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USGS2020

Spatially referenced models of streamflow and nitrogen, phosphorus, and suspended-sediment loads in the southeastern United States

Spatially Referenced Regression On Watershed attributes (SPARROW) models were applied to describe and estimate mean-annual streamflow and transport of total nitrogen (TN), total phosphorus (TP), and suspended sediment (SS) in streams and delivered to coastal waters of the southeastern United States on the basis of inputs and management practices centered near 2012, the base year of the model. Previously published TN and TP models for 2002 served as a starting point and reference for comparison. The datasets developed for the 2012 models not only represent updates of previous conditions but also incorporate new approaches for characterizing sources and transport processes that were not available for previous models. Variability in streamflow across the southeastern United States was explained as a function of precipitation adjusted for evapotranspiration, spring discharge, and municipal and domestic wastewater discharges to streams. Results from the streamflow model were used as input to the water-quality SPARROW models, and areas with large streamflow prediction errors—urban areas and karst areas—were used to provide guidance on where additional data are needed to improve routing of flow. Variability in TN transport in Southeast streams was explained by the following five sources in order of decreasing mass contribution to streams: atmospheric deposition, agricultural fertilizer, municipal wastewater, manure from livestock, and urban land. Variable rates of TN delivery from source to stream were attributed to variation among catchments in climate, soil texture, and vegetative cover, including the extent of cover crops in the watershed. Variability in TP transport in Southeast streams was explained by the following six sources in order of decreasing mass contribution to streams: parent-rock minerals, urban land, manure from livestock, municipal wastewater, agricultural fertilizer, and phosphate mining. Varying rates of TP delivery were attributed to variation in climate, soil erodibility, depth to water table, and the extent of conservation tillage practices in the watershed. Variability in SS transport in Southeast streams was explained by variable sediment export rates for different combinations of land cover and geologic setting (for upland sources of sediment) and by gains in stream power caused by longitudinal changes in channel hydraulics (for channel sources of sediment). Sediment yields for the transitional land cover (shrub, scrub, herbaceous, and barren) varied widely depending on geologic setting and on agricultural land cover. Varying rates of SS delivery, like those for TP, were attributed to variation in climate, soil erodibility, and the extent of conservation tillage practices in the watershed, as well as to areal extent of canopy land cover in the 100-meter buffer along the channel. Relatively large uncertainty, compared to the other three models, for almost all the SS source coefficients indicates the need for caution when interpreting the results from the sediment model. TN, TP, and SS inputs to streams from sources were balanced in the models with losses from physical processes in streams and reservoirs and with water withdrawals. The losses in streams and reservoirs along with withdrawals removed 35, 44, and 65 percent of the TN, TP, and SS load, respectively, that entered streams before reaching coastal waters.

Scientific Investigations Report↗
USGS1995

Land use and water use in the Antelope Valley, California

Urban land use and water use in the Antelope Valley, California, have increased significantly since development of the valley began in the late 1800's.. Ground water has been a major source of water in this area because of limited local surface-water resources. Ground-water pumpage is reported to have increased from about 29,000 acre-feet in 1919 to about 400,000 acre-feet in the 1950's. Completion of the California Aqueduct to this area in the early 1970's conveyed water from the Sacramento-San Joaquin Delta, about 400 miles to the north. Declines in groundwater levels and increased costs of electrical power in the 1970's resulted in a reduction in the quantity of ground water that was pumped annually for irrigation uses. Total annual reported ground-water pumpage decreased to a low of about 53,200 acre-feet in 1983 and increased to about 91,700 acre-feet in 1991 as a result of rapid urban development and the 1987-92 drought. This increased urban development, in combination with several years of drought, renewed concern about a possible return to extensive depletion of ground-water storage and increased land subsidence. Increased water demands are expected to continue as a result of increased urban development. Water-demand forecasts in 1980 for the Antelope Valley indicated that total annual water demand by 2020 was expected to be about 250,000 acre-feet, with agricultural demand being about 65 percent of this total. In 1990, total water demand was projected to be about 175,000 acre-feet by 2010; however, agricultural water demand was expected to account for only 37 percent of the total demand. New and existing land- and water-use data were collected and compiled during 1992-93 to identify present and historical land and water uses. In 1993, preliminary forecasts for total water demand by 2010 ranged from about 127,500 to 329,000 acre-feet. These wide-ranging estimates indicate that forecasts can change with time as factors that affect water demand change and different forecasting methods are used. The forecasts using the MWD_MAIN (Metropolitan Water District of Southern California Municipal and Industrial Needs) water-demand forecasting system yielded the largest estimates of water demand. These forecasts were based on projections of population growth and other socioeconomic variables. Initial forecasts using the MWD_MAIN forecasting system commonly are considered "interim" or preliminary. Available historical and future socioeconomic data required for the forecasting system are limited for this area. Decisions on local water-resources demand management may be made by members of the Antelope Valley Water Group and other interested parties based on this report, other studies, their best judgement, and cumulative knowledge of local conditions. Potential water-resource management actions in the Antelope Valley include (1) increasing artificial ground-water recharge when excess local runoff (or imported water supplies) are available; (2) implementing water-conservation best-management practices; and (3) optimizing ground-water pumpage throughout the basin.

