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At least 955 records · Page 53Linked to original sources
USGS1975

Dissolved solids, hardness, and orthophosphate of surface-water runoff in the Suwannee River Water Management District, Florida

This atlas consists of three maps that show the general distri bution of dissolved solids, hardness, and orthophosphate in the streams and lakes within the Suwannee River Water Management District. The atlas was prepared in cooperation with the Water Management District to provide pertinent water-quality information relating to the objectives of the Florida State Water Resources Act of 1972. Under the provisions of this act, the Water Management District is required to establish a regional water-use plan, issue permits for water-use and water-resources related construction, and authorize the export of water. The data presented on these maps will be useful to those concerned with water management and use, in assessing regional water quality, and in estab lishing a base for comparison with future quality data. The ranges of concentration shown on the maps represent maximum concentrations in surface water during the sampling period, January 1965- September 1970. Concentrations are plotted at the sampling sites and are the major criteria for determining the extent of concentration ranges. In some cases the drainage basin boundaries are used in defining concentration range boundaries because the quantity and quality of surface runoff is characteristic of the environment of the basin and may be entirely different from the runoff of adjacent basins. Within drainage basins, individual streams and local drainage divides define concentration boundaries. Some areas, although adjacent to each other in the same basin, have entirely different concentration ranges. For example, an area containing dissolved-solids concentrations in the 0-25 mg/1 (milligrams per litre) range may be adjacent to an area in which concentrations exceed 100 mg/1, as in the southeast part of Jefferson County. Concentration boundaries in these areas were selected by extending each range about halfway between the two sampling sites, as opposed to grading an intermediate range between them without supporting data. As the data are sparse in many areas, regional concentration patterns are generalized and local variations may be expected to exist.

Florida↗
USGS2015

High-resolution remote sensing of water quality in the San Francisco Bay-Delta Estuary

The San Francisco Bay–Delta Estuary watershed is a major source of freshwater for California and a profoundly human-impacted environment. The water quality monitoring that is critical to the management of this important water resource and ecosystem relies primarily on a system of fixed water-quality monitoring stations, but the limited spatial coverage often hinders understanding. Here, we show how the latest technology in visible/near-infrared imaging spectroscopy can facilitate water quality monitoring in this highly dynamic and heterogeneous system by enabling simultaneous depictions of several water quality indicators at very high spatial resolution. The airborne portable remote imaging spectrometer (PRISM) was used to derive high-spatial-resolution (2.6 × 2.6 m) distributions of turbidity, and dissolved organic carbon (DOC) and chlorophyll-a concentrations in a wetland-influenced region of this estuary. A filter-passing methylmercury vs DOC relationship was also developed using in situ samples and enabled the high-spatial-resolution depiction of surface methylmercury concentrations in this area. The results illustrate how high-resolution imaging spectroscopy can inform management and policy development in important inland and estuarine water bodies by facilitating the detection of point- and nonpoint-source pollution, and by providing data to help assess the complex impacts of wetland restoration and climate change on water quality and ecosystem productivity.

California↗
USGS2012

Science to support the understanding of Ohio's water resources

Ohio’s water resources support a complex web of human activities and nature—clean and abundant water is needed for drinking, recreation, farming, and industry, as well as for fish and wildlife needs. The distribution of rainfall can cause floods and droughts, which affects streamflow, groundwater, water availability, water quality, recreation, and aquatic habitats. Ohio is bordered by the Ohio River and Lake Erie and has over 44,000 miles of streams and more than 60,000 lakes and ponds (State of Ohio, 1994). Nearly all the rural population obtain drinking water from groundwater sources. The U.S. Geological Survey (USGS) works in cooperation with local, State, and other Federal agencies, as well as universities, to furnish decisionmakers, policymakers, USGS scientists, and the general public with reliable scientific information and tools to assist them in management, stewardship, and use of Ohio’s natural resources. The diversity of scientific expertise among USGS personnel enables them to carry out large- and small-scale multidisciplinary studies. The USGS is unique among government organizations because it has neither regulatory nor developmental authority—its sole product is reliable, impartial, credible, relevant, and timely scientific information, equally accessible and available to everyone. The USGS Ohio Water Science Center provides reliable hydrologic and water-related ecological information to aid in the understanding of use and management of the Nation’s water resources, in general, and Ohio’s water resources, in particular. This fact sheet provides an overview of current (2012) or recently completed USGS studies and data activities pertaining to water resources in Ohio. More information regarding projects of the USGS Ohio Water Science Center is available at http://oh.water.usgs.gov/.

