flow with a backwater length of 1m. Using a combination of image processing and topographic scans, we will characterize the frequency of backwater-mediated avulsions and the evolution of discrete deltaic lobes under a series of steady sea-level rise rates of different magnitude. We predict that, under moderate rise rates, enhanced aggradation will cause channels to avulse at an accelerated pace, replenishing inactive lobes more quickly and naturally acting to mitigate the extent of drowning along the delta shoreline. However, for higher rise rates, we hypothesize that rapid shoreline retreat may shift the backwater zone upstream, leading to the complete abandonment of deltaic lobes.

Modern Pearl River Delta and Permian Huainan coalfield, China: A comparative sedimentary facies study

USGS Publications Warehouse

Suping, P.; Flores, R.M.

1996-01-01

Sedimentary facies types of the Pleistocene deposits of the Modern Pearl River Delta in Guangdong Province, China and Permian Member D deposits in Huainan coalfield in Anhui Province are exemplified by depositional facies of anastomosing fluvial systems. In both study areas, sand/sandstone and mud/mudstone-dominated facies types formed in diverging and converging, coeval fluvial channels laterally juxtaposed with floodplains containing ponds, lakes, and topogenous mires. The mires accumulated thin to thick peat/coal deposits that vary in vertical and lateral distribution between the two study areas. This difference is probably due to attendant sedimentary processes that affected the floodplain environments. The ancestral floodplains of the Modern Pearl River Delta were reworked by combined fluvial and tidal and estuarine processes. In contrast, the floodplains of the Permian Member D were mainly influenced by freshwater fluvial processes. In addition, the thick, laterally extensive coal zones of the Permian Member D may have formed in topogenous mires that developed on abandoned courses of anastomosing fluvial systems. This is typified by Seam 13-1, which is a blanket-like body that thickens to as much as 8 in but also splits into thinner beds. This seam overlies deposits of diverging and converging, coeval fluvial channels of the Sandstone D, and associated overbank-floodplain deposits. The limited areal extent of lenticular Pleistocene peat deposits of the Modern Pearl River Delta is due to their primary accumulation in topogenous mires in the central floodplains that were restricted by contemporaneous anastomosing channels.

Integrated seismic tools to delineate Pliocene gas-charged geobody, offshore west Nile delta, Egypt

NASA Astrophysics Data System (ADS)

Othman, Adel A. A.; Bakr, Ali; Maher, Ali

2017-06-01

Nile delta province is rapidly emerging as a major gas province; commercial gas accumulations have been proved in shallow Pliocene channels of El-Wastani Formation. Solar gas discovery is one of the Turbidities Slope channels within the shallow Pliocene level that was proved by Solar-1 well. The main challenge of seismic reservoir characterization is to discriminate between Gas sand, Water sand and Shale, and extracting the gas-charged geobody from the seismic data. A detailed study for channel connectivity and lithological discrimination was established to delineate the gas charged geobody. Seismic data, being non-stationary in nature, have varying frequency content in time. Spectral decomposition of a seismic signal aims to characterize the time-dependent frequency response of subsurface rocks and reservoirs for imaging and mapping of bed thickness and geologic discontinuities. Spectral decomposition unravels the seismic signal into its constituent frequencies. A crossplot between P-wave Impedance (Ip) and S-wave Impedance (Is) derived from well logs (P-wave velocity, S-wave velocity and density) can be used to discriminate between gas-bearing sand, water-bearing sand, and shale. From Ip vs. Is crossplot, clear separation occurs in the P-impedance so post stack inversion is enough to be applied. Integration between Inversion results and Ip vs. Is crossplot cutoffs help to generate 3D lithofacies cubes, which is used to extract facies geobodies.

Relevance of the Paraná River hydrology on the fluvial water quality of the Delta Biosphere Reserve.

PubMed

Puig, Alba; Olguín Salinas, Héctor F; Borús, Juan A

2016-06-01

The increasing frequency of extreme events in large rivers may affect not only their flow, but also their water quality. In the present study, spatial and temporal changes in fluvial physico-chemical variables were analyzed in a mega-river delta during two extreme hydrological years (La Niña-El Niño) and related to potential explanatory factors. Basic water variables were evaluated in situ at 13 points (distant 2-35 km from each other) in watercourses of the Delta Biosphere Reserve (890 km(2)) in the Lower Paraná River (Argentina) in nine surveys (October 2008-July 2010) without meteorological tides. Samples for laboratory analyses were collected from each main river. Multivariate tests by permutations were applied. The period studied was influenced by a drought, within a long period dominated by low flows combined with dry weather and wildfires, and a large (10 years of recurrence) and prolonged (7 months) flood. The hydrological phase, followed by the season and the hydrological year (according to the ENSO event) were the principal explanatory factors of the main water quality changes, whereas the drainage sub-basin and the fluvial environment (river or stream) were secondary explanatory factors. During the drought period, conductivity, turbidity, and associated variables (e.g., major ions, silicon, and iron concentrations) were maximal, whereas real color was minimal. In the overbanking flood phase, pH and dissolved oxygen concentration were minimal, whereas real color was maximal. Dissolved oxygen saturation was also low in the receding flood phase and total major ion load doubled after the arrival of the overbanking stage. The water quality of these watercourses may be affected by the combination of several influences, such as the Paraná River flow, the pulses with sediments and solutes from the Bermejo River, the export of the Delta floodplain properties mainly by the flood, the season, and the saline tributaries to the Lower Paraná River. The high

Sources of excess urban carbonaceous aerosol in the Pearl River delta region, China

EPA Science Inventory

Carbonaceous aerosol is one of the important constituents of fine particulate matter (PM2.5) in Southern China, including the Pearl River Delta (PRD) region and Hong Kong (HK). During the study period (October and December of 2002, and March and June of 2003), the monthly average...

Martian deltas: Morphology and distribution

NASA Technical Reports Server (NTRS)

Rice, J. W., Jr.; Scott, D. H.

1993-01-01

Recent detailed mapping has revealed numerous examples of Martian deltas. The location and morphology of these deltas are described. Factors that contribute to delta morphology are river regime, coastal processes, structural stability, and climate. The largest delta systems on Mars are located near the mouths of Maja, Maumee, Vedra, Ma'adim, Kasei, and Brazos Valles. There are also several smaller-scale deltas emplaced near channel mouths situated in Ismenius Lacus, Memnonia, and Arabia. Delta morphology was used to reconstruct type, quantity, and sediment load size transported by the debouching channel systems. Methods initially developed for terrestrial systems were used to gain information on the relationships between Martian delta morphology, river regime, and coastal processes.

Variation in Ground Shaking on the Fraser River Delta (Greater Vancouver, Canada)

NASA Astrophysics Data System (ADS)

Cassidy, J. F.; Rogers, G. R.

2003-04-01

The thick, soft soils of the Fraser River delta, just south of Vancouver, Canada, are home to critical infrastructure such as one of North America's busiest port facilities, Canada's second busiest airport, and key transportation and power-transmission facilities for 2-3 million people. This area is also one of the most seismically active regions in Canada. We have utilised recent three-component, digital records of recent moderate (1996 M=5.1 at 200 km distance, 1997 M=4.3 at 40 km distance) and large (2001 M=6.8 at 300 km distance) earthquakes to examine the response to seismic shaking in the greater Vancouver, region, with an emphasis on the site response of the Fraser River delta. These suites of accelerograms have relatively low amplitudes (maximums of 0.015g for the 1996 records, 0.024g for the 1997 records, and 0.035g for the 2001 records). The 1997 data set is significant as it contains the first three-component recordings made on bedrock in greater Vancouver, and the 2001 data set is significant as it contains long-period signal (1-10 second energy). Using the method of spectral ratios, we estimate the site response for each of the strong motion instrument soil sites. Our results show frequency-dependent amplification, with factors of up to 12 times (relative to competent bedrock) near the edge of the delta. Here, the amplification is observed over a relatively narrow frequency range of 1.5-4 Hz (0.25-0.67 s period). Near the centre of the delta(where the soft soils are thickest) peak amplification of 4-10 times(relative to competent bedrock) is measured. Relative to firm soil, the peak amplification ranges from 2-5 for the thick soil delta centre sites, and 2-6 for the delta edge sites. At higher frequencies, little or no amplification, and in many cases slight attenuation is observed. The more distant earthquakes (200-300 km) present a simpler and more predictable picture of ground motion variation than that of the 1997 earthquake (40 km distant). The

Transient modeling of the ground thermal conditions using satellite data in the Lena River delta, Siberia

NASA Astrophysics Data System (ADS)

Westermann, Sebastian; Peter, Maria; Langer, Moritz; Schwamborn, Georg; Schirrmeister, Lutz; Etzelmüller, Bernd; Boike, Julia

2017-06-01

Permafrost is a sensitive element of the cryosphere, but operational monitoring of the ground thermal conditions on large spatial scales is still lacking. Here, we demonstrate a remote-sensing-based scheme that is capable of estimating the transient evolution of ground temperatures and active layer thickness by means of the ground thermal model CryoGrid 2. The scheme is applied to an area of approximately 16 000 km2 in the Lena River delta (LRD) in NE Siberia for a period of 14 years. The forcing data sets at 1 km spatial and weekly temporal resolution are synthesized from satellite products and fields of meteorological variables from the ERA-Interim reanalysis. To assign spatially distributed ground thermal properties, a stratigraphic classification based on geomorphological observations and mapping is constructed, which accounts for the large-scale patterns of sediment types, ground ice and surface properties in the Lena River delta. A comparison of the model forcing to in situ measurements on Samoylov Island in the southern part of the study area yields an acceptable agreement for the purpose of ground thermal modeling, for surface temperature, snow depth, and timing of the onset and termination of the winter snow cover. The model results are compared to observations of ground temperatures and thaw depths at nine sites in the Lena River delta, suggesting that thaw depths are in most cases reproduced to within 0.1 m or less and multi-year averages of ground temperatures within 1-2 °C. Comparison of monthly average temperatures at depths of 2-3 m in five boreholes yielded an RMSE of 1.1 °C and a bias of -0.9 °C for the model results. The highest ground temperatures are calculated for grid cells close to the main river channels in the south as well as areas with sandy sediments and low organic and ice contents in the central delta, where also the largest thaw depths occur. On the other hand, the lowest temperatures are modeled for the eastern part, which is an

Natural Selection in a Bangladeshi Population from the Cholera-Endemic Ganges River Delta

PubMed Central

Karlsson, Elinor K.; Harris, Jason B.; Tabrizi, Shervin; Rahman, Atiqur; Shlyakhter, Ilya; Patterson, Nick; O'Dushlaine, Colm; Schaffner, Stephen F.; Gupta, Sameer; Chowdhury, Fahima; Sheikh, Alaullah; Shin, Ok Sarah; Ellis, Crystal; Becker, Christine E.; Stuart, Lynda M.; Calderwood, Stephen B.; Ryan, Edward T.; Qadri, Firdausi; Sabeti, Pardis C.; LaRocque, Regina C.

2015-01-01

As an ancient disease with high fatality, cholera has likely exerted strong selective pressure on affected human populations. We performed a genome-wide study of natural selection in a population from the Ganges River Delta, the historic geographic epicenter of cholera. We identified 305 candidate selected regions using the Composite of Multiple Signals (CMS) method. The regions were enriched for potassium channel genes involved in cyclic AMP-mediated chloride secretion and for components of the innate immune system involved in NF-κB signaling. We demonstrate that a number of these strongly selected genes are associated with cholera susceptibility in two separate cohorts. We further identify repeated examples of selection and association in an NF-kB / inflammasome-dependent pathway that is activated in vitro by Vibrio cholerae. Our findings shed light on the genetic basis of cholera resistance in a population from the Ganges River Delta and present a promising approach for identifying genetic factors influencing susceptibility to infectious diseases. PMID:23825302

Distribution and Joint Fish-Tag Survival of Juvenile Chinook Salmon Migrating through the Sacramento-San Joaquin River Delta, California, 2008

USGS Publications Warehouse

Holbrook, Christopher M.; Perry, Russell W.; Adams, Noah S.

2009-01-01

Acoustic telemetry was used to obtain the movement histories of 915 juvenile fall-run Chinook salmon (Oncorhynchus tshawytscha) through the lower San Joaquin River and Sacramento-San Joaquin Delta, California, in 2008. Data were analyzed within a release-recapture framework to estimate survival, route distribution, and detection probabilities among three migration pathways through the Delta. The pathways included the primary route through the San Joaquin River and two less direct routes (Old River and Turner Cut). Strong inferences about survival were limited by premature tag failure, but estimates of fish distribution among migration routes should be unaffected by tag failure. Based on tag failure tests (N = 66 tags), we estimated that only 55-78 percent of the tags used in this study were still functioning when the last fish was detected exiting the study area 15 days after release. Due to premature tag failure, our 'survival' estimates represent the joint probability that both the tag and fish survived, not just survival of fish. Low estimates of fish-tag survival could have been caused by fish mortality or fish travel times that exceeded the life of the tag, but we were unable to differentiate between the two. Fish-tag survival through the Delta (from Durham Ferry to Chipps Island by all routes) ranged from 0.05 +or- 0.01 (SE) to 0.06 +or- 0.01 between the two weekly release groups. Among the three migration routes, fish that remained in the San Joaquin River exhibited the highest joint fish-tag survival (0.09 +or- 0.02) in both weeks, but only 22-33 percent of tagged fish used this route, depending on the week of release. Only 4-10 percent (depending on week) of tagged fish traveled through Turner Cut, but no tagged fish that used this route were detected exiting the Delta. Most fish (63-68 percent, depending on week of release) migrated through Old River, but fish-tag survival through this route (0.05 +or- 0.01) was only about one-half that of fish that

The Copper River Delta pulse study: an interdisciplinary survey of aquatic habitats.

Treesearch

M.D. Bryant

1991-01-01

In July 1987, a 2-week synoptic survey was conducted on the wetlands of the Copper River Delta by an interdisciplinary team of scientists. Disciplines included geomorphology, limnology—water chemistry and nutrients, plankton and macroinvertebrates, anadromous fish populations, and wetland plant ecology. The purpose of this report is to present a summary of the findings...

A survey of sport fish use on the Copper River Delta, Alaska.

Treesearch

Dirk W. Lang

2010-01-01

Aerial counts, in-person interviews, and mail-in questionnaires were used to survey sport fish use during the coho salmon (Oncorhynchus kisutch Walbaum) season on the Copper River Delta, Alaska from 2002 through 2006. Angler counts provided an index of use on individual streams and were used to develop a spatial database exhibiting patterns of use...

Interdisciplinary assessment of sea-level rise and climate change impacts on the lower Nile delta, Egypt.

PubMed

Sušnik, Janez; Vamvakeridou-Lyroudia, Lydia S; Baumert, Niklas; Kloos, Julia; Renaud, Fabrice G; La Jeunesse, Isabelle; Mabrouk, Badr; Savić, Dragan A; Kapelan, Zoran; Ludwig, Ralf; Fischer, Georg; Roson, Roberto; Zografos, Christos

2015-01-15

CLImate-induced changes on WAter and SECurity (CLIWASEC) was a cluster of three complementary EC-FP7 projects assessing climate-change impacts throughout the Mediterranean on: hydrological cycles (CLIMB - CLimate-Induced changes on the hydrology of Mediterranean Basins); water security (WASSERMed - Water Availability and Security in Southern EuRope and the Mediterranean) and human security connected with possible hydro-climatic conflicts (CLICO - CLImate change hydro-COnflicts and human security). The Nile delta case study was common between the projects. CLIWASEC created an integrated forum for modelling and monitoring to understand potential impacts across sectors. This paper summarises key results from an integrated assessment of potential challenges to water-related security issues, focusing on expected sea-level rise impacts by the middle of the century. We use this common focus to illustrate the added value of project clustering. CLIWASEC pursued multidisciplinary research by adopting a single research objective: sea-level rise related water security threats, resulting in a more holistic view of problems and potential solutions. In fragmenting research, policy-makers can fail to understand how multiple issues can materialize from one driver. By combining efforts, an integrated assessment of water security threats in the lower Nile is formulated, offering policy-makers a clearer picture of inter-related issues to society and environment. The main issues identified by each project (land subsidence, saline intrusion - CLIMB; water supply overexploitation, land loss - WASSERMed; employment and housing security - CLICO), are in fact related. Water overexploitation is exacerbating land subsidence and saline intrusion, impacting on employment and placing additional pressure on remaining agricultural land and the underdeveloped housing market. All these have wider implications for regional development. This richer understanding could be critical in making better

Amplified Fragment Length Polymorphism Diversity in Cephalosporium maydis from Egypt.

PubMed

Saleh, Amgad A; Zeller, Kurt A; Ismael, Abou-Serie M; Fahmy, Zeinab M; El-Assiuty, Elhamy M; Leslie, John F

2003-07-01

ABSTRACT Cephalosporium maydis, the causal agent of late wilt of maize, was first described in Egypt in the 1960s, where it can cause yield losses of up to 40% in susceptible plantings. We characterized 866 isolates of C. maydis collected from 14 governates in Egypt, 7 in the Nile River Delta and 7 in southern (Middle and Upper) Egypt, with amplified fragment length polymorphism (AFLP) markers. The four AFLP primer-pair combinations generated 68 bands, 25 of which were polymorphic, resulting in 52 clonal haplotypes that clustered the 866 isolates into four phylogenetic lineages. Three lineages were found in both the Nile River Delta and southern Egypt. Lineage IV, the most diverse group (20 haplotypes), was recovered only from governates in the Nile River Delta. In some locations, one lineage dominated (up to 98% of the isolates recovered) and, from some fields, only a single haplotype was recovered. Under field conditions in Egypt, there is no evidence that C. maydis reproduces sexually. The nonuniform geographic distribution of the pathogen lineages within the country could be due to differences in climate or in the farming system, because host material differs in susceptibility and C. maydis lineages differ in pathogenicity.

Impacts of the dam-orientated water-sediment regulation scheme on the lower reaches and delta of the Yellow River (Huanghe): A review

NASA Astrophysics Data System (ADS)

Wang, Houjie; Wu, Xiao; Bi, Naishuang; Li, Song; Yuan, Ping; Wang, Aimei; Syvitski, James P. M.; Saito, Yoshiki; Yang, Zuosheng; Liu, Sumei; Nittrouer, Jeffrey

2017-10-01

The water-sediment regulation scheme (WSRS), beginning in 2002, is an unprecedented engineering effort to manage the Yellow River with the aims to mitigate the siltation both in the lower river channel and within the Xiaolangdi Reservoir utilizing the dam-regulated flood water. Ten years after its initial implementation, multi-disciplinary indicators allow us to offer a comprehensive review of this human intervention on a river-coastal system. The WSRS generally achieved its objective, including bed erosion in the lower reaches with increasing capacity for flood discharge and the mitigation of reservoir siltation. However, the WSRS presented unexpected disturbances on the delta and coastal system. Increasing grain size of suspended sediment and decreasing suspended sediment concentration at the river mouth resulted in a regime shift of sediment transport patterns that enhanced the disequilibrium of the delta. The WSRS induced an impulse delivery of nutrients and pollutants within a short period ( 20 days), which together with the altered hydrological cycle, impacted the estuarine and coastal ecosystem. We expect that the sediment yield from the loess region in the future will decrease due to soil-conservation practices, and the lower channel erosion will also decrease as the riverbed armors with coarser sediment. These, in combination with uncertain water discharge concomitant with climate change, increasing water demands and delta subsidence, will put the delta and coastal ocean at high environmental risks. In the context of global change, this work depicts a scenario of human impacts in the river basin that were transferred along the hydrological pathway to the coastal system and remotely transformed the different components of coastal environment. The synthesis review of the WSRS indicates that an integrated management of the river-coast continuum is crucially important for the sustainability of the entire river-delta system. The lessons learned from the WSRS in

Spatial analysis of lymphatic filariasis distribution in the Nile Delta in relation to some environmental variables using geographic information system technology.

PubMed

Hassan, A N; Dister, S; Beck, L

1998-04-01

Geographic information system (GIS) was used to analyze the spatial distribution of filariasis in the Nile Delta. The study involved 201 villages belonging to Giza, Qalubiya, Monoufiya, Gharbiya, and Dakahliya governorates. Villages with similar microfilarial (mf) prevalence rates were observed to cluster within 1-2 km distance, then, clustering started to decrease significantly with distance up to 5 km (Pearson correlation coefficient = -0.98). the likelihood of negative and high prevalence villages being contiguous was very low (approximately 1.8%, n = 612 village-pairs) indicating homogeneity in disease processes within the defined spatial scales. Of the villages located within 2 km from the main Nile branches (n = 46), 95% exhibited low prevalence. In addition, the spatial pattern of mf prevalence was shown to be negatively associated with annual rainfall and relative humidity, while it was positively associated with annual daily temperature. Average mf prevalence in warmer, relatively drier areas receiving 25 mm of rain was significantly higher (3.9%) than that in less warmer but more humid areas receiving 50 mm of rain (1.6%) (P < 0.0001). Based on the results of the present study, GIS was used to generate a "filariasis risk map" that could be used by health authorities to efficiently direct surveillance and control efforts. This investigation identified some of the factors underlying filariasis spatial pattern, quantified clustering and demonstrated the potential of GIS application in vector-borne disease epidemiology.