Water-Resources Investigations Report↗
USGS1999

Sources of phosphorus in stormwater and street dirt from two urban residential basins in Madison, Wisconsin, 1994-95

Eutrophication is a common problem for lakes in agricultural and urban areas, such as Lakes Wingra and Mendota in Madison, Wisconsin. This report describes a study to estimate the sources of phosphorus, a major contributor to eutrophication, to Lakes Wingra and Mendota from two small urban residential drainage basins. The Monroe Basin empties into Lake Wingra, and the Harper Basin into Lake Mendota. Phosphorus data were collected from streets, lawns, roofs, driveways, and parking lots (source areas) within these two basins and were used to estimate loads from each area. In addition to the samples collected from these source areas, flow-composite samples were collected at monitoring stations located at the watershed outfalls (storm sewers); discharge and rainfall also were measured. Resulting data were then used to calibrate the Source Loading and Management Model (SLAMM, version 6.3, copyright 1993, Pitt & Vorhees) for conditions in the city of Madison and determine within these basins which of the source areas are contributing the most phosphorus. Water volumes in the calibrated model were calculated to within 23 percent and 24 percent of those measured at the outfalls of each of the basins. These water volumes were applied to the suspended- solids and phosphorus concentrations that were used to calibrate SLAMM for suspended-solids and phosphorus loads. Suspended-solids loads were calculated to be within 4 percent and 17 percent, total-phosphorus loads within 24 percent and 28 percent, and dissolved-phosphorus loads within 9 percent and 10 percent of those measured at the storm-sewer outfall at the Monroe and Harper basins, respectively. Lawns and streets are the largest sources of total and dissolved phosphorus in the basins. Their combined contribution was approximately 80 percent, with lawns contributing more than the streets. Streets were the largest source of suspended solids. Street-dirt samples were collected using industrial vacuum equipment. Leaves in these samples were separated out and the remaining sediment was sieved into >250 mm, 250-63 mm, 63-25 mm, <25 mm size fractions and were analyzed for total phosphorus. Approximately 75 percent of the sediment mass resides in the >250 mm size fractions. Less than 5 percent of the mass can be found in the particle sizes less than 63 mm. The >250 mm size fraction also contributed nearly 50 percent of the total-phosphorus mass and the leaf fraction contributed an additional 30 percent. In each particle size, approximately 25 percent of the total-phosphorus mass is derived from leaves or other vegetation.

Wisconsin↗
USGS1995

Simulation of the water-table altitude in the Biscayne Aquifer, southern Dade County, Florida, water years 1945-89