Ohio↗
USGS2017

Projected impacts of climate, urbanization, water management, and wetland restoration on waterbird habitat in California’s Central Valley

The Central Valley of California is one of the most important regions for wintering waterbirds in North America despite extensive anthropogenic landscape modification and decline of historical wetlands there. Like many other mediterranean-climate ecosystems across the globe, the Central Valley has been subject to a burgeoning human population and expansion and intensification of agricultural and urban development that have impacted wildlife habitats. Future effects of urban development, changes in water supply management, and precipitation and air temperature related to global climate change on area of waterbird habitat in the Central Valley are uncertain, yet potentially substantial. Therefore, we modeled area of waterbird habitats for 17 climate, urbanization, water supply management, and wetland restoration scenarios for years 2006–2099 using a water resources and scenario modeling framework. Planned wetland restoration largely compensated for adverse effects of climate, urbanization, and water supply management changes on habitat areas through 2065, but fell short thereafter for all except one scenario. Projected habitat reductions due to climate models were more frequent and greater than under the recent historical climate and their magnitude increased through time. After 2065, area of waterbird habitat in all scenarios that included severe warmer, drier climate was projected to be >15% less than in the “existing” landscape most years. The greatest reduction in waterbird habitat occurred in scenarios that combined warmer, drier climate and plausible water supply management options affecting priority and delivery of water available for waterbird habitats. This scenario modeling addresses the complexity and uncertainties in the Central Valley landscape, use and management of related water supplies, and climate to inform waterbird habitat conservation and other resource management planning. Results indicate that increased wetland restoration and additional conservation and climate change adaptation strategies may be warranted to maintain habitat adequate to support waterbirds in the Central Valley.

California↗
USGS2016

Science to support the understanding of Ohio's water resources, 2016-17

Ohio’s water resources support a complex web of human activities and nature—clean and abundant water is needed for drinking, recreation, farming, and industry, as well as for fish and wildlife needs. Although rainfall in normal years can support these activities and needs, occasional floods and droughts can disrupt streamflow, groundwater, water availability, water quality, recreation, and aquatic habitats. Ohio is bordered by the Ohio River and Lake Erie; it has over 44,000 miles of streams and more than 60,000 lakes and ponds (State of Ohio, 1994). Nearly all of the rural population obtains drinking water from groundwater sources. The U.S. Geological Survey (USGS) works in cooperation with local, State, and other Federal agencies, as well as universities, to furnish decisionmakers, policy makers, USGS scientists, and the general public with reliable scientific information and tools to assist them in management, stewardship, and use of Ohio’s natural resources. The diversity of scientific expertise among USGS personnel enables them to carry out large- and small-scale multidisciplinary studies. The USGS is unique among government organizations because it has neither regulatory nor developmental authority—its sole product is impartial, credible, relevant, and timely scientific information, equally accessible and available to everyone. The USGS Ohio Water Science Center provides reliable hydrologic and water-related ecological information to aid in the understanding of the use and management of the Nation’s water resources, in general, and Ohio’s water resources, in particular. This fact sheet provides an overview of current (2016) or recently completed USGS studies and data activities pertaining to water resources in Ohio. More information regarding projects of the USGS Ohio Water Science Center is available at http://oh.water.usgs.gov/ .