[Decline of Gammarus lacustris Sars (Crustacea: Amphipoda) population in the delta of the Selenga River].

PubMed

Matafonov, D V; Bazova, N V

2014-01-01

We determined the amphipod population characteristics from the water bodies of the delta of the Selenga River, where Gammarus lacustris Sars, 1863 was industrially harvested until the 1990s. In 2011, the population density of G. lacustris varied from 80 to 10 200 in Lapkhai Lake and from 80 to 2320 ind./m2 in Krivaya Channel. The low population density (< 40 ind./m2) in Gryaznoe Lake, together with the absence of the species in the waters of the former Zhilishchenskoe Lake, confirms the indications of population density decline in the associated waters of the delta. Population growth of G. lacustris was limited primarily by changes in the hydromorphology of the lakes and waterways due to floods of the early 1990s and the subsequent period of extremely low flow of the Selenga River.

Morphologic and stratigraphic evolution of muddy ebb-tidal deltas along a subsiding coast: Barataria Bay, Mississippi River delta

USGS Publications Warehouse

FitzGerald, D.M.; Kulp, M.; Penland, S.; Flocks, J.; Kindinger, J.

2004-01-01

The Barataria barrier coast formed between two major distributaries of the Mississippi River delta: the Plaquemines deltaic headland to the east and the Lafourche deltaic headland to the west. Rapid relative sea-level rise (1??03 cm year-1) and other erosional processes within Barataria Bay have led to substantial increases in the area of open water (> 775 km2 since 1956) and the attendant bay tidal prism. Historically, the increase in tidal discharge at inlets has produced larger channel cross-sections and prograding ebb-tidal deltas. For example, the ebb delta at Barataria Pass has built seaward > 2??2 km since the 1880s. Shoreline erosion and an increasing bay tidal prism also facilitated the formation of new inlets. Four major lithofacies characterize the Barataria coast ebb-tidal deltas and associated sedimentary environments. These include a proximal delta facies composed of massive to laminated, fine grey-brown to pale yellow sand and a distal delta facies consisting of thinly laminated, grey to pale yellow sand and silty sand with mud layers. The higher energy proximal delta deposits contain a greater percentage of sand (75-100%) compared with the distal delta sediments (60-80%). Associated sedimentary units include a nearshore facies consisting of horizontally laminated, fine to very fine grey sand with mud layers and an offshore facies that is composed of grey to dark grey, laminated sandy silt to silty clay. All facies coarsen upwards except the offshore facies, which fines upwards. An evolutionary model is presented for the stratigraphic development of the ebb-tidal deltas in a regime of increasing tidal energy resulting from coastal land loss and tidal prism growth. Ebb-tidal delta facies prograde over nearshore sediments, which interfinger with offshore facies. The seaward decrease in tidal current velocity of the ebb discharge produces a gradational contact between proximal and distal tidal delta facies. As the tidal discharge increases and the inlet

Cryostratigraphy, sedimentology, and the late Quaternary evolution of the Zackenberg River delta, northeast Greenland

NASA Astrophysics Data System (ADS)

Gilbert, Graham L.; Cable, Stefanie; Thiel, Christine; Christiansen, Hanne H.; Elberling, Bo

2017-05-01

The Zackenberg River delta is located in northeast Greenland (74°30' N, 20°30' E) at the outlet of the Zackenberg fjord valley. The fjord-valley fill consists of a series of terraced deltaic deposits (ca. 2 km2) formed during relative sea-level (RSL) fall. We investigated the deposits using sedimentological and cryostratigraphic techniques together with optically stimulated luminescence (OSL) dating. We identify four facies associations in sections (4 to 22 m in height) exposed along the modern Zackenberg River and coast. Facies associations relate to (I) overriding glaciers, (II) retreating glaciers and quiescent glaciomarine conditions, (III) delta progradation in a fjord valley, and (IV) fluvial activity and niveo-aeolian processes. Pore, layered, and suspended cryofacies are identified in two 20 m deep ice-bonded sediment cores. The cryofacies distribution, together with low overall ground-ice content, indicates that permafrost is predominately epigenetic in these deposits. Fourteen OSL ages constrain the deposition of the cored deposits to between approximately 13 and 11 ka, immediately following deglaciation. The timing of permafrost aggradation was closely related to delta progradation and began following the subaerial exposure of the delta plain (ca. 11 ka). Our results reveal information concerning the interplay between deglaciation, RSL change, sedimentation, permafrost aggradation, and the timing of these events. These findings have implications for the timing and mode of permafrost aggradation in other fjord valleys in northeast Greenland.

Isolation and molecular identification of Naegleria fowleri from Nile river, Egypt.

PubMed

Al-Herrawy, Ahmad Z; Gad, Mahmoud A

2015-12-01

Members of the genus Naegleria are free-living amoebae distributed in various aquatic environments. Naegleria fowleri is the only species that can cause fatal primary amoebic meningoencephalitis in humans. A total of 48 Nile water samples were collected from the water stream passing though Cairo. The samples were processed for the detection of Naegleria spp. using non-nutrient agar at 45°C. The isolates of Naegleria spp. were identified based on the morphologic criteria of trophozoite, flagellated and cyst stages. Molecular characterization of the isolates was performed using PCR. The obtained results showed that Naegleria spp. were found in 45.8% of Nile water samples by means of microscopic examination. Seasonally, the highest prevalence of Naegleria spp. was recorded in summer (66.7%). Moreover, the highest prevalence of N. fowleri was recorded in summer (25%). The occurrence of heat-tolerant Naegleria spp., especially N. fowleri, in Nile water should be considered as a potential health threat.

Holocene evolution of a wave-dominated fan-delta: Godavari delta, India

NASA Astrophysics Data System (ADS)

Saito, Y.; Nageswara Rao, K.; Nagakumar, K.; Demudu, G.; Rajawat, A.; Kubo, S.; Li, Z.

2013-12-01

The Godavari delta is one of the world's largest wave-dominated deltas. The Godavari River arises in the Western Ghats near the west coast of India and drains an area of about 3.1x10^5 km^2, flowing about 1465 km southeast across the Indian peninsula to the Bay of Bengal. The Godavari delta consists of a gentle seaward slope from its apex (12 m elevation) at Rajahmundry and a coastal beach-ridge plain over a distance of about 75 km and covers ~5200 km^2 as a delta plain. The river splits into two major distributary channels, the Gautami and the Vasishta, at a barrage constructed in the mid-1800s. The coastal environment of the deltaic coast is microtidal (~1 m mean tidal range) and wave-dominated (~1.5 m mean wave height in the June-September SW monsoon season, ~0.8 m in the NE monsoon season). Models of the Holocene evolution of the Godavari delta have changed from a zonal progradation model (e.g. Nageswara Rao & Sadakata, 1993) to a truncated cuspate delta model (Nageswara Rao et al., 2005, 2012). Twelve borehole cores (340 m total length), taken in the coastal delta plain during 2010-2013, yielded more than 100 C-14 dates. Sediment facies and C-14 dates from these and previous cores and remote-sensing data support a new delta evolution model. The Holocene coastal delta plain is divided into two parts by a set of linear beach ridges 12-14 km landward from the present shoreline in the central part of the delta. The location of the main depocenter (lobe) has shifted during the Holocene from 1) the center to 2) the west, 3) east, 4) center, 5) west, and 6) east. The linear beach ridges separate the first three from the last three stages. These lobe shifts are controlled by river channel shifts near the apex. Just as the current linear shoreline of the central part of the delta and the concave-up nearshore topography are the result of coastal erosion of a cuspate delta, the linear beach ridges indicate a former eroded shoreline. An unconformity within the deltaic

"3D Depositional Model in a Complex Incised Valley Fill: An example from the late Messinian Abu Madi Formation, Nile Delta Basin, Egypt"

NASA Astrophysics Data System (ADS)

Nasr El-Deen Badawy, A. M. E. S.; Abu El-Ata, A. S. A.

2016-12-01

The study area lies in the Central Marine Delta, which is located in the Baltim offshore concession, about 25 kms from the shoreline and 40 kms North Abu Madi-El Qara fields. The current study is aiming to give a comprehensive combined and conjugated study between well data and seismic survey interpretations. The former includes well logging data, acquired results of actual drilling and biostratigraphic study, to give an integrated picture for the considered area in a true attempt to visualize the geological and geophysical data given from both wells and seismic reflection surveys, and hence introduce an updated sequence stratigraphic framework for the Messinian sequence at the offshore Nile Delta area. The 3D geological model, based on all the available well data (faunal contents, litho-facies, log signatures…...etc.) and the seismic expressions (facies and geometry), has been constructed for the study area. This model shows that, the study area was changed from shelf (considered as erosional), to delta channels and then directed to the north. It changed to delta front mouth bars on the shoreface and affected by the main Rosetta fault to collect deposits as sand bars in the southern part on the downthrown side of the fault. Most deposits on this face were highstand system tracts. This deduced from the sequence stratigraphy study. The area was then sloped to the north, as shelf slope with the deposition of slumps, which was formed during erosions and mass flows. Some mud diapers also formed upon this slope. After dropping the sea level with the activity of some syn-sedimentary faults, some channels with sediment supply started their activities to dig their ways to the north.

3D Depositional Model in a Complex Incised Valley Fill: An Example from the Late Messinian Abu Madi Formation, Nile Delta Basin, Egypt

NASA Astrophysics Data System (ADS)

Nasr El-Deen Badawy, A. M. E. S.

2015-12-01

The study area lies in the Central Marine Delta, which is located in the Baltim offshore concession, about 25 kms from the shoreline and 40 kms North Abu Madi-El Qara fields. The current study is aiming to give a comprehensive combined and conjugated study between well data and seismic survey interpretations. The former includes well logging data, acquired results of actual drilling and biostratigraphic study, to give an integrated picture for the considered area in a true attempt to visualize the geological and geophysical data given from both wells and seismic reflection surveys, and hence introduce an updated sequence stratigraphic framework for the Messinian sequence at the offshore Nile Delta area. The 3D geological model, based on all the available well data (faunal contents, litho-facies, log signatures…...etc.) and the seismic expressions (facies and geometry), has been constructed for the study area. This model shows that, the study area was changed from shelf (considered as erosional), to delta channels and then directed to the north. It changed to delta front mouth bars on the shoreface and affected by the main Rosetta fault to collect deposits as sand bars in the southern part on the downthrown side of the fault. Most deposits on this face were highstand system tracts. This deduced from the sequence stratigraphy study. The area was then sloped to the north, as shelf slope with the deposition of slumps, which was formed during erosions and mass flows. Some mud diapers also formed upon this slope. After dropping the sea level with the activity of some syn-sedimentary faults, some channels with sediment supply started their activities to dig their ways to the north.

3D Depositional Model in a Complex Incised Valley Fill: An Example from the Late Messinian Abu Madi Formation, Nile Delta Basin, Egypt

NASA Astrophysics Data System (ADS)

Nasr El-Deen Badawy, A. M. E. S.

2016-02-01

The study area lies in the Central Marine Delta, which is located in the Baltim offshore concession, about 25 kms from the shoreline and 40 kms North Abu Madi-El Qara fields. The current study is aiming to give a comprehensive combined and conjugated study between well data and seismic survey interpretations. The former includes well logging data, acquired results of actual drilling and biostratigraphic study, to give an integrated picture for the considered area in a true attempt to visualize the geological and geophysical data given from both wells and seismic reflection surveys, and hence introduce an updated sequence stratigraphic framework for the Messinian sequence at the offshore Nile Delta area. The 3D geological model, based on all the available well data (faunal contents, litho-facies, log signatures…...etc.) and the seismic expressions (facies and geometry), has been constructed for the study area. This model shows that, the study area was changed from shelf (considered as erosional), to delta channels and then directed to the north. It changed to delta front mouth bars on the shoreface and affected by the main Rosetta fault to collect deposits as sand bars in the southern part on the downthrown side of the fault. Most deposits on this face were highstand system tracts. This deduced from the sequence stratigraphy study. The area was then sloped to the north, as shelf slope with the deposition of slumps, which was formed during erosions and mass flows. Some mud diapers also formed upon this slope. After dropping the sea level with the activity of some syn-sedimentary faults, some channels with sediment supply started their activities to dig their ways to the north.

Research on vulnerability assessments of the Huanghe (Yellow River) delta

NASA Astrophysics Data System (ADS)

qiao, shuqing; shi, xuefa

2014-05-01

Coastal zone located at the juncture of the sea, river and land, and under the influence of both land and ocean (including atmosphere), especially the sea-level rise and human activities, are vulnerable to environment and ecology. At highest risk are coastal zone of South, Southeast and East Asia with dense populations, low elevations and inadequate adaptive capacity. In China, more than 40% of the population live on the 15% of the land in coastal area and more than 70% cities located around the coastal area. The Chinese coastal region, especially river delta area has been experienced erosion, seawater intrusion and decrease in biodiversity under the combined influence of sea-level rise, tectonic subsidence and flooding. Furthermore, some kinds of human activity, such as land use, building, dam construction, reclamation from the sea and waste dumping strengthen the vulnerability of environment and ecosystem in coastal region. The coastal hazards (e.g. coastal erosion, seawater intrusion, land subsidence) and vulnerability of the Huanghe (Yelllow River) delta area are studied during the past several years. A systematic coastal assessment index is built and an evaluation model is developed using the development platform of Visual studio.Net 2005. The assessment index system includes two parts, inherent (sea level rise rate, elevation, morphology, water and sediment discharge, mean tidal range, mean wave height etc) and specific vulnerability index (population density, GDP, land utilization, protection structures etc). The assessment index are determined the weight using Analytic hierarchy process (AHP) method. Based on the research results, we better understand the current status and future change of coastal vulnerability and hazards, discuss the impact of the natural possess and human activities. Furthermore, we provide defending strategies for coastal zone vulnerability and typical coastal hazards.

Suitability of river delta sediment as proppant, Missouri and Niobrara Rivers, Nebraska and South Dakota, 2015

USGS Publications Warehouse

Zelt, Ronald B.; Hobza, Christopher M.; Burton, Bethany L.; Schaepe, Nathaniel J.; Piatak, Nadine

2017-11-16

Sediment management is a challenge faced by reservoir managers who have several potential options, including dredging, for mitigation of storage capacity lost to sedimentation. As sediment is removed from reservoir storage, potential use of the sediment for socioeconomic or ecological benefit could potentially defray some costs of its removal. Rivers that transport a sandy sediment load will deposit the sand load along a reservoir-headwaters reach where the current of the river slackens progressively as its bed approaches and then descends below the reservoir water level. Given a rare combination of factors, a reservoir deposit of alluvial sand has potential to be suitable for use as proppant for hydraulic fracturing in unconventional oil and gas development. In 2015, the U.S. Geological Survey began a program of researching potential sources of proppant sand from reservoirs, with an initial focus on the Missouri River subbasins that receive sand loads from the Nebraska Sand Hills. This report documents the methods and results of assessments of the suitability of river delta sediment as proppant for a pilot study area in the delta headwaters of Lewis and Clark Lake, Nebraska and South Dakota. Results from surface-geophysical surveys of electrical resistivity guided borings to collect 3.7-meter long cores at 25 sites on delta sandbars using the direct-push method to recover duplicate, 3.8-centimeter-diameter cores in April 2015. In addition, the U.S. Geological Survey collected samples of upstream sand sources in the lower Niobrara River valley.At the laboratory, samples were dried, weighed, washed, dried, and weighed again. Exploratory analysis of natural sand for determining its suitability as a proppant involved application of a modified subset of the standard protocols known as American Petroleum Institute (API) Recommended Practice (RP) 19C. The RP19C methods were not intended for exploration-stage evaluation of raw materials. Results for the washed samples are

Regional variations of organophosphorus flame retardants - Fingerprint of large river basin estuaries/deltas in Europe compared with China.

PubMed

Wolschke, Hendrik; Sühring, Roxana; Massei, Riccardo; Tang, Jianhui; Ebinghaus, Ralf

2018-05-01

This study reports the occurrence and distribution of organophosphorus flame retardants and plasticizer (OPEs) in sediments of eight large river basin estuaries and deltas across Europe. A robust and sensitive OPE analysis method was developed through the application of an in-cell clean-up in an accelerated solvent extraction and the use of an GC-MSMS System for instrumental analyses. OPEs were detected in all sediment samples with sum concentrations of up to 181 ng g -1 dw. A fingerprinting method was used to identify river specific pattern to compare river systems. The estuaries and deltas were chosen to have a conglomerate print of the whole river. The results are showing very similar OPE patterns across Europe with minor differences driven by local industrial input. The European estuary concentrations and patterns were compared with OPEs detected in the Xiaoquing River in China, as an example for a region with other production, usage and legislative regulations. The Chinese fingerprint differed significant from the overall European pattern. Copyright © 2018 Elsevier Ltd. All rights reserved.

Nesting ecology of Spectacled Eiders Somateria fischeri on the Indigirka River Delta, Russia

USGS Publications Warehouse

Pearce, John M.; Esler, Daniel N.; Degtyarev, Andrei G.

1998-01-01

In 1994 and 1995 we investigated breeding biology and nest site habitat of Spectacled Eiders on two study areas within the coastal fringe of the Indigirka River Delta, Russia (71°20' N, 150°20' E). Spectacled Eiders were first observed on 6 June in both years and nesting commenced by mid-June. Average clutch size declined with later nest initiation dates by 0.10 eggs per day; clutches were larger in 1994 than 1995 and were slightly larger on a coastal island study area compared to an interior area. Nesting success varied substantially between years, with estimates of 1.6% in 1994 and 27.6% in 1995. Total egg loss, through avian or mammalian predation, occurred more frequently than partial egg loss. Partial egg loss was detected in 16 nests and appeared unrelated to nest initiation date or clutch size. We found no difference among survival rates of nests visited weekly, biweekly, and those at which the hen was never flushed, suggesting that researcher presence did not adversely affect nesting success. A comparison of nine habitat variables within each study area revealed little difference between nest sites and a comparable number of randomly located sites, leading us to conclude that Spectacled Eiders nest randomly with respect to most small scale habitat features. We propose that large scale landscape features are more important indicators of nesting habitat as they may afford greater protection from land-based predators, such as the Arctic Fox. Demographic data collected during this study, along with recent conservation measures implemented by the Republic of Sakha (Yakutia), lead us to conclude that there are few threats to the Indigirka River Delta Spectacled Eider population. Presently, the Indigirka River Delta contains the largest concentration of nesting Spectacled Eiders and deserves continued monitoring and conservation.

Influence of changes in hydrodynamic conditions on cadmium transport in tidal river network of the Pearl River Delta, China.

PubMed

Dou, Ming; Zuo, Qiting; Zhang, Jinping; Li, Congying; Li, Guiqiu

2013-09-01

With rapid economic development, the Pearl River Delta (PRD) of China has experienced a series of serious heavy metal pollution events. Considering complex hydrodynamic and pollutants transport process, one-dimensional hydrodynamic model and heavy metal transport model were developed for tidal river network of the PRD. Then, several pollution emergency scenarios were designed by combining with the upper inflow, water quality and the lower tide level boundary conditions. Using this set of models, the temporal and spatial change process of cadmium (Cd) concentration was simulated. The influence of change in hydrodynamic conditions on Cd transport in tidal river network was assessed, and its transport laws were summarized. The result showed the following: Flow changes in the tidal river network were influenced remarkably by tidal backwater action, which further influenced the transport process of heavy metals; Cd concentrations in most sections while encountering high tide were far greater than those while encountering middle or low tides; and increased inflows from upper reaches could intensify water pollution in the West River (while encountering high tide) or the North River (while encountering middle or low tides).

Coastal environmental monitoring using remotely sensed data and GIS techniques in the Modern Yellow River delta, China.

PubMed

Zhang, Yang

2011-08-01

On the basis of remote sensing and GIS techniques, the Landsat data obtained in 1987, 1996, and 2008 were used to examine coastline changes in the Modern Yellow River (MYR) delta in China. The coastal land lost and gained illustrations were derived, the rates of coastal change were estimated, and the coastal parts that experienced severe changes were identified. The results revealed that the accretion rates in the MYR delta coast has been decelerating while the accretion effect remained. Taken the artificial coast from the south of ShenXianGou (SXG) to Gudong Oil Field (GOF) as the landmark, the coast in the south of the landmark showed an accretion pattern, while the coast in the west of the landmark showed an erosion pattern. Wherein, the coast from Chao River Estuary (CRE) to Zhuang 106 (Z106) showed an erosion pattern with the transition from erosion to accretion and the accelerated rates from east to west. The coast from Z106 to the south border of GOF also showed erosion pattern but significant differences existed among the internal coastal parts. The coast from the south border of GOF to XiaoDao River Estuary (XDRE) showed a pattern from rapid accretion to dynamic balance of accretion/erosion, and the trend towards erosion. The coast from XDRE to XiaoQing River Estuary (XQRE) showed slow accretion pattern. Human activities have heavily influenced the natural evolution of the MYR delta coast.