A digital model of the flow system in the highly permeable surficial Biscayne aquifer of southern Dade County, Florida, was constructed for the purposes of better understanding processes that influence the flow system and of supporting the construction of a subregional model of the transport of brackish water from a flowing artesian well. Problems that needed resolution in this endeavor included the development of methods to represent the influence of flowing surface water in seasonally inundated wetlands and the influence of a network of controlled canals developed in stages during the simulation time period (water years 1945-89). An additional problem was the general lack of natural aquifer boundaries near the boundaries of the study area. The model construction was based on a conceptual description of the Biscayne aquifer developed from the results of previous U.S. Geological Survey investigations. Modifications were made to an existing three-dimensional finite-difference simulator of ground-water flow to enable an upper layer of the grid to represent seasonally occurring overland sheetflow in a series of transient simulations of water levels from 1945 to 1989. A rewetting procedure was developed for the simulator that permitted resaturation of cells in this layer when the wet season recurred. An "equivalent hydraulic conductivity" coefficient was assigned to the overland flow layer that was analogous, subject to various approximations, to the use of the Manning equation. The surficial semiconfining peat and marl layers, levees, canals, and control structures were also represented as part of the model grid with the appropriate choices of hydraulic coefficient values. For most of the Biscayne aquifer grid cells, the value assigned to hydraulic conductivity for model calibration was 30,000 feet per day and the value assigned to porosity was 20 percent. Boundary conditions were specified near data sites having long-term records of surface-water stages or water-table altitudes, and modifications to the simulator permitted the specification of time-varying pressures at boundary grid cells. Rainfall data from a station in Homestead generally were used as an areally uniform rainfall specification throughout the modeled region. Maximum evapotranspiration rates ranged seasonally from a minimum of 0.08 inch per day in January to a maximum of 0.21 inch per day between June and October. Shallow-root and deep-root zone depths for the evapotranspiration calculation were 3 and 20 feet in the coastal ridge and were 0.10 and 5 feet in the glades regions where peat and marl covers occurred. Results of sensitivity analyses indicated that the simulations of stages and water levels were relatively unresponsive to 50 percent changes in aquifer hydraulic conductivity, porosity, and the equivalent hydraulic conductivity of overland flow. However, 20 percent changes in rainfall and maximum evapotranspiration rates produced significantly different water levels, as did interchange of coastal ridge and glades deep-root zone (extinction) depths. Water levels were simulated very well at most measurement sites. Sensitivity analyses illustrated the significant influence of the uncontrolled agricultural drainage canals on pre-1968 regional water levels and the further influence of Black Creek Canal in draining a region of high water after 1961. Other analyses indicated that the flood-control system of 1968-82 lowered peak water levels in the affected region by as much as 1.5 feet in the wet summers of 1968, 1969, and 1981, and that Levee 67 Extended channeled flows from the S-12 spillway structures and raised overland flow stages in Shark River Slough. Hypothetical scenarios of well-field pumping in the vicinity of Levee 31N indicated that the pumping induced a significant amount of recharge from the adjacent borrow canal, the degree of which depended on the distance between the canal and the well field. The computed ratio of evapotranspiration to rainfall recharge ranged from 88 to 94 percent during water years 1945-82. The ratio increased to about 97.9 percent during water years 1983-89, possibly because of changing water-management practices and deficient rainfall.

Florida↗
USGS2008

Factors Affecting Nitrate Delivery to Streams from Shallow Ground Water in the North Carolina Coastal Plain

An analysis of data collected at five flow-path study sites between 1997 and 2006 was performed to identify the factors needed to formulate a comprehensive program, with a focus on nitrogen, for protecting ground water and surface water in the North Carolina Coastal Plain. Water-quality protection in the Coastal Plain requires the identification of factors that affect the transport of nutrients from recharge areas to streams through the shallow ground-water system. Some basins process or retain nitrogen more readily than others, and the factors that affect nitrogen processing and retention were the focus of this investigation to improve nutrient management in Coastal Plain streams and to reduce nutrient loads to coastal waters. Nitrate reduction in ground water was observed at all five flow-path study sites in the North Carolina Coastal Plain, although the extent of reduction at each site was influenced by various environmental, hydrogeologic, and geochemical factors. Denitrification was the most common factor responsible for decreases in nitrate along the ground-water flow paths. Specific factors, some of which affect denitrification rates, that appeared to influence ground-water nitrate concentrations along the flow paths or in the streams include soil drainage, presence or absence of riparian buffers, evapotranspiration, fertilizer use, ground-water recharge rates and residence times, aquifer properties, subsurface tile drainage, sources and amounts of organic matter, and hyporheic processes. The study data indicate that the nitrate-reducing capacity of the buffer zone combined with that of the hyporheic zone can substantially lower the amount of ground-water nitrate discharged to streams in agricultural settings of the North Carolina Coastal Plain. At the watershed scale, the effects of ground-water discharge on surface-water quality appear to be greatly influenced by streamflow conditions and the presence of extensive riparian vegetation. Streamflow statistics that reflect base flow and the general hydrologic dynamics of a stream are important in understanding nutrient transport from a watershed and may be useful indicators of watersheds that are likely to have higher yields of nutrients and water. Combining streamflow statistics with information on such factors as land use, soil drainage, extent of riparian vegetation, geochemical conditions, and subsurface tile drainage in the Coastal Plain can be useful in identifying watersheds that are most likely to export excessive nitrogen due to nonpoint-source loadings and watersheds that are effective in processing nitrogen.