Ohio↗
USGS2014

Science to support the understanding of Ohio's water resources, 2014-15

Ohio’s water resources support a complex web of human activities and nature—clean and abundant water is needed for drinking, recreation, farming, and industry, as well as for fish and wildlife needs. Although rainfall in normal years can support these activities and needs, occasional floods and droughts can disrupt streamflow, groundwater, water availability, water quality, recreation, and aquatic habitats. Ohio is bordered by the Ohio River and Lake Erie; it has over 44,000 miles of streams and more than 60,000 lakes and ponds. Nearly all the rural population obtain drinking water from groundwater sources. The U.S. Geological Survey (USGS) works in cooperation with local, State, and other Federal agencies, as well as universities, to furnish decision makers, policy makers, USGS scientists, and the general public with reliable scientific information and tools to assist them in management, stewardship, and use of Ohio’s natural resources. The diversity of scientific expertise among USGS personnel enables them to carry out large- and small-scale multidisciplinary studies. The USGS is unique among government organizations because it has neither regulatory nor developmental authority—its sole product is impartial, credible, relevant, and timely scientific information, equally accessible and available to everyone. The USGS Ohio Water Science Center provides reliable hydrologic and water-related ecological information to aid in the understanding of the use and management of the Nation’s water resources, in general, and Ohio’s water resources, in particular. This fact sheet provides an overview of current (2014) or recently completed USGS studies and data activities pertaining to water resources in Ohio. More information regarding projects of the USGS Ohio Water Science Center is available at http://oh.water.usgs.gov/ .

Ohio↗
USGS2024

Assessing influence from wastewater treatment facilities on Glorieta Creek and the Pecos River within Pecos National Historical Park, New Mexico, February–October 2022

The Pecos National Historical Park protects 2.9 miles of the Pecos River and part of Glorieta Creek within the park boundaries. Updated water-quality data can assist resource managers in determining if effluent from two nearby wastewater treatment plants (WWTPs) is affecting the quality of the water in the Pecos River and Glorieta Creek within the park. Water samples were collected four times in 2022 at two WWTP outfalls, two locations on Glorieta Creek, and two locations on the Pecos River. Water quality parameters (dissolved oxygen, water temperature, pH, turbidity, specific conductance) were measured in the field, and samples were collected and analyzed for major ions, trace elements, rare earth elements, nutrients, bacteria, and per- and polyfluoroalkyl substances (PFAS). Specific conductance values in all samples collected from Glorieta Creek exceeded the New Mexico Surface Water Quality Standard (NMWQS) of 300 microsiemens per centimeter at 25 degrees Celsius. Concentrations of dissolved oxygen in three samples collected from Glorieta Creek and one sample for the Pecos WWTP did not meet the standard for high-quality cold-water use. Concentrations of Escherichia coli in samples from the Pecos WWTP exceeded the NMWQS of 235 colony-forming units per 100 milliliters during every sampling event. Concentrations of E. coli in samples collected from two sites on Glorieta Creek in August exceeded the NMWQS. The chemical signature of water from Glorieta Creek indicated groundwater and (or) septic system contributions. Water samples collected from the Pecos River all had similar chemical signatures of calcium-bicarbonate type. Although concentrations of several trace elements were higher in samples from Glorieta Creek than in samples from the Pecos River, no concentrations exceeded the drinking-water standards. No concentrations exceeded aquatic life standards except for copper concentrations in two samples from the downstream location on Glorieta Creek. The trace element signature and the gadolinium anomalies in the WWTP samples indicate anthropogenic contributions. Eleven of the 28 PFAS compounds analyzed were detected in samples during this study, with the treated wastewater effluent samples having the highest total PFAS concentrations. The total PFAS concentrations in samples from Glorieta Creek decreased by an order of magnitude as the creek flowed downstream. At the downstream site on the Pecos River, there was only one sample that had a detection of PFAS.

New Mexico↗
USGS1982

A national water-use information program

The U.S. Geological Survey has compiled estimates of water use every five years since 1950. These estimates have been derived from many sources, and have a wide range of accuracy. Therefore, they fall short of providing a national data base that is both current and reliable. In 1977, the Congress of the United States recognized the need for uniform information on water use and directed the U.S. Geological Survey to establish a National Water-Use Information Program to complement the Survey's data on the availability and quality of the Nation's water resources. The National Water-Use Information Program was designed as a cooperative program between the States and the Federal Government. The goals of the program are: to collect and compile water-use data; to develop and refine computerized water-use data systems at both the State and national levels; to devise new methods and techniques to improve the collection and analysis of water-use information; and to disseminate this information to those involved in establishing water-resources policy and to those managing the resources. The program that started in 1978 in 20 States now includes participation by 47 States. Water-Use information is being compiled for 12 categories of use. Each State will have a automated data system that contains site-specific information about the water use in each category. The National Water-Use Data System will contain information for the 12 categories of use summarized by counties and river basins within each State. The national system will aid in defining how much fresh and saline surface water and ground water is withdrawn and for what purpose, how much water is consumed during use, and how much water is returned to a water body (stream, lake, or aquifer) after use.