Spatial and temporal variation of biological control agents associated with Eichhornia crassipes in the Sacramento-San Joaquin River Delta, California

USDA-ARS?s Scientific Manuscript database

Invasive aquatic weeds, such as water hyacinth (Eichhornia crassipes), severely limit the ecosystem services provided by the Sacramento-San Joaquin River Delta. As part of the biological control program in the Delta, two weevils, Neochetina bruchi and N. eichhorniae (Coleoptera: Curculionidae) and a...

Changes to subaqueous delta bathymetry following a high river flow event, Wax Lake Delta, LA, USA

NASA Astrophysics Data System (ADS)

Whaling, A. R.; Shaw, J.

2017-12-01

Sediment transport capacity is increased during high river flow (flood) events which are characterized by discharges that exceed the 15 year median daily statistic. The Wax Lake Delta (WLD) in coastal Louisiana has experienced 19 of these high flow events in the past 20 years, yet the depositional patterns of single floods are rarely measured in a field-scale deltaic setting. We characterize flood deposition and erosion patterns on the subaqueous portion of the WLD by differencing two Digital Elevation Models (DEMs) constructed from bathymetric surveys before and after the third largest flood in the WLD's recorded history. The total suspended sediment discharge for the 496 day inter-survey period was 2.14x107 cubic meters measured 21 km upstream of the delta apex. The difference map showed 1.06x107 cubic meters of sediment was deposited and 8.2x106 cubic meters was eroded, yielding 2.40x106 cubic meters of net deposition in the survey area ( 79.7 km2 ). Therefore the average deposition rate was 0.061 mm/day. Channel planform remained relatively unchanged for five out of six distributary passes however Gadwall Pass experienced a maximum channel displacement of 166 m ( 1 channel width) measured from the thalweg centerline. Channel tip extension was negligible. In addition, channel displacement was not concentrated at any portion along the channel centerline. Maximum erosion occurred within channel margins and increased upstream whereas maximum deposition occurred immediately outside the channel margins. Sediment eroded from the survey area was either subsequently re-deposited or transported out of the system. Our results show that up to 77.4% of deposition in the survey area originated from sediment eroded during the flood. Surprisingly, only 11.2% of the total suspended sediment discharge was retained in the subaqueous portion of the delta after the flood. We conclude that a high flow event does not produce channel progradation. Rather, high flow causes delta

Channel Evolution Following Avulsion: an Example from the Yellow River Delta

NASA Astrophysics Data System (ADS)

Zheng, S.

2017-12-01

Long-term field observation of morphological adjustments of rivers following avulsions is lacked when studying the evolution of avulsive channel on deltas. Avulsion at the Yellow River Delta (YRD) is frequent with average lifespan of channels of only about a decade. The Qing-shui-gou channel, the recent lobe on the YRD, provides a rare opportunity for investigating channel evolution following artificial avulsion. The reasons for its longer lifespan also needs investigation of the channel evolution. In this study, we comprehensively analyzed the geomorphic adjustment of the channel based on filed survey data during 1976-2014. The evolution of the channel was impacted by anthropogenic activities, including artificial avulsion at the downstream channel reaches in 1996, alteration of runoff and sediment load through Water and Sediment Regulation Scheme (WSRS), construction of levees and dikes. Analysis on channel geometry showed that avulsions in 1976 and in 1996 both caused short-term (1 2 years) erosion at the upstream channel reaches. Following the avulsion in 1976, massive aggradation occurred at the channel reaches at the downstream of the avulsion point. A single-thread channel gradually formed, widened and enlarged as channel bed under-cut on the deposition material. As delta extended seaward and the longitudinal slope decreased with time, aggradation occurred and an alluvial ridge formed. The ratio of lateral slope to the longitudinal slope (i.e. gradient advantage) and the relative super-elevation of the channel were calculated to estimate the possibility of avulsion at the channel in the late 1990. Results showed that the slope ratio was greater than 20 locally and super-elevation near its critical value for avulsion. The fact, that natural avulsion did not occurred despite of high values of gradient advantage and super elevation, may indicate that they are not sufficient conditions for avulsion at highly human-controlled rivers, where channel boundaries are

Improved Management of the Nile River Basin Through Modeling the Sudd, a Wetland with Vital Socioeconomic and Environmental Services

NASA Astrophysics Data System (ADS)

Di Vittorio, C.; Georgakakos, A. P.

2017-12-01

The Sudd is a vast, remote wetland in South Sudan and a vital component of the Nile River Basin. While decision support tools like the Nile Decision Support Tool (Nile DST) estimate the amount of water flowing through the Sudd, they do not account for other wetland processes that sustain the ecosystem diversity and the pastoral way of life for nearly two million people who live in the area (Howell et al. 1988). An accurate hydrologic model of the Sudd would enable policy makers to appreciate and manage it in a way that benefits local inhabitants as well as the 500 million people living within the Nile region (NBI, 2016). Currently, the most widely accepted model of the Sudd was developed by Sutcliffe and Parks (1999) and is a lumped mass balance model that accounts for key water fluxes. Estimates of the aerial extent of flooding obtained from satellite and airborne imagery on a few dates were used to calibrate the model parameters over the 1905-1983 period. During the AGU Fall 2016 meeting, we presented a method for deriving the dynamic flooding extents of the Sudd on a monthly temporal resolution from 2000-2015 using MODIS (Moderate Resolution Imaging Spectrometer) land surface reflectance data (Di Vittorio & Georgakakos, 2017 in press). In the study presented here, we have used this new information to evaluate the Sutcliffe and Park's model, highlight its shortcomings, and suggest alternative modeling approaches that are accurate enough to incorporate into water management models. The alternative modelling approaches include statistical and physically based models, and the incorporation of satellite-based hydrometeorlogical data sets. This improved hydrologic model will allow stakeholders in this sensitive world region to better understand how current and future climate and water management scenarios will impact the Sudd ecosystem and local economy. References: Di Vittorio, C. A., Georgakakos, A.P. (2017). Land cover classification and wetland inundation mapping

Assessment of Environmental Flows for the Rivers of Western Ganges Delta with Special Reference to Indian Sundarban

NASA Astrophysics Data System (ADS)

Bhadra, T.; Hazra, S.; Ghosh, S.; Barman, B. C.

2016-12-01

The Indian Sundarban, situated on the western tide-dominated part of the Ganges delta was formed by the sedimentation of the Ganges and its tributaries. Freshwater is a scarce resource in the Sundarban though it is traversed by rivers. Most of the rivers of Western Ganges Delta, which used to nourish the Sundarban, have become defunct with the passage of time. To ensure sustainable flow and to enhance the flow-dependent ecosystem services in this region, assessment of environmental flows within the system is required. A pilot assessment of environment flows, supported by IUCN has been carried out in some specific river reaches of Western Ganges Delta under the present study. The holistic Building Block Methodology (BBM) has been modified and used for the assessment of environmental flows. In the modified BBM, three distinctive blocks namely Hydro-Morphology, Ecology and Socio-Economy have been selected and indicators like Ganges Dolphin (Platanista gangetica), Sundari tree (Heritiera fomes) and Hilsa fish (Tenualosa ilisha) etc. have been determined to assess the environmental flows. As the discharge data of the selected rivers are restricted in the public domain, the SWAT model has been run to generate the discharge data of the classified rivers. The Hydraulic model, HEC-RAS has been calibrated in the selected River reaches to assess the habitat availability and its changes for indicator species under different flow condition. The study reveals that River Bhagirathi-Hugli requires 150-427 cumec additional water in monsoon and 850-1127 cumec additional water in post-monsoon months for Hilsa migration, whereas 327-486 cumec additional water in pre-monsoon and dry season and 227-386 cumec additional water in post-monsoon months are required for Dolphin movement. Flow requirement of river Ichhamati has also been estimated under the present study. The total required flow for the Sundarban ecosystem to reduce the salinity level from 30ppt to 14ppt during the dry and pre

Appendix A The influence of junction hydrodynamics on entrainment of juvenile salmon into the interior Sacramento-San Joaquin River Delta

NASA Astrophysics Data System (ADS)

Ramón Casañas, Cintia; Burau, Jon; Blake, Aaron; Acosta, Mario; Rueda, Francisco

2017-04-01

River junctions where water may follow two or more alternative pathways (diffluences) could be critical points in river networks where aquatic migratory species select different migration routes. Federally listed Sacramento River Chinook salmon juveniles must survive passage through the tidal Sacramento - San Joaquin River Delta in order to successfully out-migrate to the ocean. Two of the four main migration routes identified for salmon in the Sacramento River direct them to the interior of the delta, where salmon survival is known to decrease dramatically. Migration route selection is thought to be advection-dominated, but the combination of physical and biological processes that control route selection is still poorly understood. The reach in the Sacramento-River where the entrances of the two lower-survival migration routes are located is strongly influenced by the tides, with flows reversing twice daily, and the two diffluences are located in the outside of the same Sacramento River bend where secondary circulation occurs. Three dimensional simulations are conducted, both in the Eularian and Lagrangian frame, to understand tidal and secondary-circulation effects on the migration route selection of juveniles within this reach of the Sacramento River. Although salmon behavior is reduced to the simplest (passively-driven neutrally-buoyant particles), the preliminary results here presented are consistent with previous studies that show that during the flood tide almost all the flow, and thus, all the salmon, are directed to the interior delta through these two migration routes. Simulated fish entrainment rates into the interior of the delta tend to be larger than those expected from flow entrainment calculations alone, particularly during ebb tides. Several factors account for these tendencies. First, the fraction of the flow diverted to the side channel in the shallowest layers tend to be higher than in the deeper layers, as a result of the secondary circulation

Channel-Island Connectivity Affects Water Exposure Time Distributions in a Coastal River Delta

NASA Astrophysics Data System (ADS)

Hiatt, Matthew; Castañeda-Moya, Edward; Twilley, Robert; Hodges, Ben R.; Passalacqua, Paola

2018-03-01

The exposure time is a water transport time scale defined as the cumulative amount of time a water parcel spends in the domain of interest regardless of the number of excursions from the domain. Transport time scales are often used to characterize the nutrient removal potential of aquatic systems, but exposure time distribution estimates are scarce for deltaic systems. Here we analyze the controls on exposure time distributions using a hydrodynamic model in two domains: the Wax Lake delta in Louisiana, USA, and an idealized channel-island complex. In particular, we study the effects of river discharge, vegetation, network geometry, and tides and use a simple model for the fractional removal of nitrate. In both domains, we find that channel-island hydrological connectivity significantly affects exposure time distributions and nitrate removal. The relative contributions of the island and channel portions of the delta to the overall exposure time distribution are controlled by island vegetation roughness and network geometry. Tides have a limited effect on the system's exposure time distribution but can introduce significant spatial variability in local exposure times. The median exposure time for the WLD model is 10 h under the conditions tested and water transport within the islands contributes to 37-50% of the network-scale exposure time distribution and 52-73% of the modeled nitrate removal, indicating that islands may account for the majority of nitrate removal in river deltas.

Mapping the change of Phragmites australis live biomass in the lower Mississippi River Delta marshes

USGS Publications Warehouse

Ramsey, Elijah W.; Rangoonwala, Amina

2017-07-28

Multiyear remote sensing mapping of the normalized difference vegetation index (NDVI) was carried out as an indicator of live biomass composition of the Phragmites australis (hereafter Phragmites) marsh in the lower Mississippi River Delta (hereafter delta) from 2014 to 2017. Maps of NDVI change showed that the Phragmites condition was fairly stable between May 2014 and July 2015. From July 2015 to April 2016 NDVI change indicated Phragmites suffered a widespread decline in the live biomass proportion.  Between April and September 2016, most marsh remained unchanged from the earlier period or showed improvement; although there were pockets of continued decline scattered throughout the lower delta. From September 2016 to May 2017 a pronounced and widely exhibited decline in the condition of Phragmites marsh again occurred throughout the lower delta. This final NDVI change mapping supported field observations of Phragmites decline during the same period.

Detection of West Nile virus in wild birds in Tana River and Garissa Counties, Kenya.

PubMed

Nyamwaya, Doris; Wang'ondu, Virginia; Amimo, Joshua; Michuki, George; Ogugo, Moses; Ontiri, Enoch; Sang, Rosemary; Lindahl, Johanna; Grace, Delia; Bett, Bernard

2016-11-23

West Nile fever virus is a zoonotic arboviral infection maintained in a sylvatic cycle involving mosquito vectors and birds. It is one the arboviruses whose geographical range is expanding because of climate and land use changes that enhance the densities of mosquitoes and promote mosquito-bird-human interactions. We carried out a survey to determine the reservoirs of WNV among wild birds in Tana River and Garissa counties, Kenya. Blood samples were obtained from 361 randomly trapped wild birds. Using real-time polymerase chain reaction (PCR), all samples were screened for WNV using gene specific primer sets amplifying a portion of the E region of the genome encoding the envelope protein. Sixty five (65) out of 361 birds screened tested positive for WNV on real-time PCR assay. Sequencing of the selected positive samples reveals that the isolated WNV were most closely related to strains isolated from China (2011). A regression analysis indicated that sampling location influenced the occurrence of WNV while species, age, weight and sex of the birds did not have any effect. This study provides baseline information on the existing circulation of WNV in this region among wild bird reservoirs that could spill over to the human population and points to the need for implementation of surveillance programs to map the distribution of the virus among reservoirs. Awareness creation about West Nile fever in this region is important to improve its detection and management.

Geochemical constraints on the provenance and depositional environment of the Messinian sediments, onshore Nile Delta, Egypt: Implications for the late Miocene paleogeography of the Mediterranean

NASA Astrophysics Data System (ADS)

Leila, Mahmoud; Moscariello, Andrea; Šegvić, Branimir

2018-07-01

The Messinian sequence rocks in the Nile Delta present prolific hydrocarbon reservoirs and are, therefore, of great importance from the aspect of petroleum exploration and development strategies. Yet, little is known about their tectonic provenance and depositional setting. This study focuses on the geochemical signatures archived in the Messinian siliciclastic sediments to employ them as a powerful tool to elucidate the basin evolution during the Messinian salinity crisis (MSC). The pre-MSC Qawasim sediments are texturally and compositionally immature. They are enriched in lithic fragments, foraminiferal bioclasts, and rounded heavy minerals suggesting a significant contribution from the pre-existing Cretaceous-Eocene mixed carbonate-siliciclastic rocks bordering the Nile Delta. In contrast, the textural and mineralogical compositions as well as a range of geochemical proxies (e.g., chemical index of alteration and weathering CIA, CIW as well as index of chemical variability ICV and Zr/Sc ratio) are in favor of prolonged weathering and at least second-cycle origin of the MSC Abu Madi sediments. The mutually correspondent elemental ratios (e.g., Al2O3/TiO2, K2O/Na2O, Zr/Hf, Rb/Sr, Cr/Zr, and Cr/Th) and uniform weathering trends are indicatives for a similar provenance of the pre-MSC Qawasim and MSC Abu Madi sediments. Rare earth element (REE) distribution reveals a significant enrichment in LREE, depletion in HREE, relatively high (La/Yb)N (mean > 9), low (Gd/Yb)N (mean < 2) and a pronounced negative Eu anomaly (mean∼0.75) in the studied Messinian facies, characteristics of upper continental sources of mainly felsic to intermediate rock affiliations. Provenance proxy ratios (e.g., Al/Ti, La/Sc, Th/Sc, La/Co and Eu/Eu*) along with the low concentration of transition trace elements (Cr, Ni, Co, Ni) are effectively ruling out the contribution from mafic and ultramafic rocks. The investigated Messinian sedimentary facies have similar passive margin geotectonic

Understanding the hydrologic sources and sinks in the Nile Basin using multisource climate and remote sensing data sets

USGS Publications Warehouse

Senay, Gabriel; Velpuri, Naga Manohar; Bohms, Stefanie; Demissie, Yonas; Gebremichael, Mekonnen

2014-01-01

In this study, we integrated satellite-drived precipitation and modeled evapotranspiration data (2000–2012) to describe spatial variability of hydrologic sources and sinks in the Nile Basin. Over 2000–2012 period, 4 out of 11 countries (Ethiopia, Tanzania, Kenya, and Uganda) in the Nile Basin showed a positive water balance while three downstream countries (South Sudan, Sudan, and Egypt) showed a negative balance. Gravity Recovery and Climate Experiment (GRACE) mass deviation in storage data analysis showed that at annual timescales, the Nile Basin storage change is substantial while over longer time periods, it is minimal (<1% of basin precipitation). We also used long-term gridded runoff and river discharge data (1869–1984) to understand the discrepancy in the observed and expected flow along the Nile River. The top three countries that contribute most to the flow are Ethiopia, Tanzania, and Kenya. The study revealed that ∼85% of the runoff generated in the equatorial region is lost in an interstation basin that includes the Sudd wetlands in South Sudan; this proportion is higher than the literature reported loss of 50% at the Sudd wetlands alone. The loss in runoff and flow volume at different sections of the river tend to be more than what can be explained by evaporation losses, suggesting a potential recharge to deeper aquifers that are not connected to the Nile channel systems. On the other hand, we also found that the expected average annual Nile flow at Aswan is greater (97 km3) than the reported amount (84 km3). Due to the large variations of the reported Nile flow at different locations and time periods, the study results indicate the need for increased hydrometeorological instrumentation of the basin. The study also helped improve our understanding of the spatial dynamics of water sources and sinks in the Nile Basin and identified emerging hydrologic questions that require further attention.

Understanding the hydrologic sources and sinks in the Nile Basin using multisource climate and remote sensing data sets

NASA Astrophysics Data System (ADS)

Senay, Gabriel B.; Velpuri, Naga Manohar; Bohms, Stefanie; Demissie, Yonas; Gebremichael, Mekonnen

2014-11-01

In this study, we integrated satellite-drived precipitation and modeled evapotranspiration data (2000-2012) to describe spatial variability of hydrologic sources and sinks in the Nile Basin. Over 2000-2012 period, 4 out of 11 countries (Ethiopia, Tanzania, Kenya, and Uganda) in the Nile Basin showed a positive water balance while three downstream countries (South Sudan, Sudan, and Egypt) showed a negative balance. Gravity Recovery and Climate Experiment (GRACE) mass deviation in storage data analysis showed that at annual timescales, the Nile Basin storage change is substantial while over longer time periods, it is minimal (<1% of basin precipitation). We also used long-term gridded runoff and river discharge data (1869-1984) to understand the discrepancy in the observed and expected flow along the Nile River. The top three countries that contribute most to the flow are Ethiopia, Tanzania, and Kenya. The study revealed that ˜85% of the runoff generated in the equatorial region is lost in an interstation basin that includes the Sudd wetlands in South Sudan; this proportion is higher than the literature reported loss of 50% at the Sudd wetlands alone. The loss in runoff and flow volume at different sections of the river tend to be more than what can be explained by evaporation losses, suggesting a potential recharge to deeper aquifers that are not connected to the Nile channel systems. On the other hand, we also found that the expected average annual Nile flow at Aswan is greater (97 km3) than the reported amount (84 km3). Due to the large variations of the reported Nile flow at different locations and time periods, the study results indicate the need for increased hydrometeorological instrumentation of the basin. The study also helped improve our understanding of the spatial dynamics of water sources and sinks in the Nile Basin and identified emerging hydrologic questions that require further attention.

