74 research outputs found
A synthesis of aquatic science for management of Lakes Mead and Mohave: U.S. Geological Survey Circular 1381
No full textLake Mead provides many significant benefits that have made the modern development of the southwestern United States possible. The lake also provides important aquatic habitat for a wide variety of wildlife including endangered species, and a diversity of world-class water based recreational opportunities for more than 8 million visitors annually. It is one of the most extensively used and intensively monitored reservoirs in the United States. The largest reservoir by volume in the United States, it supplies critical storage of water supplies for more than 25 million people in three western states (California, Arizona, and Nevada). Storage within Lake Mead supplies drinking water and the hydropower to provide electricity for major cities including Las Vegas, Phoenix, Los Angeles, Tucson, and San Diego, and irrigation of greater than 2.5 million acres of croplands.
Due to the importance of Lake Mead, multiple agencies are actively involved in its monitoring and research. These agencies have a long history of collaboration in the assessment of water quality, water-dependent resources, and ecosystem health. In 2004, the National Park Service obtained funds from the Southern Nevada Public Lands Management Act to enhance this partnership and expand monitoring and research efforts to increase the overall understanding of Lake Mead and Lake Mohave. Participating agencies included the National Park Service, Southern Nevada Water Authority, U.S. Geological Survey, Nevada Department of Wildlife, Bureau of Reclamation, U.S. Fish and Wildlife Service, University of Nevada, Las Vegas, and University of Nevada, Reno.
Results of these important efforts have been presented in Lake Mead Science Symposia conducted in 2009 and 2012. The relationships forged by the collaboration led to the development in 2012 of the Lake Mead Ecosystem Monitoring (LaMEM) Work Group, which has formalized the partnership and documented an interagency purpose and mission statement with common objectives for protection of Lake Mead and Lake Mohave water quality and water-dependent resources. This Circular has been developed to summarize the state of the knowledge related to the interests and objectives of the LaMEM Work Group, to inform management and the public of current lake conditions, and identify future needs for monitoring and research. It is hoped that this report will provide a framework for continued long-term investigations and analysis of the environmental health of Lakes Mead and Mohave
Compositions of groundwater samples from shallow aquifer in southwest Bangladesh
No full textSamples collected from tubewells in May and October of years 2012 and 2013. Data in Microsoft Excel 2016 format. Tubewell locations in "Locations" tab, compositional data in "Data" tab.
Data used in the following publication:
Ayers J. C., Goodbred S., George G., Fry D., Benneyworth L., Hornberger G., Roy K., Karim M. R. and Akter F. (2016) Sources of salinity and arsenic in groundwater in southwest Bangladesh. Geochem. Trans. 17, 1–22. Available at: http://dx.doi.org/10.1186/s12932-016-0036-6
Compositions of groundwater samples from shallow aquifer in southwest Bangladesh
No full textSamples collected from tubewells in May and October of years 2012 and 2013. Data in Microsoft Excel 2016 format. Tubewell locations in "Locations" tab, compositional data in "Data" tab.
Data used in the following publication:
Ayers J. C., Goodbred S., George G., Fry D., Benneyworth L., Hornberger G., Roy K., Karim M. R. and Akter F. (2016) Sources of salinity and arsenic in groundwater in southwest Bangladesh. Geochem. Trans. 17, 1–22. Available at: http://dx.doi.org/10.1186/s12932-016-0036-6
Holocene environmental change recorded in lagoonal sediment proxies at Huaca Prieta, north coastal Peru
No full textThis study attempts to define the early to mid-Holocene paleoenvironment at Huaca Prieta, an archaeological site on the north coast of Peru, through a combination of sedimentological, paleoecological, and stable isotope analyses. This research is part of a larger collaborative study drawing on many disciplines, and the interpretations of the results presented here are solely from a geological perspective. Multiple studies point to a severely diminished or even absent El Niño in the region during the mid-Holocene, but the Chicama River valley is a relatively unstudied location. Sediment coring from the upper 6 m reveals laminated to thinly bedded carbonates, organic sediments, and fine-grained clays deposited within larger intervals of sands and silts. These finer-grained sediments evidence a coastal lagoon 3 km in length which existed approximately 7300-6200 cal ybp. Stratigraphic analysis of the upper 6 m of sediments reveals a marked decrease in siliciclastic material delivered to the floodplain during this time, with potential implications for the mid-Holocene El Niño frequency debate and human-environment linkages during this time
Perceptions of Water Quality in Southwestern Bangladesh
No full textEarth and Environmental Sciences
Perceptions of Water Quality in Southwestern Bangladesh
Rachel Shumaker
Thesis under the direction of Professor Jonathan M. Gilligan
Increasing stress on Southwestern Bangladesh has raised concerns about the well-being of the many people living in rural villages living in this region. This has led researchers to focus on the primary source of stress: water quality and water scarcity. However, the dynamic nature of the land and people of Bangladesh require a more interdisciplinary approach when exploring perceptions of water quality access to safe drinking water is affected not only by the chemistry of the water, but also the politics governing access to water and the psychology of people’s perceptions of drinking water. Lack of reliable year-round drinking water sources, coupled with salinity, arsenic contamination, and conversion of paddy fields to shrimp farms all contribute to water scarcity in coastal regions of Bangladesh. In our study area, we found that most people do not have access to safe drinking water, regardless of social or economic status. Despite the poor quality of the drinking water, most people think their water tastes good, so there is a mismatch in perceptions of both taste and saltiness, and water quality. The perception of water quality is not affected by socio-economic status, religion, or gender, and water security remains a challenge even for the relatively well to do.