Open-File Report↗
USGS2021

The basin characterization model—A regional water balance software package

This report documents the computer software package, Basin Characterization Model, version 8 (BCMv8)—a monthly, gridded, regional water-balance model—and provides detailed operational instructions and example applications. After several years of many applications and uses of a previous version, CA-BCM, published in 2014, the BCMv8 was refined to improve the accuracy of the water-balance components, particularly the recharge estimate, which is the most difficult to accurately assess. The improvement of the various water-balance components targeted the actual evapotranspiration component, which, in turn, reduced the uncertainty of the recharge estimate. The improvement of this component was enabled by the availability of a national, gridded actual-evapotranspiration product from the U.S. Geological Survey that was unique in its scope to combine remotely sensed spatial variability and ground-based long-term water-balance constraints. This dataset provided the ability to assess monthly actual evapotranspiration for 62 vegetation types and to perform regional calibration in watersheds throughout California with the objective of closing the water balance using improved estimates for each component. The refinements, including vegetation-specific evapotranspiration, enabled the development of applications that could explore various aspects of landscape disturbance, such as wildfire, forest management, or urbanization. The improvements to BCMv8 also provided the ability to assess long-term sustainability of water resources under a variety of management applications or future climate projections.

California↗
USGS1984

Water resources of the Palau Islands

The Palau Islands are a group of 350 islands, ranging in size from a few hundred square feet to the 153-square-mile island of Babelthuap. Babelthuap is the second largest island in the Western Pacific and comprises more than 80 percent of the total land area of the Palau Islands. Most of the islands are uninhabited limestone ridges covered with dense vegetation. These islands have no freshwater resources and are not included in this report. The island of Koror with an area of 3.6 square miles is the administrative, commercial, and population center of Palau and has an annual average rainfall of 148 inches. Short-term rainfall records at other locations in the islands indicate little variation in annual rainfall throughout the Palau Islands. Runoff-to-rainfall ratios for streams on Babelthuap show that about 70 percent of the rain falling on the island runs off to the ocean. The uniformity of rainfall and basin characteristics is shown by the excellent correlation between mean annual rainfall on Koror and streamflow on Babelthuap and by the close correlations between discharge at gaging stations and partial-record sites. Surface water quality is generally very good as shown by 55 chemical analyses of water from 18 sources. The dissolved solids concentration of water samples did not exceed 66 milligrams per liter. This report summarizes in one volume hydrologic data collection in a 14-year period of study and provides interpretations of the data than can be used by planners and public works officials as a basis for making decisions on the development and management of the islands' water resources.

Water-Resources Investigations Report↗
USGS2023

Evaluation of stream capture related to groundwater pumping, Lower Humboldt River Basin, Nevada