Socioeconomic dynamics of water quality in the Egyptian Nile

NASA Astrophysics Data System (ADS)

Malik, Maheen; Nisar, Zainab; Karakatsanis, Georgios

2016-04-01

The Nile River remains the most important source of freshwater for Egypt as it accounts for nearly all of the country's drinking and irrigation water. About 95% of the total population is accounted to live along the Banks of the Nile(1). Therefore, water quality deterioration in addition to general natural scarcity of water in the region(2) is the main driver for carrying out this study. What further aggravates this issue is the water conflict in the Blue Nile region. The study evaluates different water quality parameters and their concentrations in the Egyptian Nile; further assessing the temporal dynamics of water quality in the area with (a) the Environmental Kuznets Curve (EKC)(3) and (b) the Jevons Paradox (JP)(4) in order to identify water quality improvements or degradations using selected socioeconomic variables(5). For this purpose various environmental indicators including BOD, COD, DO, Phosphorus and TDS were plotted against different economic variables including Population, Gross Domestic Product (GDP), Annual Fresh Water Withdrawal and Improved Water Source. Mathematically, this was expressed by 2nd and 3rd degree polynomial regressions generating the EKC and JP respectively. The basic goal of the regression analysis is to model and highlight the dynamic trend of water quality indicators in relation to their established permissible limits, which will allow the identification of optimal future water quality policies. The results clearly indicate that the dependency of water quality indicators on socioeconomic variables differs for every indicator; while COD was above the permissible limits in all the cases despite of its decreasing trend in each case, BOD and phosphate signified increasing concentrations for the future, if they continue to follow the present trend. This could be an indication of rebound effect explained by the Jevons Paradox i.e. water quality deterioration after its improvement, either due to increase of population or intensification

Pesticides in soil and sediment of a dyke-protected area of the Red River Delta, Vietnam

NASA Astrophysics Data System (ADS)

Braun, Gianna; Bläsing, Melanie; Kruse, Jens; Amelung, Wulf; Renaud, Fabrice; Sebesvari, Zita

2017-04-01

Coastal regions are densely populated but at the same time represent important agricultural areas for food production of the growing world population. To sustain high agricultural yields, in monocultures such as permanent rice systems, pesticides are used in high quantity and frequency. While earlier studies monitored the fate of pesticides in paddy rice systems, the overall fate of these compounds is altered nowadays due to the construction of dykes, which are needed in many delta regions to protect them from high tides, storm surges and salt water intrusion such as in the Red River Delta. The dyke system regulates the discharge and water exchange inside the diked area including irrigation channels for the paddy rice production. Local authorities observed increasing pollution towards the sea (highest pollution close to the dykes) and hypothesized that the dyke system would prevent water exchange and thus lead to an accumulation of pollutants within the diked area. Hence, the purpose of this study was to investigate the effect of dykes on pesticide pollution patterns in coastal delta regions of the Red River Delta. The study was conducted in the district Giao Thuy of the Red River Delta, Vietnam. This area is surrounded by a sea and river dyke; both have several inlet and outlet gates to control the water level in the irrigation channels. We determined the pesticide pollution pattern in a diked agricultural area, as well as along salinity gradients in and outside the diked areas. Samples were taken from rice fields and sediments from irrigation channels inside the diked area as well from saline aquaculture fields located outside the dyke. Pesticide analysis was conducted by accelerated solvent extraction (ASE), followed up by the clean-up process described by Laabs et al. (2007) and analyses using gas chromatography coupled with a mass selective detector (MSD). Preliminary results suggest that out of the 26 analysed compounds chlorpyrifos, propiconazole and

Abundance and patterns of transparent exopolymer particles (TEP) in Arctic floodplain lakes of the Mackenzie River Delta

NASA Astrophysics Data System (ADS)

Chateauvert, C. Adam; Lesack, Lance F. W.; Bothwell, Max L.

2012-12-01

The Mackenzie River Delta is a lake-rich arctic floodplain that receives high inputs of dissolved organic matter (DOM) and suspended particulates from allochthonous and autochthonous sources, and may transfer carbon from dissolved to particulate phase via in situ formation of transparent exopolymer particles (TEP). TEP provides food for grazers, surfaces for bacteria, and increased potential for aggregation and sedimentation of organic matter. During open water 2006, we tracked TEP abundances in three Delta lakes representing gradients that include declining river-to-lake connection times, increasing levels of dissolved organic carbon (DOC), and declining chromophoric-DOM (CDOM). Unexpectedly, TEP abundances were highest immediately after the flood, when autochthonous autotrophic production was at a seasonal low and CDOM a seasonal high. Moreover, the lake with the strongest riverine influence and lowest levels of autochthonous autotrophic production had the highest mean TEP-carbon (TEP-C) concentrations among the lakes. The mean proportion of particulate organic carbon (POC) represented by TEP-C increased with increasing river connection time, and appears to represent a substantial proportion of POC in Mackenzie Delta Lakes. Unexpectedly, the TEP gradient was most strongly related to CDOM (river water source) rather than overall DOC. Variations in CDOM accounted for 53% of TEP-C variation among the lakes, indicating allochthonous matter was the most important source of TEP. DOC release from in situ macrophytes during periods of high photosynthesis may contribute to TEP formation in the lake with lowest riverine influence, but pH levels >9.5 driven by the high photosynthetic rates complicate the interpretation of results from this lake.

Inversion and Prediction of Consolidation Settlement Characteristics of the Fluvial Sediments Based on Void Ratio Variation in the Northern Modern Yellow River Subaqueous Delta, China

NASA Astrophysics Data System (ADS)

Liu, Xiao; Liu, Jie; Feng, Xiuli

2018-06-01

The modern Yellow River delta is formed near the estuary of the Yellow River with the characteristics of short formation time, efficient sedimentation rate and loose structure which make sediments prone to be compacted and consolidate under the geostatic stress and overburden stress. It is one of the key areas with land subsidence disasters in China, bringing a series of safety hazards to production and living. Based on the data of massive surface cores and ten drill holes ranging from 12 to 40 m obtained from the northern modern Yellow River subaqueous delta, the inversion method suitable for the calculation of consolidation settlement characteristics of the modern Yellow River subaqueous delta is discussed, and the consolidation settlement characteristics of the delta sediments are inversed and predicted in this paper. The actual void ratio of the delta sediments at the depth from 3 to 15 m shows a significant power function relationship with the depth, while the void ratio of the sediments below 15 m changes little with depth. The pre-consolidation settlement (from deposition to sampling) of the delta sediments is between 0.91 and 1.96 m, while the consolidation settlement of unit depth is between 9.6 and 14.0 cm m-1. The post-consolidation settlement (from sampling to stable) of the subaqueous delta sediments is between 0.65 and 1.56 m in the later stage, and the consolidation settlement of unit depth is between 7.6 and 13.1 cm m-1 under the overburden stress. The delta sediments with a buried depth of 3 to 7 m contribute the most to the possible consolidation settlement in the later stage.

Man made deltas

PubMed Central

Maselli, Vittorio; Trincardi, Fabio

2013-01-01

The review of geochronological and historical data documents that the largest southern European deltas formed almost synchronously during two short intervals of enhanced anthropic pressure on landscapes, respectively during the Roman Empire and the Little Ice Age. These growth phases, that occurred under contrasting climatic regimes, were both followed by generalized delta retreat, driven by two markedly different reasons: after the Romans, the fall of the population and new afforestation let soil erosion in river catchments return to natural background levels; since the industrial revolution, instead, flow regulation through river dams overkill a still increasing sediment production in catchment basins. In this second case, furthermore, the effect of a reduced sediment flux to the coasts is amplified by the sinking of modern deltas, due to land subsidence and sea level rise, that hampers delta outbuilding and increases the vulnerability of coastal zone to marine erosion and flooding. PMID:23722597

Ganges-Brahmaputra Delta: Balance of Subsidence, Sea level and Sedimentation in a Tectonically-Active Delta (Invited)

NASA Astrophysics Data System (ADS)

Steckler, M. S.; Goodbred, S. L.; Akhter, S. H.; Seeber, L.; Reitz, M. D.; Paola, C.; Nooner, S. L.; DeWolf, S.; Ferguson, E. K.; Gale, J.; Hossain, S.; Howe, M.; Kim, W.; McHugh, C. M.; Mondal, D. R.; Petter, A. L.; Pickering, J.; Sincavage, R.; Williams, L. A.; Wilson, C.; Zumberge, M. A.

2013-12-01

Bangladesh is vulnerable to a host of short and long-term natural hazards - widespread seasonal flooding, river erosion and channel avulsions, permanent land loss from sea level rise, natural groundwater arsenic, recurrent cyclones, landslides and huge earthquakes. These hazards derive from active fluvial processes related to the growth of the delta and the tectonics at the India-Burma-Tibet plate junctions. The Ganges and Brahmaputra rivers drain 3/4 of the Himalayas and carry ~1 GT/y of sediment, 6-8% of the total world flux. In Bangladesh, these two great rivers combine with the Meghna River to form the Ganges-Brahmaputra-Meghna Delta (GBMD). The seasonality of the rivers' water and sediment discharge is a major influence causing widespread flooding during the summer monsoon. The mass of the water is so great that it causes 5-6 cm of seasonal elastic deformation of the delta discerned by our GPS data. Over the longer-term, the rivers are also dynamic. Two centuries ago, the Brahmaputra River avulsed westward up to 100 km and has since captured other rivers. The primary mouth of the Ganges has shifted 100s of km eastward from the Hooghly River over the last 400y, finally joining the Brahmaputra in the 19th century. These avulsions are influenced by the tectonics of the delta. On the east side of Bangladesh, the >16 km thick GBMD is being overridden by the Burma Arc where the attempted subduction of such a thick sediment pile has created a huge accretionary prism. The foldbelt is up to 250-km wide and its front is buried beneath the delta. The main Himalayan thrust front is <100 km north, but adjacent to the GBMD is the Shillong Massif, a 300-km long, 2-km high block of uplifted Indian basement that is overthrusting and depressing GBMD sediments to the south. The overthrusting Shillong Massif may represent a forward jump of the Himalayan front to a new plate boundary. This area ruptured in a ~M8 1897 earthquake. Subsidence from the tectonics and differential

Classification of community types, successional sequences, and landscapes of the Copper River Delta, Alaska.

Treesearch

Keith. Boggs

2000-01-01

A classification of community types, successional sequences, and landscapes is presented for the piedmont of the Copper River Delta. The classification was based on a sampling of 471 sites. A total of 75 community types, 42 successional sequences, and 6 landscapes are described. The classification of community types reflects the existing vegetation communities on the...

River, delta and coastal morphological response accounting for biological dynamics

NASA Astrophysics Data System (ADS)

Goldsmith, W.; Bernardi, D.; Schippa, L.

2015-03-01

Management and construction can increase resilience in the face of climate change, and benefits can be enhanced through integration of biogenic materials including shells and vegetation. Rivers and coastal landforms are dynamic systems that respond to intentional and unintended manipulation of critical factors, often with unforeseen and/or undesirable resulting effects. River management strategies have impacts that include deltas and coastal areas which are increasingly vulnerable to climate change with reference to sea level rise and storm intensity. Whereas conventional assessment and analysis of rivers and coasts has relied on modelling of hydrology, hydraulics and sediment transport, incorporating additional biological factors can offer more comprehensive, beneficial and realistic alternatives. Suitable modelling tools can provide improved decision support. The question has been whether current models can effectively address biological responses with suitable reliability and efficiency. Since morphodynamic evolution exhibits its effects on a large timescale, the choice of mathematical model is not trivial and depends upon the availability of data, as well as the spatial extent, timelines and computation effort desired. The ultimate goal of the work is to set up a conveniently simplified river morphodynamic model, coupled with a biological dynamics plant population model able to predict the long-term evolution of large alluvial river systems managed through bioengineering. This paper presents the first step of the work related to the application of the model accounting for stationary vegetation condition. Sensitivity analysis has been performed on the main hydraulic, sedimentology, and biological parameters. The model has been applied to significant river training in Europe, Asia and North America, and comparative analysis has been used to validate analytical solutions. Data gaps and further areas for investigation are identified.

The evolution of the River Nile. The buried saline rift lakes in Sudan—I. Bahr El Arab Rift, the Sudd buried saline lake

NASA Astrophysics Data System (ADS)

Salama, Ramsis B.

The River Nile in Sudan, was during the Tertiary, a series of closed lake basins. Each basin occupying one of the major Sudanese rift systems (Salama, 1985a). In this paper evidence is presented for the presence of the buried saline Sudd Lake in Bahr El Arab rift. The thick Tertiary sediments filling the deep grabens were eroded from the elevated blocks; Jebel Marra, Darfur Dome, Nuba Mountains and the Nile-Congo Divide. The thick carbonate deposits existing at the faulted boundaries of Bahr El Arab defines the possible boundaries between the fresh and saline water bodies. The widespread presence of kanker nodules in the sediments was a result of continuous efflorescence, leaching and evaporative processes. The highly saline zone in the central part of the Sudd was formed through the same processes with additional sulphate being added by the oxidation of the hydrogen sulphide gases emanating from the oil fields.

Offshore Deterioration in the Mekong Delta, Vietnam

NASA Astrophysics Data System (ADS)

Stattegger, K.; Unverricht, D.; Heinrich, C.

2016-02-01

The interplay of river, tide and wave forcing controls shape and sedimentation at the front of the Mekong Delta. Specific hydro- and morphodynamic conditions in the western subaqueous part of the asymmetric Mekong Delta generate a sand ridge - channel system (SRCS) which is unique in subaqueous delta formation. This large-scale morphological element extends 130 km along the delta front consisting of two sand ridges and two erosional channels. Three different zones within SRCS can be distinguished. The eastern initial zone stretches along delta slope and inner shelf platform southwest of the Bassac river mouth, the largest and westernmost distributary of the Mekong Delta. In the central zone SRCS covers the outer part of the subaqueous delta platform with a pronounced sand-ridge and erosional channel morphology. Cross-sections of the SRCS reveal an asymmetric shape including steeper ridge flanks facing into offshore direction. Channels incise down to 18.2 m water depth (wd) and 10.5 down the ridge top at the outer subaqueous delta platform, respectively. Towards the west the sand ridges pinch out while the two channels merge into one and form a giant erosional scour of up to 33 m wd within the subaqueous delta platform. In the western zone, the channel gets shallower and vanishes along the south-western edge of the subaqueous delta platform around Ca Mau Cape. Sediment transport from the Mekong River nourishes the sand ridges. In contrast, tide and wind-driven currents cut the erosional channels, which act also as fine-sediment conveyor from eroding headlands to the distal part of the delta front that is 200 km apart of the Bassac river mouth. SRCS in the subaqueous Mekong Delta is a relevant indicator of delta-front instability and erosion.

The Persian Gulf and the Delta of the Tigris and Euphrates Rivers, Kuwait, Iraq, and Iran

NASA Image and Video Library

2008-09-04

This image from NASA EarthKAM is of the northern end of the Persian Gulf and the broad delta complex of the Tigris, Euphrates, Shatt al Arab, and Karun rivers has captured the arid-looking wetlands of northeast Kuwait Bubiyan Island,

The changing hydro-ecological dynamics of rivers and deltas of the Western Indian Ocean: Anthropogenic and environmental drivers, local adaptation and policy response

NASA Astrophysics Data System (ADS)

Duvail, Stéphanie; Hamerlynck, Olivier; Paron, Paolo; Hervé, Dominique; Nyingi, Wanja D.; Leone, Michele

2017-10-01

The rivers flowing into the Western Indian Ocean have steep headwater gradients and carry high sediment loads. In combination with strong tides and seasonal rainfall, these rivers create dynamic deltas with biodiversity-rich and productive ecosystems that, through flooding, have sustained indigenous use systems for centuries. However, river catchments are rapidly changing due to deforestation. Hydropower dams also increasingly alter flood characteristics, reduce sediment supply and contribute to coastal erosion. These impacts are compounded by climate change. Altogether, these changes affect the livelihoods of the delta users. Here, based on prior works that we and others have conducted in the region, we analyse the drivers of these hydro-ecological changes. We then provide recommendations for improved dam design and operations to sustain the underlying delta-building processes, the ecosystem values and the needs of the users.

[Integrated assessment of eco-environmental vulnerability in Pearl River Delta based on RS and GIS].

PubMed

Xu, Qing-Yong; Huang, Mei; Liu, Hong-Sheng; Yan, Hui-Min

2011-11-01

Based on the remote sensing data and with the help of geographic information system, an integrated assessment was conducted on the eco-environmental vulnerability of Pearl River Delta in 2004-2008. Spatial principal component analysis was used to generate the evaluation indicators, and analytic hierarchy process (AHP) was applied to determine the weights of the evaluation factors. The reasons causing the vulnerability of the eco- environment in Pearl River Delta were discussed. In the study area, its middle part was the most vulnerable region, occupying 34.0% of the total, eastern part was the moderately vulnerable region, accounting for 25.5%, and western part was the lightly and slightly vulnerable areas, accounting for 28.7 and 11.8%, respectively. Totally, the moderately and lightly vulnerable areas occupied 54.2%, indicating that a majority of the Delta was under moderate and light vulnerability. The natural factors affecting the eco-environmental vulnerability of the Delta were altitude, heavy rain days, water and soil erosion rate, flooded infield rate, normalized difference vegetation index (ND VI) and landscape diversity index, whereas the human factors were population density, waste discharge per unit area, exhaust emission per unit area, land use change, chemical fertilization intensity, pesticide application intensity, amount of motor vehicles possessed by ten thousands people, and index of environmental protection investment. The main characteristics of the extremely and heavily vulnerable regions were low altitude, high frequency of flood disaster, large flooded infield, serious vegetation degradation, high pollution level and low environment protection investment index.

Sediment Trapping Pathways and Mechanisms through the Mekong Tidal River and Subaqueous Delta

DTIC Science & Technology

2013-09-30

strive to understand how the delicate balance of ebb and flood sediment fluxes is maintained to create tidal flat and mangrove complexes, and...subaqueous delta on the inner continental shelf, and sediment sinks within vegetated/ mangrove shoreline complexes. Our overall hypothesis is that sediment... Mangrove /Vegetated Intertidal Areas. Along the main stem tidal river and coastal banks may be shorelines lined with vegetation ( mangroves at the

Response of the St. Joseph River to lake level changes during the last 12,000 years in the Lake Michigan basin

USGS Publications Warehouse

Kincare, K.A.

2007-01-01

The water level of the Lake Michigan basin is currently 177 m above sea level. Around 9,800 14C years B.P., the lake level in the Lake Michigan basin had dropped to its lowest level in prehistory, about 70 m above sea level. This low level (Lake Chippewa) had profound effects on the rivers flowing directly into the basin. Recent studies of the St. Joseph River indicate that the extreme low lake level rejuvenated the river, causing massive incision of up to 43 m in a valley no more than 1.6 km wide. The incision is seen 25 km upstream of the present shoreline. As lake level rose from the Chippewa low, the St. Joseph River lost competence and its estuary migrated back upstream. Floodplain and channel sediments partially refilled the recently excavated valley leaving a distinctly non-classical morphology of steep sides with a broad, flat bottom. The valley walls of the lower St. Joseph River are 12-18 m tall and borings reveal up to 30 m of infill sediment below the modern floodplain. About 3 ?? 108 m3 of sediment was removed from the St. Joseph River valley during the Chippewa phase lowstand, a massive volume, some of which likely resides in a lowstand delta approximately 30 km off-shore in Lake Michigan. The active floodplain below Niles, Michigan, is inset into an upper terrace and delta graded to the Calumet level (189 m) of Lake Chicago. In the lower portion of the terrace stratigraphy a 1.5-2.0 m thick section of clast-supported gravel marks the entry of the main St. Joseph River drainage above South Bend, Indiana, into the Lake Michigan basin. This gravel layer represents the consolidation of drainage that probably occurred during final melting out of ice-marginal kettle chains allowing stream piracy to proceed between Niles and South Bend. It is unlikely that the St. Joseph River is palimpsest upon a bedrock valley. The landform it cuts across is a glaciofluvial-deltaic feature rather than a classic unsorted moraine that would drape over pre-glacial topography

Surface-ground water interactions and hydrogeochemical evolution in a fluvio-deltaic setting: The case study of the Pinios River delta

NASA Astrophysics Data System (ADS)

Matiatos, Ioannis; Paraskevopoulou, Vasiliki; Lazogiannis, Konstantinos; Botsou, Fotini; Dassenakis, Manos; Ghionis, George; Alexopoulos, John D.; Poulos, Serafim E.

2018-06-01

River deltas sustain important ecosystems with rich biodiversity and large biomass, as well as human populations via the availability of water and food sources. Anthropogenic activities, such as urbanization, tourism and agriculture, may pose threats to river deltas. The knowledge of the factors controlling the regional water quality regime in these areas is important for planning sustainable use and management of the water resources. Here, hydrochemical methods and multivariate statistical techniques were combined to investigate the shallow aquifer of the Pinios River (Thessaly) deltaic plain with respect to water quality, hydrogeochemical evolution and interactions between groundwater and surface water bodies. Water quality assessment indicated that most of the river and groundwater samples fully comply with the criteria set by the Drinking Water Directive (98/83/EC). The river is recharged mainly from springs of the Tempi valley and the shallow aquifer, and to a lesser degree from precipitation, throughout the year. The hydrogeochemical characteristics indicated a cation (Ca, Mg, and Na) bicarbonate water type, which evolves to calcium-chloride, sodium-bicarbonate and sodium-chloride water type, in the northern part of the delta. Calcite and dolomite dissolution determined the major ion chemistry, but other processes, such as silicate weathering and cation exchange reactions, also contributed. In the northern part of the plain, the interaction with the deeper aquifer enriched the shallow aquifer with Na and Cl ions. Principal Component Analysis showed that five components (PCs) explain 77% of the total variance of water quality parameters; these are: (1) salinity; (2) water-silicate rocks interaction; (3) hardness due to calcite dissolution, and cation exchange processes; (4) nitrogen pollution; and (5) non-N-related artificial fertilizers. This study demonstrated that the variation of water hydrochemistry in the deltaic plain could be attributed to natural and

Soil properties of mangroves in contrasting geomorphic settings within the Zambezi River Delta, Mozambique

Treesearch

Christina E. Stringer; Carl C. Trettin; Stan Zarnoch

2016-01-01

Mangroves are well-known for their numerous ecosystem services, including sequestering a significant carbon stock, with soils accounting for the largest pool. The soil carbon pool is dependent on the carbon content and bulk density. Our objective was to assess the spatial variability of mangrove soil physical and chemical properties within the Zambezi River Delta and...