North Carolina↗
USGS1997

Simulation of the water-table altitude in the Biscayne Aquifer, southern Dade County, Florida, water years 1945-89

A digital model of the flow system in the highly permeable surficial Biscayne aquifer of southern Dade County, Florida, was constructed for the purposes of better understanding processes that influence the flow system and of supporting the construction of a subregional model of the transport of brackish water from a flowing artesian well. Problems that needed resolution in this endeavor included the development of methods to represent the influence of flowing surface water in seasonally inundated wetlands and the influence of a network of controlled canals developed in stages during the simulation time period (water years 1945-89). An additional problem was the general lack of natural aquifer boundaries near the boundaries of the study area. The model construction was based on a conceptual description of the Biscayne aquifer developed from the results of previous U.S. Geological Survey investigations. Modifications were made to an existing three-dimensional finite-difference simulator of ground-water flow to enable an upper layer of the grid to represent seasonally occurring overland sheet flow in a series of transient simulations of water levels from 1945 to 1989. A rewetting procedure was developed for the simulator that permitted re-saturation of cells in this layer when the wet season recurred. An �equivalent hydraulic conductivity� coefficient was assigned to the overland flow layer that was analogous, subject to various approximations, to the use of the Manning equation. The surficial semi-confining peat and marl layers, levees, canals, and control structures were also represented as part of the model grid with the appropriate choices of hydraulic coefficient values. For most of the Biscayne aquifer grid cells, the value assigned to hydraulic conductivity for model calibration was 30,000 feet per day and the value assigned to porosity was 20 percent. Boundary conditions were specified near data sites having long-term records of surface-water stages or water-table altitudes, and modifications to the simulator permitted the specification of time-varying pressures at boundary grid cells. Rainfall data from a station in Homestead generally were used as an a really uniform rainfall specification throughout the modeled region. Maximum evapotranspiration rates ranged seasonally from a minimum of 0.08 inch per day in January to a maximum of 0.21 inch per day between June and October. Shallow-root and deep-root zone depths for the evapotranspiration calculation were 3 and 20 feet in the coastal ridge and were 0.10 and 5 feet in the glades regions where peat and marl covers occurred. Results of sensitivity analyses indicated that the simulations of stages and water levels were relatively unresponsive to 50 percent changes in aquifer hydraulic conductivity, porosity, and the equivalent hydraulic conductivity of overland flow. However, 20 percent changes in rainfall and maximum evapotranspiration rates produced significantly different water levels, as did interchange of coastal ridge and glades deep-root zone (extinction) depths. Water levels were simulated very well at most measurement sites. Sensitivity analyses illustrated the significant influence of the uncontrolled agricultural drainage canals on pre-1968 regional water levels and the further influence of Black Creek Canal in draining a region of high water after 1961. Other analyses indicated that the flood-control system of 1968-82 lowered peak water levels in the affected region by as much as 1.5 feet in the wet summers of 1968, 1969, and 1981, and that Levee 67 Extended channeled flows from the S-12 spillway structures and raised overland flow stages in Shark River Slough. Hypothetical scenarios of well-field pumping in the vicinity of Levee 31N indicated that the pumping induced a significant amount of recharge from the adjacent borrow canal, the degree of which depended on the distance between the canal and the well field. The computed ratio of evapotranspiration to rainfall recharge ranged from 88 to 94 percent during water years 1945-82. The ratio increased to about 97.9 percent during water years 1983-89, possibly because of changing water-management practices and deficient rainfall.

Florida↗
USGS2017

Groundwater flow model for the Little Plover River basin in Wisconsin’s Central Sands