The Humboldt River Basin is the only river basin that is contained entirely within the State of Nevada. The effect of groundwater pumping on the Humboldt River is not well understood. Tools are needed to determine stream capture and manage groundwater pumping in the Humboldt River Basin. The objective of this study is to estimate capture and storage change caused by groundwater withdrawals in the lower Humboldt River Basin that can provide the Nevada State Engineer with data and information needed to manage groundwater and surface-water resources. A numerical groundwater flow model was developed for the purpose of estimating stream capture from pre-2016 and future pumping as well as for any location of potential future pumping within the lower Humboldt River Basin. This model was developed using MODFLOW-NWT to represent the lower Humboldt River Basin hydrologic system, including Humboldt River; Rye Patch Reservoir; groundwater evapotranspiration; pumping from municipal, agricultural, mining, and domestic wells; and agricultural drains. Aquifer properties were calibrated using results from numerous single- and multi-well aquifer tests (Nadler, 2020) and through the process of model calibration. Historical capture was estimated for 1960–2016 and predictive capture for the system was projected 100 years into the future (2017–2116) based on historical pumping patterns. Stream capture and drain capture are relatively low for the historical and predictive periods. During the historical period, increased pumping during dry years caused increased connections with capture sources and less water sourced to wells from aquifer storage. Storage and groundwater levels generally recovered during subsequent wet years. Overall, storage change has been the main source of water to wells in the lower Humboldt River Basin, followed by groundwater evapotranspiration capture. During the predictive period, pumping is projected to remain constant and capture 9 percent of stream water after 100 years. Capture and storage change maps were created to visualize spatial variability in potential capture and storage change through time and to provide a database of results that can be used to manage groundwater and surface-water resources. These maps show that potential stream capture would be a minor source of water to wells located across most of the simulated area, except for locations close to the Humboldt River and Rye Patch Reservoir. Drains also would be a minor potential source of water to wells except for those directly adjacent to the drains. In general, the potential supply of water to wells is storage-dominated and over time groundwater evapotranspiration-dominated in the agricultural area. Capture difference maps were generated to visualize where potential capture results might have greater limitations associated with nonlinear flow processes, such as head-dependent boundary conditions. Higher capture differences indicate larger capture map bias and therefore greater capture map uncertainty due to the inability of capture maps to account for nonlinear flow processes. Stream capture differences are highest directly adjacent to the river but are otherwise minimal. Drain capture differences are highest in the region of the agricultural drain network but are otherwise minimal. The Humboldt River, Rye Patch Reservoir, and drains introduce very little nonlinearity to the model, and their associated capture map bias is minimal. Potential groundwater evapotranspiration capture introduces a fair amount of nonlinearity to the model and has the potential to result in significant, localized groundwater evapotranspiration capture map bias over time. Groundwater evapotranspiration capture differences are the result of higher pumping rates lowering the water table below the root zone faster than lower pumping rates and essentially removing groundwater evapotranspiration as a potential source of capture faster than lower pumping rates. Wells that can no longer source their supply through groundwater evapotranspiration capture then generally source more of their water from storage. Thus, storage change bias increases over time as well. Capture prediction uncertainty due to parameter estimation was evaluated using a covariance matrix adaptation-evolution strategy. One hundred Monte Carlo realizations of model parameters were applied to the model to assess capture uncertainty at 13 grid cell locations within the model domain. In general, results indicated that greater capture uncertainty for a given source (river, drains, or evapotranspiration) is associated with proximity of a pumping well to that source. The magnitude of maximum capture fraction uncertainties after 100 years of pumping for stream capture, drain capture, groundwater evapotranspiration capture, and storage change were plus or minus (±) 0.17, ±0.10, ±0.20, and ±0.22, respectively.

Nevada↗
USGS2000

The history of stream gaging in Ohio

Introduction Streams are a natural resource that can influence economic growth and the development of communities. They supply water for many uses, provide habitat for aquatic plants and animals, and sup-port recreational activities such as boat-ing and fishing. The amount of water (flow) in a stream — either too little or too much — can seriously affect these uses and human life. By using a method called stream gaging , information about the flow in a stream and the fluctuations in that flow can be obtained. n its simplest form, stream gaging may consist of measuring any number of the following stream characteristics: stage (or depth), cross-sectional area, velocity, and (or) flow (or discharge). When the depth and velocity are measured at several points across the stream channel so that the flow (or discharge ) is calculated, a streamflow measurement (or discharge measurement ) is made. By making streamflow measurements at the same site on a stream over a wide range of stages, a relation between stage and discharge can be developed. This relation can be used to provide information on the magnitude and fluctuations of flow on a stream. If long-term or continuous information is needed on a specific site, a stream-gaging station can be established. A stream-gaging station is a site where stage is monitored and recorded and streamflow measurements are made to provide a stage-discharge relation. Ever since the first documented streamflow measurement was made in Ohio — on the Sandusky River — stream-gaging information has been used to minimize the effects of floods and droughts, determine locations for water intakes and wastewater-treatment plants, and provide data for many other uses. Today, stream gaging is a routine activity in managing the State’s water resources.