Sediment infilling and wetland formation dynamics in an active crevasse splay of the Mississippi River delta

USGS Publications Warehouse

Cahoon, Donald R.; White, David A.; Lynch, James C.

2011-01-01

Crevasse splay environments provide a mesocosm for evaluating wetland formation and maintenance processes on a decadal time scale. Site elevation, water levels, vertical accretion, elevation change, shallow subsidence, and plant biomass were measured at five habitats along an elevation gradient to evaluate wetland formation and development in Brant Pass Splay; an active crevasse splay of the Balize delta of the Mississippi River. The processes of vertical development (vertical accretion, elevation change, and shallow subsidence) were measured with the surface elevation table–marker horizon method. There were three distinct stages to the accrual of elevation capital and wetland formation in the splay: sediment infilling, vegetative colonization, and development of a mature wetland community. Accretion, elevation gain, and shallow subsidence all decreased by an order of magnitude from the open water (lowest elevation) to the forest (highest elevation) habitats. Vegetative colonization occurred within the first growing season following emergence of the mud surface. An explosively high rate of below-ground production quickly stabilized the loosely consolidated sub-aerial sediments. After emergent vegetation colonization, vertical development slowed and maintenance of marsh elevation was driven both by sediment trapping by the vegetation and accumulation of plant organic matter in the soil. Continued vertical development and survival of the marsh then depended on the health and productivity of the plant community. The process of delta wetland formation is both complex and nonlinear. Determining the dynamics of wetland formation will help in understanding the processes driving the past building of the delta and in developing models for restoring degraded wetlands in the Mississippi River delta and other deltas around the world.

Sources, bioavailability, and photoreactivity of dissolved organic carbon in the Sacramento-San Joaquin River Delta

USGS Publications Warehouse

Stepanauskas, R.; Moran, M.A.; Bergamaschi, B.A.; Hollibaugh, J.T.

2005-01-01

We analyzed bioavailability, photoreactivity, fluorescence, and isotopic composition of dissolved organic carbon (DOC) collected at 13 stations in the Sacramento-San Joaquin River Delta during various seasons to estimate the persistence of DOC from diverse shallow water habitat sources. Prospective large-scale wetland restorations in the Delta may change the amount of DOC available to the food web as well as change the quality of Delta water exported for municipal use. Our study indicates that DOC contributed by Delta sources is relatively refractory and likely mostly the dissolved remnants of vascular plant material from degrading soils and tidal marshes rather than phytoplankton production. Therefore, the prospective conversion of agricultural land into submerged, phytoplankton-dominated habitats may reduce the undesired export of DOC from the Delta to municipal users. A median of 10% of Delta DOC was rapidly utilizable by bacterioplankton. A moderate dose of simulated solar radiation (286 W m-2 for 4 h) decreased the DOC bioavailability by an average of 40%, with a larger relative decrease in samples with higher initial DOC bioavailability. Potentially, a DOC-based microbial food web could support ???0.6 ?? 109 g C of protist production in the Delta annually, compared to ???17 ?? 109 g C phytoplankton primary production. Thus, DOC utilization via the microbial food web is unlikely to play an important role in the nutrition of Delta zooplankton and fish, and the possible decrease in DOC concentration due to wetland restoration is unlikely to have a direct effect on Delta fish productivity. ?? Springer 2005.

How Rapid Change Affects Deltas in the Arctic Region

NASA Astrophysics Data System (ADS)

Overeem, I.; Bendixen, M.

2017-12-01

Deltas form where the river drains into the ocean. Consequently, delta depositional processes are impacted by either changes in the respective river drainage basin or by changes in the regional marine environment. In a warming Arctic region rapid change has occurred over the last few decades in both the terrestrial domain as well as in the marine domain. Important terrestrial controls include 1) change in permafrost possibly destabilizing river banks, 2) strong seasonality of river discharge due to a short melting season, 3) high sediment supply if basins are extensively glaciated, 4) lake outbursts and ice jams favoring river flooding. Whereas in the Arctic marine domain sea ice loss promotes wave and storm surge impact, and increased longshore transport. We here ask which of these factors dominate any morphological change in Arctic deltas. First, we analyze hydrological data to assess change in Arctic-wide river discharge characteristics and timing, and sea ice concentration data to map changes in sea ice regime. Based on this observational analysis we set up a number of scenarios of change. We then model hypothetical small-scale delta formation considering change in these primary controls by setting up a numerical delta model, and combining it dynamically with a permafrost model. We find that for typical Greenlandic deltas changes in river forcing due to ice sheet melt dominate the morphological change, which is corroborated by mapping of delta progradation from aerial photos and satellite imagery. Whereas in other areas, along the North Slope and the Canadian Arctic small deltas are more stable or experienced retreat. Our preliminary coupled model allows us to further disentangle the impact of major forcing factors on delta evolution in high-latitude systems.

Human induced discharge diversion in a tropical delta and its environmental implications: The Patía River, Colombia

NASA Astrophysics Data System (ADS)

Restrepo, Juan D.; Kettner, Albert

2012-03-01

SummaryThe Patía River, the number one in terms of sediment yield ˜1500 t km-2 yr-1 draining the western South America, has the most extensive and well developed delta on the Pacific coast, measuring 1700 km2. During the Holocene, nature forced the Patía delta to the south; however, a major water diversion, starting in 1972, diverted the Patía flow to the Sanguianga River, the latter, a small stream draining internal lakes from the Pacific lowlands. This human induced discharge diversion shifted the active delta plain back to the north and changed the northern estuarine system into an active delta plain. Overall, major environmental consequences of this discharge diversion in terms of morphological changes along the delta coast and distributary channels, are evidenced by: (1) coastal retreat along the abandoned delta lobe; 63% of the southern shoreline is retreating at maximum rates of 7 m yr-1, with a corresponding coastal land loss of 106 m yr-1; (2) transgressive barrier islands with exposed peat soils in the surf zone; (3) abandonment of former active distributaries in the southern delta plain with associated closing of inlets and formation of ebb tidal deltas; (4) breaching events on barrier islands; and (5) distributary channel accretion in the northern delta plain by morphological processes such as sedimentation (also in crevasses), overbank flow, increasing width of levees, interdistributary channel fill, and colonization of pioneer mangrove. The Sanguianga Mangrove National Park (SMNP), the largest mangrove reserve in Colombia, measuring 800 km2, lies in this former estuary, where major hydrologic and sedimentation changes are occurring. Observed environmental changes in the SMNP, include (1) seaward advance of the sub-aqueous delta front at the Sanquianga inlet evidenced by an increase in tidal flat area from 5.4 Mm2 in 1986 to 14 Mm2 in 2001; (2) freshening conditions in the Sanguianga distributary channel, a hydrologic change that has shifted the

Prediction of villages at risk for filariasis transmission in the Nile Delta using remote sensing and geographic information system technologies.

PubMed

Hassan, A N; Beck, L R; Dister, S

1998-04-01

Remote sensing and geographic information system (GIS) technologies were used to discriminate between 130 villages, in the Nile Delta, at high and low risk for filariasis, as defined by microfilarial prevalence. Landsat Thematic Mapper (TM) data were digitally processed to generate a map of landcover as well as spectral indices such as NDVI and moisture index. A Tasseled Cap transformation was also carried out on the TM data which produced three more indices: brightness, greenness and wetness. GIS functions were used to extract information on landcover and spectral indices within one km buffers around the study villages. The relationship between satellite data and prevalence was investigated using discriminant analysis. The analysis indicated that the most important landscape elements associated with prevalence were water and marginal vegetation, while wetness and moisture index were the most important indices. Discriminant functions generated for these variables were able to correctly predict 80% and 74% of high and low prevalence villages, respectively, with an overall accuracy of 77%. The present approach provides a promising tool for regional filariasis surveillance and helps direct control efforts.

Geochronology of Mudflow Deposits on the Mississippi River Delta Front, Louisiana, USA

NASA Astrophysics Data System (ADS)

Keller, G. P.; Bentley, S. J.; Xu, K.; Georgiou, I. Y.; Miner, M. D.; Obelcz, J.; Maloney, J. M.

2016-02-01

Short multicores (<50cm) and longer gravity cores (up to 3m) were collected seaward of the Southwest Pass of the Mississippi River Delta (Gulf of Mexico) and were analyzed to assess the frequency, extent, and potential causes of submarine mass wasting events. Cores were analyzed for radionuclide activity, grain size, and density at 2cm resolution, with x-radiography for the whole core. Short-term sedimentation rates calculated from 7Be are 2-12cm/y, while longer-term accumulation from 210Pb are only 1.3-5.5cm/y. In most cores, 210Pb activity steadily decreases downcore without displaying a "stairstep" nature. However, six cores have layers of low 210Pb activity stratigraphically above layers with higher activity. In one long core from a mudflow gully, 210Pb steadily decreases for the upper 90cm before stabilizing for the remaining 130cm. Clay content generally ranges between 25-40% and sand ranges between 5-15% with silt making up the rest of each sample. Sedimentation rates derived from 210Pb in the short cores indicate that proximity to the river mouth has stronger influence than depositional environment (mudflow gully, depositional lobe, prodelta). This finding may be explained by rapid sedimentation rates coupled with a reduced tropical cyclone activity over the delta in the last seven years (2006-2013). The regions of decreased 210Pb activity may be evidence of scavenging effects of plume sedimentation because they do not correspond with decreases in clay fraction. The zone of homogenized activity below 90cm in the gully core occurs at a depth equivalent to 18 years, indicating mixing on a decadal scale, potentially from mudflows. These results may be explained by a lack of recent mass failures corresponding with lulls in tropical cyclone activity over the delta, preceded by a period of more active hurricane-driven mudflow activity.

Impact of anthropogenic activities on water quality and plankton communities in the Day River (Red River Delta, Vietnam).

PubMed

Hoang, Hang Thi Thu; Duong, Thi Thuy; Nguyen, Kien Trung; Le, Quynh Thi Phuong; Luu, Minh Thi Nguyet; Trinh, Duc Anh; Le, Anh Hung; Ho, Cuong Tu; Dang, Kim Dinh; Némery, Julien; Orange, Didier; Klein, Judith

2018-01-08

Planktons are a major component of food web structure in aquatic ecosystems. Their distribution and community structure are driven by the combination and interactions between physical, chemical, and biological factors within the environment. In the present study, water quality and the community structure of phytoplankton and zooplankton were monthly investigated from January to December 2015 at 11 sampling sites along the gradient course of the Day River (Red River Delta, northern Vietnam). The study demonstrated that the Day River was eutrophic with the average values of total phosphorus concentration 0.17 mg/L, total nitrogen concentration 1.98 mg/L, and Chl a 54 μg/L. Microscopic plankton analysis showed that phytoplankton comprised 87 species belonging to seven groups in which Chlorophyceae, Bacillariophyceae, and Cyanobacteria accounted for the most important constituents of the river's phytoplankton assemblage. A total 53 zooplankton species belonging to three main groups including Copepoda, Cladocera, and Rotatoria were identified. Plankton biomass values were greatest in rainy season (3002.10-3 cell/L for phytoplankton and 12.573 individuals/m 3 for zooplankton). Using principal correspondence and Pearson correlation analyses, it was found that the Day River was divided into three main site groups based on water quality and characteristics of plankton community. Temperature and nutrients (total phosphorus and total nitrogen) are key factors regulating plankton abundance and distribution in the Day River.

Geoarchaeological research for Roman waterworks in the Rhine-Meuse river delta, the Netherlands

NASA Astrophysics Data System (ADS)

Verhagen, Jan; Kluiving, Sjoerd; van Leeuwen, Liz; Anker, Emiel

2015-04-01

It is known that Romans in the Low Countries at the northern margin of their empire were practicing diverse systems of water state management to maintain economic and above all strategic stability. In early Roman period Romans created a shipping route from the Rhine towards the north by digging canals and constructing dams. This was done in order to submit the northern part of Germania through the Waddenzee and the German rivers Eems, Weser and Elbe. During the middle Roman period the Romans had canceled their efforts to submit Germania. In that period we know the River Rhine as the limes, which not only was a borderline of the Roman empire, but can also be seen as a guarded transport route. The research area is situated in the eastern part of the Rhine-Meuse river valley/delta system. The area represents a highly dynamic geological history of erosion and deposition close to the river system's equilibrium point. In order to reconstruct the former landscape and investigate whether traces of Roman waterworks could be indicated or disproved geoarchaeological coring campaigns have been carried out with lithological, textural and palaeoecological analyses. The results of the research presented in this poster will be: 1) Assessment of the condition of the covered Pleistocene sediments in the area, 2) Identification of the buried gullies and levees in the vicinity of the remains of the Roman castellum 'Carvium ad molem', which should have been built at the bifurcation of the delta branches of Rhine and Waal, 3) Chronological control of gullies and levees, 4) Landscape reconstruction in different time periods. Finally based on the geoarchaeological results a comment will be made on the location of the Drusus dam in the study area, the landscape context of the castellum and its position on the apex of the Insula Batavorum.

Development of a global river-coastal coupling model and its application to flood simulation in Asian mega-delta regions

NASA Astrophysics Data System (ADS)

Ikeuchi, Hiroaki; Hirabayashi, Yukiko; Yamazaki, Dai; Muis, Sanne; Ward, Philip; Verlaan, Martin; Winsemius, Hessel; Kanae, Shinjiro

2017-04-01

The world's mega-delta regions and estuaries are susceptible to various water-related disasters, such as river flooding and storm surge. Moreover, simultaneous occurrence of them would be more devastating than a situation where they occur in isolation. Therefore, it is important to provide information about compound risks of fluvial and coastal floods at a large scale, both their statistical dependency as well as their combined resulting flooding in delta regions. Here we report on a first attempt to address this issue globally by developing a method to couple a global river model (CaMa-Flood) and a global tide and surge reanalysis (GTSR) dataset. A state-of-the-art global river routing model, CaMa-Flood, was modified to represent varying sea levels due to tides and storm surges as downstream boundary condition, and the GTSR dataset was post-processed to serve as inputs to the CaMa-Flood river routing simulation and a long-term simulation was performed to incorporate the temporal dependency between coastal tide and surge on the one hand, and discharge on the other. The coupled model was validated against observations, showing better simulation results of water levels in deltaic regions than simulation without GTSR. For example in the Ganges Delta, correlation coefficients were increased by 0.06, and root mean square errors were reduced by 0.22 m. Global coupling simulations revealed that storm surges affected river water levels in coastal regions worldwide, especially in low-lying flat areas with increases in water level larger than 0.5 m. By employing enhanced storm surge simulation with tropical storm tracks, we also applied the model to examine impacts of past hurricane and cyclone storm events on river flood inundation.

Optimality and self-organization in river deltas

NASA Astrophysics Data System (ADS)

Tejedor, A.; Longjas, A.; Edmonds, D. A.; Zaliapin, I. V.; Georgiou, T. T.; Rinaldo, A.; Foufoula-Georgiou, E.

2017-12-01

Deltas are nourished by channel networks, whose connectivity constrains, if not drives, the evolution, functionality and resilience of these systems. Understanding the coevolution of deltaic channels and their flux organization is crucial for guiding maintenance strategies of these highly stressed systems from a range of anthropogenic activities. However, in contrast to tributary channel networks, to date, no theory has been proposed to explain how deltas self-organize to distribute water and sediment to the delta top and the shoreline. Here, we hypothesize the existence of an optimality principle underlying the self-organized partition of fluxes in delta channel networks. Specifically, we hypothesize that deltas distribute water and sediment fluxes on a given delta topology such as to maximize the diversity of flux delivery to the shoreline. By introducing the concept of nonlocal Entropy Rate (nER) and analyzing ten field deltas in diverse environments, we present evidence that supports our hypothesis, suggesting that delta networks achieve dynamically accessible maxima of their nER. Furthermore, by analyzing six simulated deltas using the Delf3D model and following their topologic and flux re-organization before and after major avulsions, we further study the evolution of nER and confirm our hypothesis. We discuss how optimal flux distributions in terms of nER, when interpreted in terms of resilience, are configurations that reflect an increased ability to withstand perturbations.

Fractionation and ecological risk of metals in urban river sediments in Zhongshan City, Pearl River Delta.

PubMed

Cai, Jiannan; Cao, Yingzi; Tan, Haijian; Wang, Yanman; Luo, Jiaqi

2011-09-01

Surface sediments collected from nine urban rivers located in Zhongshan City, Pearl River Delta, were analyzed for total concentration of metals with digestion and chemical fractionation adopting the modified European Community Bureau of Reference (BCR) sequential extraction procedure. The results showed that concentration and fractionation of metals varied significantly among the rivers. The total concentration of eight metals in most rivers did not exceed the China Environmental Quality Standard for Soil, Grade III. The potential ecological risk of metals to rivers were related to the land use patterns, in the order of manufacturing areas > residential areas > agriculture areas. The concentration of Pb in the reducible fraction was relatively high (60.0-84.3%). The dominant proportions of Cd, Zn and Cu were primary in the non-residual fraction (67.0%, 71.8% and 81.4% on average respectively), while the percentages of the residual fractions of Cr and Ni varied over a wide range (43-85% and 24-71% respectively). The approaches of the Håkanson ecological risk index and Secondary Phase Enrichment Factor were applied for ecological risk assessment and metal enrichment calculation. The results indicated Hg and Cd had posed high potential ecological risk to urban rivers in this region. Meanwhile, there was widespread pollution and high enrichment of Cu in river sediments in this region. Multiple regression analysis showed that five water quality parameters (pH, DO, COD(Mn), NH(4)(+)-N, TP) had little influence on the distribution of metal fractionation. This result revealed that the ecological risk of metals was not eliminated along with the improvement in water quality. Correlation studies showed that among the metals, Group A (Cd, As, Pb, Zn Hg, r = 0.730-0.924) and Group B (Cr, Cu, Ni, r = 0.815-0.948) were obtained, and the metal contaminations were from industrial activities rather than residential.

Water balance dynamics in the Nile Basin

USGS Publications Warehouse

Senay, Gabriel B.; Asante, Kwabena; Artan, Guleid A.

2009-01-01

Understanding the temporal and spatial dynamics of key water balance components of the Nile River will provide important information for the management of its water resources. This study used satellite-derived rainfall and other key weather variables derived from the Global Data Assimilation System to estimate and map the distribution of rainfall, actual evapotranspiration (ETa), and runoff. Daily water balance components were modelled in a grid-cell environment at 0·1 degree (∼10 km) spatial resolution for 7 years from 2001 through 2007. Annual maps of the key water balance components and derived variables such as runoff and ETa as a percent of rainfall were produced. Generally, the spatial patterns of rainfall and ETa indicate high values in the upstream watersheds (Uganda, southern Sudan, and southwestern Ethiopia) and low values in the downstream watersheds. However, runoff as a percent of rainfall is much higher in the Ethiopian highlands around the Blue Nile subwatershed. The analysis also showed the possible impact of land degradation in the Ethiopian highlands in reducing ETa magnitudes despite the availability of sufficient rainfall. Although the model estimates require field validation for the different subwatersheds, the runoff volume estimate for the Blue Nile subwatershed is within 7·0% of a figure reported from an earlier study. Further research is required for a thorough validation of the results and their integration with ecohydrologic models for better management of water and land resources in the various Nile Basin ecosystems.