The Little Plover River is a groundwater-fed stream in the sand plains region of central Wisconsin. In this region, sandy sediment deposited during or soon after the last glaciation forms an important unconfined sand and gravel aquifer. This aquifer supplies water for numerous high-capacity irrigation, municipal, and industrial wells that support a thriving agricultural industry. In recent years the addition of many new wells, combined with observed diminished flows in the Little Plover and other nearby rivers, has raised concerns about the impacts of the wells on groundwater levels and on water levels and flows in nearby lakes, streams, and wetlands. Diverse stakeholder groups, including well operators, Growers, environmentalists, local land owners, and regulatory and government officials have sought a better understanding of the local groundwater-surface water system and have a shared desire to balance the water needs of the he liagricultural, industrial, and urban users with the maintenance and protection of groundwater-dependent natural resources. To help address these issues, the Wisconsin Department of Natural Resources requested that the Wisconsin Geological and Natural History Survey and U.S. Geological Survey cooperatively develop a groundwater flow model that could be used to demonstrate the relationships among groundwater, surface water, and well withdrawals and also be a tool for testing and evaluating alternative water management strategies for the central sands region. Because of an abundance of previous studies, data availability, local interest, and existing regulatory constraints the model focuses on the Little Plover River watershed, but the modeling methodology developed during this study can apply to much of the larger central sands of Wisconsin. The Little Plover River groundwater flow model simulates three-dimensional groundwater movement in and around the Little Plover River basin under steady-state and transient conditions. This model explicitly includes all high-capacity wells in the model domain and simulates seasonal variations in recharge and well pumping. The model represents the Little Plover River, and other significant streams and drainage ditches in the model domain, as fully connected to the groundwater system, computes stream base flow resulting from groundwater discharge, and routes the flow along the stream channel. A separate soil-water-balance (SWB) model was used to develop groundwater recharge arrays as input for the groundwater flow model. The SWB model uses topography, soils, land use, and climatic data to estimate recharge as deep drainage from the soil zone. The SWB model explicitly includes recharge originating as irrigation water, and computes irrigation using techniques similar to those used by local irrigation operators. The groundwater flow model uses the U.S. Geological Survey’s MODFLOW modeling code which is freely available, widely accepted, and commonly used by the groundwater community. The groundwater flow model and the SWB model use identical high-resolution numerical grids having model cells 100 feet on a side, with physical properties assigned to each grid cell. This grid allows accurate geographic placement of wells, streams, and other model features. The 3-dimensional grid has three layers; layers 1 and 2 represent the sand and gravel aquifer and layer 3 represents the underlying sandstone. The distribution of material properties in the model (hydraulic conductivity, aquifer thickness, etc.) comes from previous published geologic studies of the region, updated by calibration to recent streamflow and groundwater level data. The SWB model operates on a daily time step. The groundwater flow model was calibrated to monthly stress periods with time steps ranging from 1 to 16 days. More detailed time discretization is possible. The groundwater model was calibrated to water-level and streamflow data collected during 2013 and 2014 by adjusting model parameters (primarily hydraulic conductivity, storage, and recharge) until the model produced a conditionally optimal fit between field observations and model output, subject to consistency with previously published geologic studies. Calibration was performed under both steady and transient conditions, and used a sophisticated parameter-estimation procedure (PEST) for the calibration process and to identify important model parameters. For the Little Plover River, the two most important parameters are the global recharge multiplier and the hydraulic conductivity of the stream bed. The calibrated model produces water-level and mass-balance results that are consistent with field observations and previous studies of the area. The completed model is a powerful tool for testing and demonstrating alternative water-management scenarios. Example model applications described in this report include simulating how the cumulative impacts of pumping and land-use change have affected average baseflow in the Little Plover River. Depletion-potential mapping represents a method for predicting which wells and well locations have the greatest impact on nearby surface-water resources. The completed model is publicly available, along with a companion user’s guide to assist with its operation, at http://wgnhs.org/littleplover- river-groundwater-model.

Wisconsin↗
USGS2024

Complex hydrology and variability of nitrogen sources in a karst watershed

Streams draining karst areas with rapid groundwater transit times may respond relatively quickly to nitrogen reduction strategies, but the complex hydrologic network of interconnected sinkholes and springs is challenging for determining the placement and effectiveness of management practices. This study aims to inform nitrogen reduction strategies in a representative agricultural karst setting of the Chesapeake Bay watershed (Fishing Creek watershed, Pennsylvania) with known elevated nitrate contamination and a previous documented groundwater residence time of less than a decade. During baseflow conditions, streamflow did not increase with drainage area. Headwaters and the main stem lost substantial flow to sinkholes until eventually discharging along large springs downstream. Seasonal hydrologic conditions shift the flow and nitrogen load spatially among losing and gaining stream sections. A compilation of nitrogen source inputs with the geochemistry and the pattern of enrichment of δ 15 N and δ 18 O suggest that the nitrogen in streams and springs during baseflow represents a mixture of manure, fertilizer, and wastewater sources with low potential for denitrification. The pH and calcite saturation index increased along generalized flow paths from headwaters to springs and indicate shorter groundwater residence times in baseflow during the spring versus summer. Given the substantial investment in management practices, fixed monitoring sites could incorporate synoptic water sampling to properly monitor long-term progress and help inform management actions in karst watersheds. Although karst watersheds have the potential to respond to nitrogen reduction strategies due to shorter groundwater residence times, high nitrogen inputs, effectiveness of conservation practices, and release of legacy nutrients within the karst cavities could confound progress of water quality goals.