Ohio↗
USGS2015

The 3D Elevation Program: summary for Pennsylvania

Elevation data are essential to a broad range of applications, including forest resources management, wildlife and habitat management, national security, recreation, and many others. For the Commonwealth of Pennsylvania, elevation data are critical for natural resources conservation (including the effects of drilling for oil and natural gas), agriculture and precision farming, flood risk management, infrastructure and construction management, water supply and quality, geologic resource assessment and hazard mitigation, and other business uses. Today, high-density light detection and ranging (lidar) data are the primary sources for deriving elevation models and other datasets. Federal, State, and local agencies work in partnership to replace data that are older and of lower quality. A joint goal of Commonwealth and Federal partners is to provide a temporal and density refresh of the current statewide coverage in order to support existing and emerging applications enabled by improved lidar data. The National Enhanced Elevation Assessment evaluated multiple elevation data acquisition options to determine the optimal data quality and data replacement cycle relative to cost to meet the identified requirements of the user community. The evaluation demonstrated that lidar acquisition at quality level 2 for the conterminous United States and quality level 5 interferometric synthetic aperture radar (ifsar) data for Alaska with a 6- to 10-year acquisition cycle provided the highest benefit/cost ratios. The 3D Elevation Program (3DEP) initiative selected an 8-year acquisition cycle for the respective quality levels. 3DEP, managed by the U.S. Geological Survey, the Office of Management and Budget Circular A–16 lead agency for terrestrial elevation data, responds to the growing need for high-quality topographic data and a wide range of other 3D representations of the Nation’s natural and constructed features.

Pennsylvania↗
USGS1996

Ground-water and stream-water interaction in the Owl Creek basin, Wyoming

Understanding of the interaction of ground-water and surface-water resources is vital to water management when water availability is limited.Inflow of ground water is the primary source ofwater during stream base flow. The water chemistry of streams may substantially be affected by that inflow of ground water. This report is part of a study to examine ground-water and surface-water interaction in the Owl Creek Basin, Wyoming, completed by the U.S. Geological Survey incooperation with the Northern Arapaho Tribe and the Shoshone Tribe. During a low flow period between November\x1113 - 17, 1991, streamflowmeasurements and water-quality samples were collected at 16 selected sites along major streams and tributaries in the Owl Creek Basin,Wyoming. The data were used to identify stream reaches receiving ground-water inflow and to examine causes of changes in stream chemistry.Streamflow measurements, radon-222 activity load, and dissolved solids load were used to identified stream reaches receiving ground-water inflow.Streamflow measurements identified three stream reaches receiving ground-water inflow. Analysis of radon-222 activity load identified five stream reaches receiving ground-water inflow. Dissolvedsolids load identified six stream reaches receiving ground-water inflow. When these three methods were combined, stream reaches in two areas, theEmbar Area and the Thermopolis Anticline Area, were identified as receiving ground-water inflow.The Embar Area and the Thermopolis Anticline Area were then evaluated to determine the source of increased chemical load in stream water. Three potential sources were analyzed: tributary inflow, surficial geology, and anticlines. Two sources,tributary inflow and surficial geology, were related to changes in isotopic ratios and chemical load in the Embar Area. In two reaches in the Embar Area, isotopic ratios of 18O/16O, D/H, and 34S/32S indicated that tributary inflow affected stream-water chemistry. Increased chemical load of dissolved solids and dissolved sulfate in North Fork andSouth Fork Owl Creek appear to be related to the percentage of unconsolidated Quaternary deposits and of Cretaceous-Jurassic deposits in the drainage area. In the Thermopolis Anticline Area, changes in water chemistry in Owl Creek were not related to tributary inflow, surficial geology, or anticlines.The three tributaries that flow into Owl Creek in the Thermopolis Anticline Area did not substantially affect the isotopic ratios or contribute to the chemical load. Changes in the chemical load were not associated with changes in the surficial geologybetween the stream-water sampling sites. Water levels and chemical ratios indicate no ground-water inflow from the Thermopolis Anticline geothermal system to Owl Creek.

Water-Resources Investigations Report↗
USGS2011

Selenium in aquatic biota inhabiting agricultural drains in the Salton Sea Basin, California

Resource managers are concerned that water conservation practices in irrigated farmlands along the southern border of the Salton Sea, Imperial County, California, could increase selenium concentrations in agricultural drainwater and harm the desert pupfish ( Cyprinodon macularius ), a federally protected endangered species. As part of a broader attempt to address this concern, we conducted a 3-year investigation to collect baseline information on selenium concentrations in seven agricultural drains inhabited by pupfish. We collected water, sediment, selected aquatic food-chain taxa (particulate organic detritus, filamentous algae, net plankton, and midge [Chironomidae] larvae), and two poeciliid fishes (western mosquitofish Gambusia affinis and sailfin molly Poecilia latipinna ) for selenium determinations. The two fish species served as ecological surrogates for pupfish, which we were not permitted to sacrifice. Dissolved selenium ranged from 0.70 to 32.8 μg/L, with selenate as the major constituent. Total selenium concentrations in other environmental matrices varied widely among drains, with one drain (Trifolium 18) exhibiting especially high concentrations in detritus, 5.98–58.0 μg Se/g; midge larvae, 12.7–50.6 μg Se/g; mosquitofish, 13.2–20.2 μg Se/g; and mollies, 12.8–30.4 μg Se/g (all tissue concentrations are based on dry weights). Although toxic thresholds for selenium in fishes from the Salton Sea are still poorly understood, available evidence suggests that ambient concentrations of this element may not be sufficiently elevated to adversely affect reproductive success and survival in selenium-tolerant poeciliids and pupfish.