Space Radar Image of Mississippi Delta

NASA Image and Video Library

1999-04-15

This is a radar image of the Mississippi River Delta where the river enters into the Gulf of Mexico along the coast of Louisiana. This multi-frequency image demonstrates the capability of the radar to distinguish different types of wetlands surfaces in river deltas. This image was acquired by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the space shuttle Endeavour on October 2, 1995. The image is centered on latitude 29.3 degrees North latitude and 89.28 degrees West longitude. The area shown is approximately 63 kilometers by 43 kilometers (39 miles by 26 miles). North is towards the upper right of the image. As the river enters the Gulf of Mexico, it loses energy and dumps its load of sediment that it has carried on its journey through the mid-continent. This pile of sediment, or mud, accumulates over the years building up the delta front. As one part of the delta becomes clogged with sediment, the delta front will migrate in search of new areas to grow. The area shown on this image is the currently active delta front of the Mississippi. The migratory nature of the delta forms natural traps for oil and the numerous bright spots along the outside of the delta are drilling platforms. Most of the land in the image consists of mud flats and marsh lands. There is little human settlement in this area due to the instability of the sediments. The main shipping channel of the Mississippi River is the broad red stripe running northwest to southeast down the left side of the image. The bright spots within the channel are ships. The colors in the image are assigned to different frequencies and polarizations of the radar as follows: red is L-band vertically transmitted, vertically received; green is C-band vertically transmitted, vertically received; blue is X-band vertically transmitted, vertically received. http://photojournal.jpl.nasa.gov/catalog/PIA01784

Urban Household Carbon Emission and Contributing Factors in the Yangtze River Delta, China

PubMed Central

Xu, Xibao; Tan, Yan; Chen, Shuang; Yang, Guishan; Su, Weizhong

2015-01-01

Carbon reduction at the household level is an integral part of carbon mitigation. This study analyses the characteristics, effects, contributing factors and policies for urban household carbon emissions in the Yangtze River Delta of China. Primary data was collected through structured questionnaire surveys in three cities in the region – Nanjing, Ningbo, and Changzhou in 2011. The survey data was first used to estimate the magnitude of household carbon emissions in different urban contexts. It then examined how, and to what extent, each set of demographic, economic, behavioral/cognitive and spatial factors influence carbon emissions at the household level. The average of urban household carbon emissions in the region was estimated to be 5.96 tonnes CO2 in 2010. Energy consumption, daily commuting, garbage disposal and long-distance travel accounted for 51.2%, 21.3%, 16.0% and 11.5% of the total emission, respectively. Regulating rapidly growing car-holdings of urban households, stabilizing population growth, and transiting residents’ low-carbon awareness to household behavior in energy saving and other spheres of consumption in the context of rapid population aging and the growing middle income class are suggested as critical measures for carbon mitigation among urban households in the Yangtze River Delta. PMID:25884853

Analysis of the Sediment Hydrograph of the alluvial deltas in the Apalachicola River, Florida

NASA Astrophysics Data System (ADS)

Daranpob, A.; Hagen, S.; Passeri, D.; Smar, D. E.

2011-12-01

Channel and alluvial characteristics in lowlands are the products of boundary conditions and driving forces. The boundary conditions normally include materials and land cover types, such as soil type and vegetation cover. General driving forces include discharge rate, sediment loadings, tides and waves. Deltas built up of river-transported sediment occur in depositional zones of the river mouth in flat terrains and slow currents. Total sediment load depends on two major abilities of the river, the river shear stress and capacity. The shear stress determines transport of a given sediment grain size, normally expressed as tractive force. The river capacity determines the total load or quantity of total sediments transported across a section of the river, generally expressed as the sediment loading rate. The shear stress and sediment loading rate are relatively easy to measure in the headwater and transfer zones where streams form a v-shape valley and the river begins to form defined banks compared to the deposition zone where rivers broaden across lower elevation landscapes creating alluvial forms such as deltas. Determinations of deposition and re-suspension of sediment in fluvial systems are complicated due to exerting tidal, wind, and wave forces. Cyclic forces of tides and waves repeatedly change the sediment transport and deposition rate spatially and temporally in alluvial fans. However, the influence decreases with water depth. Understanding the transport, deposition, and re-suspension of sediments in the fluvial zone would provide a better understanding of the morphology of landscape in lowland estuaries such as the Apalachicola Bay and its estuary systems. The Apalachicola River system is located in the Florida Panhandle. Shelf sedimentation process is not a strong influence in this region because it is protected by barrier islands from direct ocean forces of the Gulf of Mexico. This research explores the characteristic of suspended sediment loadings in

Recent coarsening of sediments on the southern Yangtze subaqueous delta front: A response to river damming

NASA Astrophysics Data System (ADS)

Yang, H. F.; Yang, S. L.; Meng, Y.; Xu, K. H.; Luo, X. X.; Wu, C. S.; Shi, B. W.

2018-03-01

After more than 50,000 dams were built in the Yangtze basin, especially the Three Gorges Dam (TGD) in 2003, the sediment discharge to the East China Sea decreased from 470 Mt/yr before dams to the current level of 140 Mt/yr. The delta sediment's response to this decline has interested many researchers. Based on a dataset of repeated samplings at 44 stations in this study, we compared the surficial sediment grain sizes in the southern Yangtze subaqueous delta front for two periods: pre-TGD (1982) and post-TGD (2012). External factors of the Yangtze River, including water discharge, sediment discharge and suspended sediment grain size, were analysed, as well as wind speed, tidal range and wave height of the coastal ocean. We found that the average median size of the sediments in the delta front coarsened from 8.0 μm in 1982 to 15.4 μm in 2012. This coarsening was accompanied by a decrease of clay components, better sorting and more positive skewness. Moreover, the delta morphology in the study area changed from an overall accretion of 1.0 cm/yr to an erosion of - 0.6 cm/yr. At the same time, the riverine sediment discharge decreased by 70%, and the riverine suspended sediment grain size increased from 8.4 μm to 10.5 μm. The annual wind speed and wave height slightly increased by 2% and 3%, respectively, and the tidal range showed no change trend. Considering the increased wind speed and wave height, there was no evidence that the capability of the China Coastal Current to transport sediment southward has declined in recent years. The sediment coarsening in the Yangtze delta front was thus mainly attributed to the delta's transition from accumulation to erosion which was originally generated by river damming. These findings have important implications for sediment change in many large deltaic systems due to worldwide human impacts.

Mapping Soil Carbon in the Yukon Kuskokwim River Delta Alaska

NASA Astrophysics Data System (ADS)

Natali, S.; Fiske, G.; Schade, J. D.; Mann, P. J.; Holmes, R. M.; Ludwig, S.; Melton, S.; Sae-lim, N.; Jardine, L. E.; Navarro-Perez, E.

2017-12-01

Arctic river deltas are hotspots for carbon storage, occupying <1% of the pan-Arctic watershed but containing >10% of carbon stored in arctic permafrost. The Yukon Kuskokwim (YK) Delta, Alaska is located in the lower latitudinal range of the northern permafrost region in an area of relatively warm permafrost that is particularly vulnerable to warming climate. Active layer depths range from 50 cm on peat plateaus to >100 cm in wetland and aquatic ecosystems. The size of the soil organic carbon pool and vulnerability of the carbon in the YK Delta is a major unknown and is critically important as climate warming and increasing fire frequency may make this carbon vulnerable to transport to aquatic and marine systems and the atmosphere. To characterize the size and distribution of soil carbon pools in the YK Delta, we mapped the land cover of a 1910 km2 watershed located in a region of the YK Delta that was impacted by fire in 2015. The map product was the result of an unsupervised classification using the Weka K Means clustering algorithm implemented in Google's Earth Engine. Inputs to the classification were Worldview2 resolution optical imagery (1m), Arctic DEM (5m), and Sentinel 2 level 1C multispectral imagery, including NDVI, (10 m). We collected 100 soil cores (0-30 cm) from sites of different land cover and landscape position, including moist and dry peat plateaus, high and low intensity burned plateaus, fens, and drained lakes; 13 lake sediment cores (0-50 cm); and 20 surface permafrost cores (to 100 cm) from burned and unburned peat plateaus. Active layer and permafrost soils were analyzed for organic matter content, soil moisture content, and carbon and nitrogen pools (30 and 100 cm). Soil carbon content varied across the landscape; average carbon content values for lake sediments were 12% (5- 17% range), fens 26% (9-44%), unburned peat plateaus 41% (34-44%), burned peat plateaus 19% (7-34%). These values will be used to estimate soil carbon pools, which will

Beach morphology and change along the mixed grain-size delta of the dammed Elwha River, Washington

USGS Publications Warehouse

Warrick, J.A.; George, D.A.; Gelfenbaum, G.; Ruggiero, P.; Kaminsky, G.M.; Beirne, M.

2009-01-01

Sediment supply provides a fundamental control on the morphology of river deltas, and humans have significantly modified these supplies for centuries. Here we examine the effects of almost a century of sediment supply reduction from the damming of the Elwha River in Washington on shoreline position and beach morphology of its wave-dominated delta. The mean rate of shoreline erosion during 1939-2006 is ~ 0.6??m/yr, which is equivalent to ~ 24,000??m3/yr of sediment divergence in the littoral cell, a rate approximately equal to 25-50% of the littoral-grade sediment trapped by the dams. Semi-annual surveys between 2004 and 2007 show that most erosion occurs during the winter with lower rates of change in the summer. Shoreline change and morphology also differ spatially. Negligible shoreline change has occurred updrift (west) of the river mouth, where the beach is mixed sand to cobble, cuspate, and reflective. The beach downdrift (east) of the river mouth has had significant and persistent erosion, but this beach differs in that it has a reflective foreshore with a dissipative low-tide terrace. Downdrift beach erosion results from foreshore retreat, which broadens the low-tide terrace with time, and the rate of this kind of erosion has increased significantly from ~ 0.8??m/yr during 1939-1990 to ~ 1.4??m/yr during 1990-2006. Erosion rates for the downdrift beach derived from the 2004-2007 topographic surveys vary between 0 and 13??m/yr, with an average of 3.8??m/yr. We note that the low-tide terrace is significantly coarser (mean grain size ~ 100??mm) than the foreshore (mean grain size ~ 30??mm), a pattern contrary to the typical observation of fining low-tide terraces in the region and worldwide. Because this cobble low-tide terrace is created by foreshore erosion, has been steady over intervals of at least years, is predicted to have negligible longshore transport compared to the foreshore portion of the beach, and is inconsistent with oral history of abundant

Classification of Martian deltas

NASA Technical Reports Server (NTRS)

Dehon, R. A.

1993-01-01

Water-borne sediments in streams are deposited, upon eventual cessation of flow, either as deltas or as alluvial fans or plains. Deltas and alluvial fans share a common characteristic; both may be described as deposition Al plains at the mouth of a river or stream. A delta is formed where a stream or river deposits its sedimentary load into a standing body of water such as an ocean or lake. An alluvial fan is produced where a stream loses capacity by a greatly decreased gradient. A delta has subaerial and subaqueous components, but an alluvial fan is entirely subaerial. In terrestrial conditions, deltas and alluvial fans are reasonably distinct landforms. The juxtaposition of concomitant features composition and internal structure are sufficiently explicit as to avoid any confusion regarding their proper identification on Mars, the recognition of deltas and their distinction from alluvial fans is made difficult by low resolution imaging. Further, although it may be demonstrated that standing bodies of water existed on the surface of Mars, many of these bodies may have existed for extremely short periods of time (a few days to months); hence, distinctive shoreline features were not developed. Thus, in an attempt to derive a Martian classification of deltas, the inclusion of wholly subaerial deposits may be unavoidable. A simple, broad, morphological classification of Martian deltas, primarily on planimetric shape, includes digitate deltas, fan-shaped deltas, and re-entrant deltas. A fourth, somewhat problematical class includes featureless plains at the end of many valley systems.

The rivers of civilization

NASA Astrophysics Data System (ADS)

Macklin, Mark G.; Lewin, John

2015-04-01

The hydromorphic regimes that underpinned Old World river-based civilizations are reviewed in light of recent research. Notable Holocene climatic changes varied from region to region, whilst the dynamics of floodplain environments were equally diverse, with river channel changes significantly affecting human settlement. There were longer-term trends in Holocene hydroclimate and multi-centennial length 'flood-rich' and 'flood-poor' episodes. These impacted on five identified flooding and settlement scenarios: (i) alluvial fans and aprons; (ii) laterally mobile rivers; (iii) rivers with well-developed levees and flood basins; (iv) river systems characterised by avulsions and floodouts; and (v) large river-fed wetlands. This gave a range of changes that were either more or less regular or incremental from year-to-year (and thus potentially manageable) or catastrophic. The latter might be sudden during a flood event or a few seasons (acute), or over longer periods extending over many decades or even centuries (chronic). The geomorphic and environmental impacts of these events on riparian societies were very often irreversible. Contrasts are made between allogenic and autogenic mechanism for imposing environmental stress on riverine communities and a distinction is made between channel avulsion and contraction responses. Floods, droughts and river channel changes can precondition as well as trigger environmental crises and societal collapse. The Nile system currently offers the best set of independently dated Holocene fluvial and archaeological records, and the contrasted effects of changing hydromorphological regimes on floodwater farming are examined. The persistence of civilizations depended essentially on the societies that maintained them, but they were also understandably resilient in some environments (Pharaonic Egypt in the Egyptian Nile), appear to have had more limited windows of opportunity in others (the Kerma Kingdom in the Nubian Nile), or required

Suspended and Dissolved Matter in the Sacramento River and Delta Region Under Drought Conditions

NASA Astrophysics Data System (ADS)

Ackleson, S. G.; Rhea, W. J.; Blaser, S.; Wilkerson, F. P.; Dugdale, R. C.; Davis, C. O.; Tufillaro, N. B.

2016-02-01

The State of California is experiencing the fourth year of a historic drought that, as it continues to worsen, has raised concerns about future agricultural production and prompted emergency water restrictions. The Sacramento River drainage basin and estuary fall within the drought area classified as extreme to exceptional. To document the ecological effects of this drought and to serve as baseline conditions with which to compare future non-drought conditions, a series of seasonal field campaigns were conducted between June 2014 and October 2015 to characterize the concentration, composition, and morphology of particulate and dissolved matter within the lower reaches of the Sacramento River and delta region. In situ measurements of spectral light scatter and absorption due to water impurities are compared with water sample analyses for pigment and suspended sediment concentration. In situ measurements are used to derive remote sensing algorithms for impurity concentration and composition from above-water and remotely sensed radiometric measurements. Results indicate a seasonally stable riverine water mass and particle population feeding into a delta region with complicated hydrodynamics, point sources of wetland detritus and dissolved organic matter, and heterogeneous particle assemblages. Possible changes as a result of an El Nino are discussed.

LIS-HYMAP coupled Hydrological Modeling in the Nile River Basin and the Greater Horn of Africa

NASA Astrophysics Data System (ADS)

Jung, H. C.; Getirana, A.; Policelli, F. S.

2015-12-01

Water scarcity and resources in Africa have been exacerbated by periodic droughts and floods. However, few studies show the quantitative analysis of water balance or basin-scale hydrological modeling in Northeast Africa. The NASA Land Information System (LIS) is implemented to simulate land surface processes in the Nile River Basin and the Greater Horn of Africa. In this context, the Noah land surface model (LSM) and the Hydrological Modeling and Analysis Platform (HYMAP) are used to reproduce the water budget and surface water (rivers and floodplains) dynamics in that region. The Global Data Assimilation System (GDAS) meteorological dataset is used to force the system . Due to the unavailability of recent ground-based observations, satellite data are considered to evaluate first model outputs. Water levels at 10 Envisat virtual stations and water discharges at a gauging station are used to provide model performance coefficients (e.g. Nash-Sutcliffe, delay index, relative error). We also compare the spatial and temporal variations of flooded areas from the model with the Global Inundation Extent from Multi-Satellites (GIEMS) and the Alaska Satellite Facility (ASF)'s MEaSUREs Wetland data. Finally, we estimate surface water storage variations using a hypsographic curve approach with Shuttle Radar Topography Mission (SRTM) topographic data and evaluate the model-derived water storage changes in both river and floodplain. This study demonstrates the feasibility of using LIS-HYMAP coupled modeling to support seasonal forecast methods for prediction of decision-relevant metrics of hydrologic extremes.

Geohydrology of the Delta-Clearwater area, Alaska

USGS Publications Warehouse

Wilcox, Dorothy E.

1980-01-01

The alluvial aquifer in the Delta-Clearwater area, Alaska, is composed of lenticular, interbedded deposits of silt, sand, and gravel. Ground water occurs under both confined and unconfined conditions in the area. The potentiometric surface slopes approximately northward at gradients ranging from about 1 to 25 feet per mile. The aquifer is recharge by seepage through the streambeds of rivers and creeks and by infiltration of precipitation. Water is discharged from the aquifer into the Clearwater Creek network and Clearwater Lake, which are almost entirely spring-fed, at the mouth of the Delta River, and into the Tanana River along the northern boundary of the study area. Year-round ground-water discharge from the aquifer is estimated to exceed 1,200 cubic feet per second. The following ground-water flow system is hypothesized: Channel losses from the Gerstle River, several small creeks draining the Alaska Range, and the Tanana River to the east of Clearwater Creek recharge the sections of the aquifer discharging at the Clearwater Creek network. Channel losses from the Delta River and Jarvis Creek are the main source of recharge to the sections of the aquifer discharging in the vicinity of Clearwater Lake and Big Delta. Additional work is needed to verify these hypotheses. (USGS)

Evaluation of a floating fish guidance structure at a hydrodynamically complex river junction in the Sacramento-San Joaquin River Delta, California, USA

USGS Publications Warehouse

Romine, Jason G.; Perry, Russell W.; Pope, Adam C.; Stumpner, Paul; Liedtke, Theresa L.; Kumagai, Kevin K; Reeves, Ryan L

2016-01-01

Survival of out-migrating juvenile Chinook salmon (Oncorhynchus tshawytscha) in the Sacramento–San Joaquin River delta, California, USA, varies by migration route. Survival of salmonids that enter the interior and southern Delta can be as low as half that of salmonids that remain in the main-stem Sacramento River. Reducing entrainment into the higher-mortality routes, such as Georgiana Slough, should increase overall survival. In spring 2014, a floating fish-guidance structure (FFGS) designed to reduce entrainment into Georgiana Slough was deployed just upstream of the Georgiana Slough divergence. We used acoustic telemetry to evaluate the effect of the FFGS on Chinook entrainment to Georgiana Slough. At intermediate discharge (200–400 m3 s–1), entrainment into Georgiana Slough was five percentage points lower when the FFGS was in the on state (19.1% on; 23.9% off). At higher discharge (>400 m3 s–1), entrainment was higher when the FFGS was in the on state (19.3% on; 9.7% off), and at lower discharge (0–200 m3 s–1) entrainment was lower when the FFGS was in the on state (43.7% on; 47.3% off). We found that discharge, cross-stream fish position, time of day, and proportion of flow remaining in the Sacramento River contributed to the probability of being entrained to Georgiana Slough.

From the Mountains of the Moon to the Grand Renaissance: misinformation, disinformation and, finally, information for cooperation in the Nile River basin

NASA Astrophysics Data System (ADS)

Zaitchik, B. F.; Habib, S.; Anderson, M. C.; Ozdogan, M.

2012-12-01

The Nile River basin is shared by 11 nations and approximately 200 million people. Eight of the riparian States are defined as Least Developed Countries by the United Nations, and about 50% of the total basin population lives below the international poverty line. In addition, eight of the eleven countries have experienced internal or external wars in the past 20 years, six are predicted to be water scarce by 2025, and, at present, major water resource development projects are moving forward in the absence of a fully recognized basin-wide water sharing agreement. Nevertheless, the Nile basin presents remarkable opportunities for transboundary water cooperation, and today—notwithstanding significant substantive and perceived disagreements between stakeholders in the basin—this cooperation is beginning to be realized in topics ranging from flood early warning to hydropower optimization to regional food security. This presentation will provide an overview of historic and present challenges and opportunities for transboundary water management in the Nile basin and will present several case studies in which improved hydroclimatic information and communication systems are currently laying the groundwork for advanced cooperation. In this context climate change acts as both stress and motivator. On one hand, non-stationary hydrology is expected to tax water resources in the basin, and it undermines confidence in conventionally formulated water sharing agreements. On the other, non-stationarity is increasingly understood to be an exogenous threat to regional food and water security that will require informed, flexible cooperation between riparian states.

Natural and anthropogenic emissions of N and P to the Parnaíba River Delta in NE Brazil

NASA Astrophysics Data System (ADS)

de Paula Filho, Francisco José; Marins, Rozane Valente; de Lacerda, Luiz Drude

2015-12-01

The Parnaiba River Delta is the largest open sea delta in the Americas, having a unique ecological importance for the conservation of wildlife and fisheries resources. However, little is known about the biogeochemistry of this ecosystem. This study estimates N and P emissions to the delta using emissions factors, calibrated with field samples and N and P concentrations in different compartments of the delta. The estimated loads totaled 14.517 t N year-1 and 8.748 t P year-1, indicating that anthropogenic N and P emissions outweigh natural emissions by approximately 5 and 10 times, respectively. The activities that contribute the most to this result are livestock farming, agriculture and the release of untreated domestic sewage. The flows of N and P from the estimated loads corresponded to 339 kg N km-2 year-1 and 204 kg P km-2 year-1, so the region can be classified as "meso-active" and "eury-active" with regard to the transfer of nutrients. These results are consistent with the coastal megabasin design (COSCATs) proposed by Meyback et al. (2006). This article presents a first approach to the calculation of an estimated annual emissions inventory of N and P for the lower basin of the Parnaíba River and its coastal region, representing an approach that has been satisfactorily used in assessing the sensitivity of estuarine systems in northeastern Brazil.