Approved:
Jonathan Gilligan, Ph.D
Identifying land use changes and coal mining impacts on water quality: A case study across time and space
No full textGroundwater-Surface Water Interactions in the Tidally-Dominated Coastal Region of the Bengal Basin: A One-Dimensional Numerical Analysis of Tidal and Surface Water Controls on Local Aquifer Systems
No full textClimate change and sea level rise will continue to stress the human and natural landscapes over the next century with low-lying deltaic regions characterized by extensive aquifer systems being highly vulnerable to these perturbations. Specifically, groundwater and surface water interactions may be adversely affected by the estimated rise (56-200 cm) in sea level through aquifer salinization. The Bengal Basin is one of the most densely populated of these regions with brackish groundwater already an issue in the tidally-dominated reaches near the Bay of Bengal. Previous studies suggest the groundwater system is isolated from the surface water system with the brackish groundwater being of Pleistocene age. Here, we employed a one-dimensional finite-difference model of a conceptualized aquifer system between two tidal channels in an attempt to discern groundwater and surface water connectivity. The model varied aquifer transmissivity (TA), channel transmissivity (TC), aquifer storativity (S), and tidal range (TR) over a realistic range of values. The dominant control on connectivity was found to be hydraulic diffusivity (TA/S and TC/S). The results suggest some degree of hydraulic connectivity between the aquifer and tidal systems is possible under present conditions. These results call for a reevaluation of our understanding of groundwater-surface water dynamics in the region and may influence our mitigation strategies in the face of climate change
Palaeosol Control of Arsenic Pollution: The Bengal Basin in West Bengal, India
No full textGroundwater in the Bengal Basin is badly polluted by arsenic (As) which adversely affects human health. To provide low-As groundwater for As mitigation, it was sought across 235 km2 of central West Bengal, in the western part of the basin. By drilling 76 boreholes and chemical analysis of 535 water wells, groundwater with <10 µg/L As in shallow aquifers was found under one-third of a study area. The groundwater is in late Pleistocene palaeo-interfluvial aquifers of weathered brown sand that are capped by a palaeosol of red clay. The aquifers form two N-S trending lineaments that are bounded on the east by an As-polluted deep palaeo-channel aquifer and separated by a shallower palaeo-channel aquifer. The depth to the top of the palaeo-interfluvial aquifers is mostly between 35 and 38 m below ground level (mbgl). The palaeo-interfluvial aquifers are overlain by shallow palaeo-channel aquifers of gray sand in which groundwater is usually As-polluted. The palaeosol now protects the palaeo-interfluvial aquifers from downward migration of As-polluted groundwater in overlying shallow palaeo-channel aquifers.
The depth to the palaeo-interfluvial aquifers of 35 to 38 mbgl makes the cost of their exploitation affordable to most of the rural poor of West Bengal, who can install a well cheaply to depths up to 60 mbgl. The protection against pollution afforded by the palaeosol means that the palaeo-interfluvial aquifers will provide a long-term source of low-As groundwater to mitigate As pollution of groundwater in the shallower, heavily used, palaeo-channel aquifers. This option for mitigation is cheap to employ and instantly available
Groundwater-Surface Water Interactions in the Tidally-Dominated Coastal Region of the Bengal Basin: A One-Dimensional Numerical Analysis of Tidal and Surface Water Controls on Local Aquifer Systems
No full textIdentifying land use changes and coal mining impacts on water quality: A case study across time and space
No full textThe spatial and temporal variability of water chemistry complicates the process of observing and identifying changes to water quality, particularly in catchments where data are spare. In this study, the effect of coal mining on water quality was assessed for the New River and upland, sub-catchment Indian Fork, in eastern Tennessee. Through the use of fragmented water quality and discharge records, hydrochemical trends were identified and compared between catchments and across time. Concentration-discharge relationships were characterized and recursive time-series modeling was completed to quantify long and short term hydrochemical trends. The inability of the New River 2007 time-series model to accurately perform under 1980 low-flow conditions suggests the basin wide shift in reclamation practices during the 1980s affected hydrologic pathways. Little temporal change was anticipated for the Indian Fork as mining ceased prior to available data, however hydrochemistry shifted from chemostatic to dilution response, likely due to spatial heterogeneity of the stream. The hydrochemical spatial disparity between the catchments is likely attributable to the percent of mining disturbed area within the New River (~7%) and Indian Fork (23%). Alternating c-Q loop rotation in the New River was found to be dependent on peak flows above (CW) or below (CCW) 25 m3/s discharge. Due to the magnitude of disturbance, the Indian Fork is conceptualized as a two component system: (1) impacted (i.e. spoil water) and (2) non-impacted water. The New River is conceptualized as a three component system: (1) impacted water, (2) non-impacted water, and (3) event water
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