Environmental Monitoring and Assessment↗
USGS2012

Complexity of human and ecosystem interactions in an agricultural landscape

The complexity of human interaction in the commercial agricultural landscape and the resulting impacts on the ecosystem services of water quality and quantity is largely ignored by the current agricultural paradigm that maximizes crop production over other ecosystem services. Three examples at different spatial scales (local, regional, and global) are presented where human and ecosystem interactions in a commercial agricultural landscape adversely affect water quality and quantity in unintended ways in the Delta of northwestern Mississippi. In the first example, little to no regulation of groundwater use for irrigation has caused declines in groundwater levels resulting in loss of baseflow to streams and threatening future water supply. In the second example, federal policy which subsidizes corn for biofuel production has encouraged many producers to switch from cotton to corn, which requires more nutrients and water, counter to national efforts to reduce nutrient loads to the Gulf of Mexico and exacerbating groundwater level declines. The third example is the wholesale adoption of a system for weed control that relies on a single chemical, initially providing many benefits and ultimately leading to the widespread occurrence of glyphosate and its degradates in Delta streams and necessitating higher application rates of glyphosate as well as the use of other herbicides due to increasing weed resistance. Although these examples are specific to the Mississippi Delta, analogous situations exist throughout the world and point to the need for change in how we grow our food, fuel, and fiber, and manage our soil and water resources.

Arkansas, Louisiana, Mississippi, Missouri↗
USGS2019

Water-quality trends in U.S. rivers, 2002 to 2012: Relations to levels of concern

Effective management and protection of water resources relies upon understanding how water-quality conditions are changing over time. Water-quality trends for ammonia, chloride, nitrate, sulfate, total dissolved solids (TDS), total nitrogen (TN) and total phosphorus (TP) were assessed at 762 sites located in the conterminous United States between 2002 and 2012. Annual mean concentrations at the start and end of the trend period were compared to an environmentally meaningful level of concern (LOC) to categorize patterns in water-quality changes. Trend direction, magnitude, and the proximity of concentrations to LOCs were investigated. Of the 1956 site-constituent combinations investigated, 30% were above the LOC in 2002, and only six (0.3%) crossed the LOC threshold, either from above or below, indicating that waterquality conditions are not substantially improving, nor are they degrading, in relation to the LOCs. The concentrations of ammonia, nitrate, sulfate, chloride, and TDS tended to be below the LOC, and in cases where the trend was increasing (concentrations approached the LOC from below), the increases were varied and small in magnitude. In contrast, concentrations of TN and TP tended to be above the LOC, and where the trend was decreasing (concentrations approached the LOC from above), the decreases were larger in magnitude and more consistent. These results indicate that if water-quality conditions continue to trend in the same direction, at the same rate, for all sites and constituents studied, elevated concentrations are more likely to drop below an LOC before low concentrations will exceed an LOC.

Science of the Total Environment↗
USGS2013

Tamarix, hydrology and fluvial geomorphology

This chapter explores the impact of hydrology and fluvial geomorphology on the distribution and abundance of Tamarix as well as the reciprocal effects of Tamarix on hydrologic and geomorphic conditions. It examines whether flow-regime alteration favors Tamarix establishment over native species, and how Tamarix stands modify processes involved in the narrowing of river channels and the formation of floodplains. It begins with an overview of the basic geomorphic and hydrologic character of rivers in the western United States before analyzing how this setting has contributed to the regional success of Tamarix . It then considers the influence of Tamarix on the hydrogeomorphic form and function of rivers and concludes by discussing how a changing climate, vegetation management, and continued water-resource development affect the future role of Tamarix in these ecosystems.

Book chapter↗