MODELING THE IMPACTS OF DECADAL CHANGES IN RIVERINE NUTRIENT FLUXES ON COASTAL EUTROPHICATION NEAR THE MISSISSIPPI RIVER DELTA. (R827785E02)

EPA Science Inventory

A mathematical model was used to link decadal changes in the Mississippi River nutrient flux to coastal eutrophication near the Mississippi River Delta. Model simulations suggest that bottom water hypoxia intensified about 30 years ago, as a probable consequence of increased n...

The impact of Cyclone Nargis on the Ayeyarwady (Irrawaddy) River delta shoreline and nearshore zone (Myanmar): Towards degraded delta resilience?

NASA Astrophysics Data System (ADS)

Besset, Manon; Anthony, Edward J.; Dussouillez, Philippe; Goichot, Marc

2017-10-01

The Ayeyarwady River delta (Myanmar) is exposed to tropical cyclones, of which the most devastating has been cyclone Nargis (2-4 May 2008). We analysed waves, flooded area, nearshore suspended sediments, and shoreline change from satellite images. Suspended sediment concentrations up to 40% above average during the cyclone may reflect fluvial mud supply following heavy rainfall and wave reworking of shoreface mud. Massive recession of the high-water line resulted from backshore flooding by cyclone surge. The shoreline showed a mean retreat of 47 m following Nargis. Erosion was stronger afterwards (-148 m between August 2008 and April 2010), largely exceeding rates prior to Nargis (2000-2005: -2.14 m/year) and over 41 years (1974-2015: -0.62 m/year). This implies that resilience was weak following cyclone impact. Consequently, the increasingly more populous Ayeyarwady delta, rendered more and more vulnerable by decreasing fluvial sediment supply, could, potentially, become more severely impacted by future high-energy events.

Spawning and movement behavior of migratory coastal cutthroat trout on the western Copper River delta, Alaska.

Treesearch

D.A. Saiget; M.R. Sloat; Reeves. G.H.

2007-01-01

We studied the movement patterns of migratory coastal cutthroat trout Oncorhynchus clarkii clarkii in the western Copper River delta, Alaska, near the northern extent of the subspecies' distribution. Life history information for coastal cutthroat trout is scarce within this region. Movement of coastal cutthroat trout was monitored from 1994 to...

Plan form changes of Gumara River channel over 50 years (Upper Blue Nile basin, Ethiopia)

NASA Astrophysics Data System (ADS)

Abate, Mengiste; Nyssen, Jan; Mehari, Michael

2014-05-01

Channel plan form changes were investigated along the 65 km long Gumara River in Lake Tana basin (Ethiopia) by overlaying information from aerial photographs and SPOT imagery. Two sets of aerial photographs (1957 and 1980) were scanned, and then orthorectified in ENVI 4.2 environment. Recent channel plan form information was extracted from SPOT images of 2006. ERDAS 2010 and ArcGIS 10.1 tools were used for the data preparation and analysis. The information on river plan form changes spans from 1957 to 2006 (49 years), during which time the Gumara catchment has been subjected to changes in land use/cover and increasing water abstraction, which may have affected its hydrogeomorphology. The results indicated that the lower reach of Gumara at its mouth has undergone major plan form changes. A delta of 1.12 km² was created between 1957 and 1980 and additional 1.00 km² land has been created between 1980 and 2006. The sinuosity of the plan form changed only slightly through the study period: 1.78 in 1957, 1.76 in 1980, and 1.81 in 2006. Comparison of cross sections at the hydrological gauging station showed that the river bed aggraded in the order of 1.5 m to 2.5 m for the period 1963-2009. The trend analysis of stream flow of Gumara River versus rainfall in the catchment also indicated that the bed level of the Gumara river at its gauging station has risen. From field observations, the impact of direct human interventions was identified. The building of artificial levees along the river banks has contributed to huge deposition in the river bed. At locations where intensive irrigation takes place in the floodplain, seepage water through the banks created river bank failure and modifications in plan form. The unstable segments of the river reach were identified and will be further analysed.

West Nile virus: Uganda, 1937, to New York City, 1999.

PubMed

Hayes, C G

2001-12-01

West Nile virus, first isolated in 1937, is among the earliest arthropod-borne viruses discovered by humans. Its broad geographical distribution, not uncommon infection of humans, transmission by mosquitoes, and association with wild birds as enzootic hosts were well documented by the mid-1960s. However, West Nile virus was not considered to be a significant human pathogen because most infections appeared to result in asymptomatic or only mild febrile disease. Several epidemics had been documented prior to 1996, some involving hundreds to thousands of cases in mostly rural populations, but only a few cases of severe neurological disease had been reported. The occurrence between 1996 and 1999 of three major epidemics, in southern Romania, the Volga delta in southern Russia, and the northeastern United States, involving hundreds of cases of severe neurological disease and fatal infections was totally unexpected. These were the first epidemics reported in large urban populations. A significant factor that appeared in common to all three outbreaks was the apparent involvement of the common house mosquito, Culex pipiens, as a vector. This species had not previously been implicated as important in the transmission of West Nile virus. In addition the epidemic in the northeastern United States was unusual in the association of West Nile virus infection with fatal disease of birds, suggesting a change in the virulence of the virus toward this host. Understanding the risk factors that contributed to these three urban epidemics is important for minimizing the potential for future occurrences. This review will attempt to compare observations on the biology of West Nile virus made over about 60 years prior to the recent epidemics to observations made in association with these urban epidemics.

Examining the Impact of Nitrous Acid Chemistry on Ozone and PM over the Pearl River Delta Region

EPA Science Inventory

The impact of nitrous acid (HONO) chemistry on regional ozone and particulate matter in Pearl River Delta region was investigated using the community multiscale air quality (CMAQ) modeling system and the CB05 mechanism. Model simulations were conducted for a ten-day period in Oct...

Holocene alluvial history and archaeological significance of the Nile floodplain in the Saqqara-Memphis region, Egypt

NASA Astrophysics Data System (ADS)

Hassan, F. A.; Hamdan, M. A.; Flower, R. J.; Shallaly, N. A.; Ebrahem, E.

2017-11-01

A suite of drill cores undertaken on the Saqqara-Memphisfloodplain revealed an array of Late Pleistocene-Holocene sediment facies that show a complex of spatio-temporal changes in sediment related to migration of the River Nile, Nile flood variations, settlement sites and climate change. The recovered data enhance our understanding of the history of the modern River Nile and its relationship to the emergence and continuity of Egyptian civilization. The floodplain of the Saqqara-Memphis area reveals a sequence of aggradation and degradation events comprising six clearly marked sedimentary units (I-VI), overlying Late Pleistocene fluvial sand and gravel (unit I). Deposition of unit II resumed during a period of high Nile flow, rapid sea level rise and locally wet climatic conditions. As a result, the floodplain was occupied by swamps and anastomosing channels. Subsequently, the Nile changed to a more stable meandering channel system with well-developed levees and flood basins (unit III). This aggradation unit was subsequently eroded by the end of Old Kingdom (ca. 4.2 kyr cal BP). The degradation hiatus was followed by a widespread layer of alluvial silt and sand indicating very high Nile floods that coincide with historical records of very high floods during the Middle Kingdom and frequently high floods during the New Kingdom (unit IV). During the last two thousand years (units VI-VII) floods generally diminished except for several notable lows and highs. Our calculations of the long-term rate of siltation during the Middle and Late Holocene suggest an average rate of 0.235 m/century rather than the commonly cited 0.09-0.12 m per century. In addition, our study of satellite imagery of the Memphite region in the context of archaeological data combined with our own geological studies reveal that the main Nile in Neolithic and Predynastic times (ca.7.0-5.0 kyr cal BP) ran along the eastern edge of the current floodplain. A lateral branch of the Nile ran along the

[Distribution characteristics of soil organic carbon and its composition in Suaeda salsa wetland in the Yellow River delta].

PubMed

Dong, Hong-Fang; Yu, Jun-Bao; Guan, Bo

2013-01-01

Applying the method of physical fractionation, distribution characteristics of soil organic carbon and its composition in Suaeda salsa wetland in the Yellow River delta were studied. The results showed that the heavy fraction organic carbon was the dominant component of soil organic carbon in the studied region. There was a significantly positive relationship between the content of heavy fraction organic carbon, particulate organic carbon and total soil organic carbon. The ranges of soil light fraction organic carbon ratio and content were 0.008% - 0.15% and 0.10-0.40 g x kg(-1), respectively, and the range of particulate organic carbon ratio was 8.83% - 30.58%, indicating that the non-protection component of soil organic carbon was low and the carbon pool was relatively stable in Suaeda salsa wetland of the Yellow River delta.

Distribution and abundance of the Yuma clapper rail (Rallus longirostris yumanensis) in the Colorado River delta, México

USGS Publications Warehouse

Hinojosa-Huerta, Osvel; DeStefano, Stephen; Shaw, William W.

2001-01-01

We estimated the abundance of Yuma clapper rails in the Ciénega de Santa Clara and determined the distribution of the subspecies in the Colorado River delta region in México. The maximum estimate of abundance was 6629 individuals (95% C.I. 4859–8399), assuming a response rate by rails to taped calls of 60%. Rails were widely distributed in the delta, occupying almost all marshlands dominated by cattail. As this is an endangered subspecies shared by México and the U.S., the conservation of the delta ecosystem should be the interest of both countries, especially when water management decisions upstream in the U.S. have an impact over natural areas downstream in México.

The Nile floodplain, hydroclimatic variability, and its relation with cultural dynamics in ancient Thebes (Luxor, Egypt)

NASA Astrophysics Data System (ADS)

Toonen, Willem H. J.; Graham, Angus; Pennington, Ben; Hunter, Morag; Strutt, Kris; Barker, Dominic; Masson, Aurelia; Emery, Virginia

2016-04-01

The western bank of the river Nile in the Luxor region (Egypt) separates New Kingdom divine temple complexes in the central axis of the river valley from contemporaneous sites on the desert edge and limestone plateau. The intermediate Nile floodplain features relatively few known archaeological sites, but played an important role in the ancient ritual landscape by connecting the focal region of the living (floodplain) with that of the dead (desert). All Royal Funerary Temple Complexes of the New Kingdom period (1539-1077 BCE), which played a central role in the cosmogonical landscape, are positioned within a confined 3.5 km long strip of land on the western edge of the present floodplain. This preferential location, together with contemporary textual sources and tomb scenes suggesting the nearby presence of canals, have led to the hypothesis that natural and human-made waterways may have once connected the main channel of the Nile with the desert edge. Until the present research took place, no detailed study of pre-existing channel networks existed in the region, leaving a gap in current knowledge on the configuration and use of the ancient floodplain. This study presents the results of a multi-disciplinary study aimed at mapping and dating ancient waterways in the Theban region and aims to find evidence for the natural or human origin of such channels. Boreholes and Electric Resistivity Tomography (ERT) were carried out along a transect that connects the edge of the Holocene floodplain with the current position of the river Nile. Satellite imagery and textual sources were also used to augment the fieldwork. The data indicate the presence of an infilled abandoned channel of the Nile in the western distal part of the current floodplain, adjoining the Funerary Temple complexes. Over 2100 ceramic fragments were analysed from the sedimentary infilling of the silted-up river course, dating it to the end of the New Kingdom, and indicating that the channel and temples

Innovation in monitoring: The U.S. Geological Survey Sacramento–San Joaquin River Delta, California, flow-station network

USGS Publications Warehouse

Burau, Jon; Ruhl, Cathy; Work, Paul A.

2016-01-29

The U.S. Geological Survey (USGS) installed the first gage to measure the flow of water into California’s Sacramento–San Joaquin River Delta from the Sacramento River in the late 1800s. Today, a network of 35 hydro-acoustic meters measure flow throughout the delta. This region is a critical part of California’s freshwater supply and conveyance system. With the data provided by this flow-station network—sampled every 15 minutes and updated to the web every hour—state and federal water managers make daily decisions about how much freshwater can be pumped for human use, at which locations, and when. Fish and wildlife scientists, working with water managers, also use this information to protect fish species affected by pumping and loss of habitat. The data are also used to help determine the success or failure of efforts to restore ecosystem processes in what has been called the “most managed and highly altered” watershed in the country.

The modern Nile sediment system: Processes and products

NASA Astrophysics Data System (ADS)

Garzanti, Eduardo; Andò, Sergio; Padoan, Marta; Vezzoli, Giovanni; El Kammar, Ahmed

2015-12-01

We trace compositional changes of Nile sediments for 7400 km, from their sources in equatorial rift highlands of Burundi and Rwanda to their sink in the Mediterranean Sea. All chemical and physical controls on sediment petrography, mineralogy and geochemistry, including weathering, grain-size, hydraulic sorting, mechanical breakdown, anthropic impact, mixing and recycling are investigated in detail. The Nile course is controlled along its entire length by the East African-Red Sea Rift. In this anorogenic setting, detritus is derived in various proportions from volcanic fields associated with tectonic extension (Anorogenic Volcanic provenance) and from igneous, metamorphic and sedimentary rocks uplifted on the rift shoulders or exposed on the craton (Continental Block provenance). The entire spectrum of such detrital signatures is displayed in the Nile catchment. Volcaniclastic Atbara sand is generated by focused erosion of the Ethiopian basaltic plateau in semiarid climate, whereas quartzose White Nile sand reflects low erosion rates, extensive weathering and sediment trapping in lakes and swamps at equatorial to subequatorial latitudes. In the main Nile, as in its main tributary the Blue Nile, suspended load is volcaniclastic, whereas feldspatho-quartzose bedload is derived largely from basement sources, with fine to medium-grained eolian sand added along the lower course. Mixing of detrital populations with different provenance and grain size is reflected in diverse violations of settling-equivalence relationships in fluvial and deltaic sediments. Sediment delivery from Sudan has been cut off after closure of the Aswan High Dam and accelerated erosion of deltaic cusps is leading to local formation of placer lags dominated by ultradense Fe-Ti-Cr oxides, but mineralogical changes caused by man's radical modification of fluvial regimes have been minor so far. In beaches of Sinai, Gaza and Israel, the Nile volcaniclastic trace gets progressively diluted by quartzose

[Secondary metabolites of halotolerant fungus Penicillium chrysogenum HK14-01 from the Yellow River Delta area].

PubMed

Qu, Peng; Liu, Peipei; Fu, Peng; Wang, Yi; Zhu, Weiming

2012-09-04

To search for structurally novel and biologically active compounds from the secondary metabolites of halotolerant fungi from the Yellow River Delta area. We screened halotolerant fungi with rich chemical diversity and antitumor or antimicrobial activity by means of integrated chemical and biological method. We cultured halotolerant fungi under different conditions at first. Then we investigated the chemical diversity and the bioactivity of the EtOAc extracts of the fermentation broth by HPLC and TLC, and cytotoxic assay or antimicrobial assay. We selected Penicillium chrysogenum HK14-01 to further study for the large yield, producing alkaloids and cytotoxicity on P388 cells in YMDP culture medium containing 10% NaCl. We fermented P. chrysogenum HK14-01 on a large scale; we isolated and purified the compounds by column chromatography over silica gel, Sephadex LH-20, and semipreparative HPLC; and we identified the structures by spectroscopic analysis, X-ray diffraction (Mo-Kalpha), CD spectra and the time-dependent density functional theory electronic circular dichroism (TDDFT ECD) calculation. We isolated and identified a halotolerant fungal strain, P. chrysogenum HK14-01, from the sediments collected in the Yellow River Delta area. From the fermentation broth of P. chrysogenum HK14-01, we isolated and identified eight compounds, i.e. (2S,3R)-oxaline (1, a major product), (3R, 4R)-3,4,8-trihydroxy-3,4-dihydronaphthalen-1 (2H)-one (2), (Z)-N-(4-hydroxy styryl) formamide (3), (E)-N-(4-hydroxystyryl) formamide (4), emodin (5), 4-(2-hydroxyethyl) benzene-1,2-diol (6), methyl 2-(4-hydroxyphenyl) acetate (7), and 2-(4-hydroxyphenyl) acetonitrile (8). Bioactive compounds can be obtained from the secondary metabolites of halotolerant microorganisms from the Yellow River Delta area.

Assessing the contribution of wetlands and subsided islands to dissolved organic matter and disinfection byproduct precursors in the Sacramento-San Joaquin River Delta: A geochemical approach

USGS Publications Warehouse

Kraus, T.E.C.; Bergamaschi, B.A.; Hernes, P.J.; Spencer, R.G.M.; Stepanauskas, R.; Kendall, C.; Losee, R.F.; Fujii, R.

2008-01-01

This study assesses how rivers, wetlands, island drains and open water habitats within the Sacramento-San Joaquin River Delta affect dissolved organic matter (DOM) content and composition, and disinfection byproduct (DBP) formation. Eleven sites representative of these habitats were sampled on six dates to encompass seasonal variability. Using a suite of qualitative analyses, including specific DBP formation potential, absorbance, fluorescence, lignin content and composition, C and N stable isotopic compositions, and structural groupings determined using CPMAS (cross polarization, magic angle spinning) 13C NMR, we applied a geochemical fingerprinting approach to characterize the DOM from different Delta habitats, and infer DOM and DBP precursor sources and estimate the relative contribution from different sources. Although river input was the predominant source of dissolved organic carbon (DOC), we observed that 13-49% of the DOC exported from the Delta originated from sources within the Delta, depending on season. Interaction with shallow wetlands and subsided islands significantly increased DOC and DBP precursor concentrations and affected DOM composition, while deep open water habitats had little discernable effect. Shallow wetlands contributed the greatest amounts of DOM and DBP precursors in the spring and summer, in contrast to island drains which appeared to be an important source during winter months. The DOM derived from wetlands and island drains had greater haloacetic acid precursor content relative to incoming river water, while two wetlands contributed DOM with greater propensity to form trihalomethanes. These results are pertinent to restoration of the Delta. Large scale introduction of shallow wetlands, a proposed restoration strategy, could alter existing DOC and DBP precursor concentrations, depending on their hydrologic connection to Delta channels. ?? 2008 Elsevier Ltd.

Geomorphological and geotechnical issues affecting the seismic slope stability of the Duwamish River Delta, Port of Seattle, Washington

USGS Publications Warehouse

Kayen, Robert E.; Barnhardt, Walter A.; Palmer, Stephen P.

1999-01-01

Young Holocene deposits of the Duwamish River valley underlie a highly developed transportation-industrial corridor, extending from the City of Kent to the Elliott Bay-Harbor Island marine terminal facilities. The deposits have been shaped by relative sea-level rise, but also by episodic volcanism and seismicity. A geologic and geotechnical investigation of these river-mouth deposits indicates high initial liquefaction susceptibility during earthquakes, and possibly the potential for unlimited-strain disintegrative flow failure of the delta front.

Prediction of future climate change for the Blue Nile, using RCM nested in GCM

NASA Astrophysics Data System (ADS)

Sayed, E.; Jeuland, M.; Aty, M.

2009-04-01

Although the Nile River Basin is rich in natural resources, it faces many challenges. Rainfall is highly variable across the region, on both seasonal and inter-annual scales. This variability makes the region vulnerable to droughts and floods. Many development projects involving Nile waters are currently underway, or being studied. These projects will lead to land-use patterns changes and water distribution and availability. It is thus important to assess the effects of a) these projects and b) evolving water resource management and policies, on regional hydrological processes. This paper seeks to establish a basis for evaluation of such impacts within the Blue Nile River sub-basin, using the RegCM3 Regional Climate Model to simulate interactions between the land surface and climatic processes. We first present results from application of this RCM model nested with downscaled outputs obtained from the ECHAM5/MPI-OM1 transient simulations for the 20th Century. We then investigate changes associated with mid-21st century emissions forcing of the SRES A1B scenario. The results obtained from the climate model are then fed as inputs to the Nile Forecast System (NFS), a hydrologic distributed rainfall runoff model of the Nile Basin, The interaction between climatic and hydrological processes on the land surface has been fully coupled. Rainfall patterns and evaporation rates have been generated using RegCM3, and the resulting runoff and Blue Nile streamflow patterns have been simulated using the NFS. This paper compares the results obtained from the RegCM3 climate model with observational datasets for precipitation and temperature from the Climate Research Unit (UK) and the NASA Goddard Space Flight Center GPCP (USA) for 1985-2000. The validity of the streamflow predictions from the NFS is assessed using historical gauge records. Finally, we present results from modeling of the A1B emissions scenario of the IPCC for the years 2034-2055. Our results indicate that future

Changing Course - the Baird Team Solution: a Delta for All

NASA Astrophysics Data System (ADS)

Nairn, R. B.

2016-02-01

The Changing Course Design competition was initiated to evaluate options for re-positioning the mouth of the Mississippi River and modifying the management of the Lower Mississippi River to support the 2017 Master Plan for the Louisiana coast. This paper will present the findings of one of the selected competitors: the Baird Team and their "Delta for All" approach. A key to success in the future management of the lower Mississippi River is the development of an integrated, holistic approach to management that recognizes the need to harness the full land/wetland building and restorative potential of the river at the same time as improving flood protection and navigation. Fundamentally the Baird solution recognized the underlying geomorphic challenges of the Delta: it receives three to four times less sediment from the Mississippi River than it did historically and sea level is rising two to three times faster than it did historically and is predicted to rise much faster in the future. The result will be a smaller delta in the future. Our approach seeks to harness as close to 100% of the land building potential of the river to make the smaller future delta as large as possible. This compares to the 2012 State Master Plan which would harness approximately 50% of the land-building potential. Our approach also recognizes that the further inland new distributary mouths and associated sub-deltas are located, the greater the delta building potential. Our approach builds with the river by creating and managing new river distributaries that are opened and closed every 50 years or so to build new sub-deltas within a defined sustainable delta footprint. By placing the last outlet somewhere in the vicinity of English Turn the lower Mississippi River would become a tidal channel. These two simple concepts of harnessing 100% of the river and placing the last outlet near English Turn result in immediate and significant benefits for flood protection and navigation. Through the

Spatial distribution and partition of perfluoroalkyl acids (PFAAs) in rivers of the Pearl River Delta, southern China.

PubMed

Liu, Baolin; Zhang, Hong; Xie, Liuwei; Li, Juying; Wang, Xinxuan; Zhao, Liang; Wang, Yanping; Yang, Bo

2015-08-15

This study investigated the occurrence of perfluoroalkyl acids (PFAAs) in surface water from 67 sampling sites along rivers of the Pearl River Delta in southern China. Sixteen PFAAs, including perfluoroalkyl carboxylic acids (PFCAs, C5-14, C16 and C18) and perfluoroalkyl sulfonic acids (PFSAs, C4, C6, C8 and C10) were determined by high performance liquid chromatography-negative electrospray ionization-tandem mass spectrometry (HPLC/ESI-MS/MS). Total PFAA concentrations (∑ PFAAs) in the surface water ranged from 1.53 to 33.5 ng·L(-1) with an average of 7.58 ng·L(-1). Perfluorobutane sulfonic acid (PFBS), perfluorooctanoic acid (PFOA), and perfluorooctane sulfonic acid (PFOS) were the three most abundant PFAAs and on average accounted for 28%, 16% and 10% of ∑ PFAAs, respectively. Higher concentrations of ∑ PFAAs were found in the samples collected from Jiangmen section of Xijiang River, Dongguan section of Dongjiang River and the Pearl River flowing the cities which had very well-developed manufacturing industries. PCA model was employed to quantitatively calculate the contributions of extracted sources. Factor 1 (72.48% of the total variance) had high loading for perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), PFBS and PFOS. For factor 2 (10.93% of the total variance), perfluorononanoic acid (PFNA) and perfluoroundecanoic acid (PFUdA) got high loading. The sorption of PFCAs on suspended particulate matter (SPM) increased by approximately 0.1 log units for each additional CF2 moiety and that on sediment was approximately 0.8 log units lower than the SPM logKd values. In addition, the differences in the partition coefficients were influenced by the structure discrepancy of absorbents and influx of fresh river water. These data are essential for modeling the transport and environmental fate of PFAAs. Copyright © 2015 Elsevier B.V. All rights reserved.

West Nile virus circulation in South-Eastern Romania, 2011 to 2013.

PubMed

Dinu, S; Cotar, A I; Pănculescu-Gătej, I R; Fălcuţă, E; Prioteasa, F L; Sîrbu, A; Oprişan, G; Bădescu, D; Reiter, P; Ceianu, C S

2015-05-21

Lineage 2 West Nile virus (WNV), previously found only in sub-Saharan Africa and Madagascar, was identified in Hungary in 2004 and has rapidly expanded in Europe in the past decade. Following a significant outbreak of West Nile fever with neurological cases caused by lineage 1 WNV in Romania in 1996, scattered cases have been recorded in the south-east of the country in each transmission season. Another outbreak, affecting a larger area and caused by lineage 2 WNV, was recorded in 2010. We analysed human sera from neuroinvasive West Nile fever cases and mosquitoes, sampled in south-eastern Romania between 2011 and 2013, for the presence of WNV genome, and obtained partial NS5 and envelope glycoprotein sequences. Human- and mosquito-derived WNV sequences were highly similar (99%) to Volgograd 2007 lineage 2 WNV and differed from isolates previously detected in central and southern Europe. WNV was detected in one pool of Culex pipiens s.l. males, documenting vertical transmission. Lineage 4 WNV, of unknown pathogenicity to mammals, was found in the amphibian-feeding mosquito Uranotaenia unguiculata from the Danube Delta. Our results present molecular evidence for the maintenance of the same isolates of Volgograd 2007-like lineage 2 WNV in south-eastern Romania between 2011 and 2013.

Salt geometry influence on present-day stress orientations in the Nile Delta: Insights from numerical modeling

NASA Astrophysics Data System (ADS)

Eckert, Andreas; Zhang, Weicheng

2016-02-01

The offshore Nile Delta displays sharply contrasting orientations of the maximum horizontal stress, SH, in regions above Messinian evaporites (suprasalt) and regions below Messinian evaporites (subsalt). Published stress orientation data predominantly show margin-normal suprasalt SH orientations but a margin-parallel subsalt SH orientation. While these data sets provide the first major evidence that evaporite sequences can act as mechanical detachment horizons, the cause for the stress orientation contrast remains unclear. In this study, 3D finite element analysis is used to investigate the causes for stress re-orientation based on two different hypotheses. The modeling study evaluates the influence of different likely salt geometries and whether stress reorientations are the result of basal drag forces induced by gravitational gliding or whether they represent localized variations due to mechanical property contrasts. The modeling results show that when salt is present as a continuous layer, gravitational gliding occurs and basal drag forces induced in the suprasalt layers result in the margin-normal principal stress becoming the maximum horizontal stress. With the margin-normal stress increase being confined to the suprasalt layers, the salt acts as a mechanical detachment horizon, resulting in different SH orientations in the suprasalt compared to the subsalt layers. When salt is present as isolated bodies localized stress variations occur due to the mechanical property contrasts imposed by the salt, also resulting in different SH orientations in the suprasalt compared to the subsalt layers. The modeling results provide additional quantitative evidence to confirm the role of evaporite sequences as mechanical detachment horizons.

Measuring Bedload Sediment Flux in Large Rivers: New Data from the Mekong River and Its Applications in Assessing Geomorphic Change

NASA Astrophysics Data System (ADS)

Best, J.; Hackney, C. R.; Parsons, D. R.; Darby, S. E.; Leyland, J.; Aalto, R. E.; Nicholas, A. P.

2014-12-01

Many large rivers are undergoing renewed and increasing anthropogenic-induced change as water diversions, new dams and greater water demands place enhanced stresses on these river basins. Examples of rivers undergoing significant change include the Amazon, Madeira, Nile, Yangtze and Mekong, with considerable ongoing debate raging as to the long-term geomorphic and ecological effects of major anthropogenic interventions. Assessing the effects of such change in large rivers is demanding, one reason being that sediment transport is often exceedingly difficult to measure, and thus data needed to inform the debate on the impact of anthropogenic change is frequently lacking. Here, we report on one aspect of research being undertaken as part of STELAR-S2S - Sediment Transfer and Erosion on Large Alluvial Rivers - that is seeking to better understand the relationship between climate, anthropogenic impacts and sediment transport in some of the world's largest rivers. We are using the Lower Mekong River as our study site, with the Mekong delta being one of only three in the world classified by the IPCC as 'extremely vulnerable' to future changes in climate. Herein, we describe details of bedload sediment flux estimation using repeated high-resolution multibeam echo sounder (MBES) bathymetric mapping along the Lower Mekong and Tonle Sap rivers in Cambodia. We are using MBES to quantify the spatial variation in sediment transport both along and also across the river at 11 sites in the study area. Predicted increases in the extraction of sediment from the river through sand dredging are thought likely to cause a significant decrease in downstream sediment flux, and future dam construction along the Mekong main channel potentially offers another source of significant change. These field results will be set in the light of these anthropogenic drivers on sediment flux in the Mekong River and their possible future effects on bar formation and channel migration.

Changing Course: The Studio Misi-Ziibi Team_ New Misi-Ziibi Living Delta

NASA Astrophysics Data System (ADS)

Hoal, J.

2016-02-01

Acknowledging that the Mississippi River Delta will continue to evolve over the next 100 years, the new MISI-ZIIBI LIVING DELTA for the 22nd century - a healthy, productive and resilient delta - relies on a synergistic and leveraged combination of delta building, the working delta, and delta living. This new Delta will be more sustainable and smaller in area, but have faster vertical accretion rates than earlier deltas, which keeps pace with current and future rates of global sea-level rise. The vision for the new Delta will be achieved through ECO 3D [dredge + dump, dredge-siphon, divert] - in which the bounded Mississippi River will be fragmented into a network of constructed distributaries, using sediment diversions, in order to feed the wetlands with the necessary sediment for delta building. Although the diversions will be constructed and managed, the delta formation in the receiving basins is self-organizing and naturally formed. In addition, we propose to shorten the Mississippi River and construct a new navigation entry point further upstream with a new distributary node near West Point à la Hache. The realigned and shortened river provides more efficient methods to use the sediment loads and increase safety and navigation reliability, and lower flood levels along the Mississippi River in this area. Ensuring that the navigation and marine economy continues to expand the river will be dredged to 50ft deep, the existing ports and Port Fourchon expanded, existing navigable inland water bodies maintained, and a new port constructed in the new Bird's Foot. We propose retreat from the southern rim of the existing Delta in order to assure long-term sustainability of the regions with the highest population density and economic productivity. The concept of DELTA LIVING is about embracing the ideology and cultural aspect of communities by enabling a means to continue to live with the Delta in new ways, and accommodating a regional growth strategy of safe, strong

Regional view of a Trans-African Drainage System.

PubMed

Abdelkareem, Mohamed; El-Baz, Farouk

2015-05-01

Despite the arid to hyperarid climate of the Great Sahara of North Africa, pluvial climates dominated the region. Radar data shed some light on the postulated Trans-African Drainage System and its relationship to active and inactive tributaries of the Nile basin. Interpretations of recent elevation data confirm a source of the river water from the Red Sea highlands did not connect the Atlantic Ocean across Tushka basin, highlands of Uwinate and Darfur, and Chad basin, but northward to the ancestral Nile Delta. Elements of topography and climate were considered. They show that the former segments of the Nile closely mirror present-day tributaries of the Nile basin in drainage geometry, landscape, and climate. A rainfall data interpolation scenario revealed that this basin received concurrent runoff from both flanks such as Gabgaba-Allaqi to the east and Tushka basin to the west, similar to present-day Sobat and White Nile tributaries, respectively. Overall the western tributaries such as those of Tushka basin and Howar lead to the Nile, which was (and still is) the biggest river system in Africa.

Regional view of a Trans-African Drainage System

PubMed Central

Abdelkareem, Mohamed; El-Baz, Farouk

2014-01-01

Despite the arid to hyperarid climate of the Great Sahara of North Africa, pluvial climates dominated the region. Radar data shed some light on the postulated Trans-African Drainage System and its relationship to active and inactive tributaries of the Nile basin. Interpretations of recent elevation data confirm a source of the river water from the Red Sea highlands did not connect the Atlantic Ocean across Tushka basin, highlands of Uwinate and Darfur, and Chad basin, but northward to the ancestral Nile Delta. Elements of topography and climate were considered. They show that the former segments of the Nile closely mirror present-day tributaries of the Nile basin in drainage geometry, landscape, and climate. A rainfall data interpolation scenario revealed that this basin received concurrent runoff from both flanks such as Gabgaba-Allaqi to the east and Tushka basin to the west, similar to present-day Sobat and White Nile tributaries, respectively. Overall the western tributaries such as those of Tushka basin and Howar lead to the Nile, which was (and still is) the biggest river system in Africa. PMID:26257941

Sediment-hosted contaminants and distribution patterns in the Mississippi and Atchafalaya River Deltas

USGS Publications Warehouse

Flocks, James G.; Kindinger, Jack G.; Ferina, Nicholas; Dreher, Chandra

2002-01-01

The Mississippi and Atchafalaya Rivers transport very large amounts of bedload and suspended sediments to the deltaic and coastal environments of the northern Gulf of Mexico. Absorbed onto these sediments are contaminants that may be detrimental to the environment. To adequately assess the impact of these contaminants it is first necessary to develop an understanding of sediment distribution patterns in these deltaic systems. The distribution patterns are defined by deltaic progradational cycles. Once these patterns are identified, the natural and industrial contaminant inventories and their depositional histories can be reconstructed. Delta progradation is a function of sediment discharge, as well as channel and receiving-basin dimensions. Fluvial energy controls the sediment distribution pattern, resulting in a coarse grained or sandy framework, infilled with finer grained material occupying the overbank, interdistributary bays, wetlands and abandoned channels. It has been shown that these fine-grained sediments can carry contaminants through absorption and intern them in the sediment column or redistribute them depending on progradation or degradation of the delta deposit. Sediment distribution patterns in delta complexes can be determined through high-resolution geophysical surveys and groundtruthed with direct sampling. In the Atchafalaya and Mississippi deltas, remote sensing using High-Resolution Single-Channel Seismic Profiling (HRSP) and Sidescan Sonar was correlated to 20-ft vibracores to develop a near-surface geologic framework that identifies variability in recent sediment distribution patterns. The surveys identified bedload sand waves, abandoned-channel back-fill, prodelta and distributary mouth bars within the most recently active portions of the deltas. These depositional features respond to changes in deltaic processes and through their response may intern or transport absorbed contaminants. Characterizing these features provides insight into the

Altamaha River Delta, Georgia Sea Islands

NASA Technical Reports Server (NTRS)

2001-01-01

The history of sea islands in the Altamaha River delta on the coast of Georgia is revealed in this image produced from data acquired by the Airborne Synthetic Aperture Radar (AIRSAR), developed and operated by NASA's Jet Propulsion Laboratory, Pasadena, Calif. The outlines of long-lost plantation rice fields, canals, dikes and other inlets are clearly defined. Salt marshes are shown in red, while dense cypress and live oak tree canopies are seen in yellow-greens.

Agricultural development of the Altamaha delta began soon after the founding of the Georgia Colony in 1733. About 25 plantations were located on the low-lying islands and shores by the 19th century, taking advantage of the rich alluvial flow and annual inundation of water required by some crops. The first major crop was indigo; when demand for that faded, rice and cotton took its place. A major storm in 1824 destroyed much of the town of Darien (upper right) and put many of the islands under 20 feet of water. The Civil War ended the plantation system, and many of the island plantations disappeared under heavy brush and new growth pine forests. Some were used as tree farms for paper and pulp industries, while the Butler Island (center left) plantation became a wildlife conservation site growing wild sea rice for migrating ducks and other waterfowl. Margaret Mitchell is reputed to have used the former owner of the Butler Plantation as a basis for the Rhett Butler character in her novel 'Gone With The Wind,' taking the first name from Rhett's Island (lower right).

These data were obtained during a 1994-95 campaign along the Georgia coast. AIRSAR's ability to detect vegetation canopy density, hydrological features and other topographic characteristics is a useful tool in landscape archaeology. AIRSAR flies aboard a NASA DC-8 based at NASA's Dryden Flight Research Center, Edwards, Calif. The analysis on the data shown was accomplished by Dr. Gary Mckay, Department of Archaeology and Geography, and Ian

Permafrost Organic Carbon Mobilization From the Watershed to the Colville River Delta: Evidence From 14C Ramped Pyrolysis and Lignin Biomarkers

NASA Astrophysics Data System (ADS)

Zhang, Xiaowen; Bianchi, Thomas S.; Cui, Xingqian; Rosenheim, Brad E.; Ping, Chien-Lu; Hanna, Andrea J. M.; Kanevskiy, Mikhail; Schreiner, Kathryn M.; Allison, Mead A.

2017-11-01

The deposition of terrestrial-derived permafrost particulate organic carbon (POC) has been recorded in major Arctic river deltas. However, associated transport pathways of permafrost POC from the watershed to the coast have not been well constrained. Here we utilized a combination of ramped pyrolysis-oxidation radiocarbon analysis (RPO 14C) along with lignin biomarkers, to track the linkages between soils and river and delta sediments. Surface and deep soils showed distinct RPO thermographs which may be related to degradation and organo-mineral interaction. Soil material in the bed load of the river channel was mostly derived from deep old permafrost. Both surface and deep soils were transported and deposited to the coast. Hydrodynamic sorting and barrier island protection played important roles in terrestrial-derived permafrost POC deposition near the coast. On a large scale, ice processes (e.g., ice gauging and strudel scour) and ocean currents controlled the transport and distribution of permafrost POC on the Beaufort Shelf.

Multiple Deltas Built Out Over Time

NASA Image and Video Library

2014-12-08

This diagram depicts a vertical cross section through geological layers deposited by rivers, deltas and lakes. Deposits from a series of successive deltas build out increasingly high in elevation as they migrate toward the center of the basin.

Yellow River Delta, China

NASA Image and Video Library

2009-12-08

The Yellow River is the second-longest river in China, and the sixth longest in the world and makes many dramatic shifts over time. This image was taken with the ASTER instrument aboard NASA Terra spacecraft in 2009.

Greenhouse gas emissions of different land uses in the delta region of Red River, Vietnam

NASA Astrophysics Data System (ADS)

Zhou, Minghua; Ha, Thu; An, Ngo The; Brüggemann, Nicolas

2017-04-01

Agricultural activities are responsible for up to a third of total anthropogenic GHG emissions. The subtropical/tropical delta areas of the large rivers in Southeast Asia are long-term history agricultural regions in the world. However, due to lack of field measurements, the estimation of the contribution of agro-ecosystems in the subtropical/tropical delta areas to global greenhouse gas emissions remains largely uncertain. Here, we conducted field experiments since January 2016 to quantify greenhouse gases (CO2, CH4 and N2O) emissions from four agricultural land uses of annual rice-rice, rice-vegetable, continuous vegetable system and fish pond in Red River delta region of Vietnam by using the transparent static chamber-gas chromatography technique. Higher N2O emissions were observed in the rice-vegetable and continuous vegetable systems, while lower N2O emissions were observed in the rice-rice and find pond systems. Compared to rice-rice system the cumulative N2O fluxes were on average twenty-fold higher in the rice-vegetable and continuous vegetable systems but significantly lower (75%) in the fish pond. Overall the net CO2 sinks were observed in the rice-rice system while other three land uses of rice-vegetable, continuous vegetable and fish pond acted as the net CO2 sources. The rice-rice and fish pond showed net CH4 emissions while variations of CH4 emissions (i.e. shifting between sources and sinks) along variations of soil moisture and temperature were observed in rice-vegetable and continuous vegetable systems. Compared to rice-rice system, the cumulative CH4 fluxes were significantly decreased by 100% for continuous vegetable system, 94% for rice-vegetable system and 89% for fish pond. Overall, the data suggest that conversion of traditional rice-rice paddy system to rice-vegetable, continuous vegetable system and find pond, which are currently undergoing driven by the economical requests and environmental changes (e.g., salinity intrusion) in this delta

Observational and numerical particle tracking to examine sediment dynamics in a Mississippi River delta diversion

NASA Astrophysics Data System (ADS)

Allison, Mead A.; Yuill, Brendan T.; Meselhe, Ehab A.; Marsh, Jonathan K.; Kolker, Alexander S.; Ameen, Alexander D.

2017-07-01

River diversions may serve as useful restoration tools along coastal deltas experiencing land loss due to high rates of relative sea-level rise and the disruption of natural sediment supply. Diversions mitigate land loss by serving as new sediment sources for land building areas in basins proximal to river channels. However, because of the paucity of active diversions, little is known about how diversion receiving-basins evacuate or retain the sediment required to build new land. This study uses observational and numerical particle tracking to investigate the behavior of riverine sand and silt as it enters and passes through the West Bay diversion receiving-basin located on the lowermost Mississippi River delta, USA. Fluorescent sediment tracer was deployed and tracked within the bed sediment over a five-month period to identify locations of sediment deposition in the receiving-basin and nearby river channel. A computational fluid dynamics model with a Lagrangian sediment transport module was employed to predict selective pathways for riverine flow and sand and silt particles through the receiving-basin. Observations of the fluorescent tracer provides snapshots of the integrated sediment response to the full range of drivers in the natural system; the numerical model results offer a continuous map of sediment advection vectors through the receiving basin in response to river-generated currents. Together, these methods provide insight into local and basin-wide values of sediment retention as influenced by grain size, transport time, and basin morphology. Results show that after two weeks of low Mississippi River discharge, basin silt retention was approximately 60% but was reduced to 4% at the conclusion of the study. Riverine sand retention was approximately near 100% at two weeks and 40% over the study period. Modeled sediment storage was predicted to be greatest at the margins of the primary basin transport pathway; this matched the observed dynamics of the silt