Pennsylvania↗
USGS2021

Tracking the source of metals to the San Juan River

Introduction The San Juan River is a major water source for communities in the Four Corners Region of the United States (Colorado, Arizona, New Mexico, Utah) and is a vital source of water for the Navajo Nation. The Navajo Nation Environmental Protection Agency (NNEPA) periodically samples surface water on the Navajo Nation and has found that some elements exceed NNEPA surface water standards (the upper limits of an element for consumption or other use of water). Constituents of concern are substances that could be harmful if present in sufficient quantities, and it is important to keep track of the concentrations of these substances in the environment. In the San Juan River, constituents of concern include metals detected in river water, such as arsenic, lead, and aluminum. These metals can come from natural sources or can result from human activities (anthropogenic) and can affect the health of people, plants, and animals. The Animas River is one natural source of metals to the San Juan River because of the types of rock through which the Animas River flows and because of hard rock mining at the headwaters. Other potential sources of metals are oil and gas development, coal mining, coal-fired power plants, urban areas, illegal trash dumping, abandoned uranium mines and mills, overgrazed areas, natural geology, and leaching from subsurface agricultural return flows. Determining how much each of these sources contributes and the relative effect of each source on San Juan River water will help the Navajo Nation in their efforts to protect human health and the environment along the San Juan River. The U.S. Geological Survey (USGS) is working with the NNEPA to identify sources of metals and trace elements entering the San Juan River from tributaries in the reach flowing through the Navajo Nation and to quantify the contribution from each natural and human-caused source. The USGS and NNEPA worked with local community members to locate tributaries where sampling equipment was installed. The 3-year source-tracking project, starting in spring 2021, will identify where metals at concentrations above safe surface water standards might be entering the river by evaluating the chemical signatures of water in the major tributaries of the San Juan River. Results will provide valuable information to the Navajo Nation, public drinking-water managers, irrigation districts, other stakeholders, scientists, and the public.

Colorado, Arizona, New Mexico, Utah↗
USGS2003

Simulation of ground-water flow and land subsidence in the Antelope Valley ground-water basin, California

Antelope Valley, California, is a topographically closed basin in the western part of the Mojave Desert, about 50 miles northeast of Los Angeles. The Antelope Valley ground-water basin is about 940 square miles and is separated from the northern part of Antelope Valley by faults and low-lying hills. Prior to 1972, ground water provided more than 90 percent of the total water supply in the valley; since 1972, it has provided between 50 and 90 percent. Most ground-water pumping in the valley occurs in the Antelope Valley ground-water basin, which includes the rapidly growing cities of Lancaster and Palmdale. Ground-water-level declines of more than 200 feet in some parts of the ground-water basin have resulted in an increase in pumping lifts, reduced well efficiency, and land subsidence of more than 6 feet in some areas. Future urban growth and limits on the supply of imported water may continue to increase reliance on ground water. To better understand the ground-water flow system and to develop a tool to aid in effectively managing the water resources, a numerical model of ground-water flow and land subsidence in the Antelope Valley ground-water basin was developed using old and new geohydrologic information. The ground-water flow system consists of three aquifers: the upper, middle, and lower aquifers. The aquifers, which were identified on the basis of the hydrologic properties, age, and depth of the unconsolidated deposits, consist of gravel, sand, silt, and clay alluvial deposits and clay and silty clay lacustrine deposits. Prior to ground-water development in the valley, recharge was primarily the infiltration of runoff from the surrounding mountains. Ground water flowed from the recharge areas to discharge areas around the playas where it discharged either from the aquifer system as evapotranspiration or from springs. Partial barriers to horizontal ground-water flow, such as faults, have been identified in the ground-water basin. Water-level declines owing to ground-water development have eliminated the natural sources of discharge, and pumping for agricultural and urban uses have become the primary source of discharge from the ground-water system. Infiltration of return flows from agricultural irrigation has become an important source of recharge to the aquifer system. The ground-water flow model of the basin was discretized horizontally into a grid of 43 rows and 60 columns of square cells 1 mile on a side, and vertically into three layers representing the upper, middle, and lower aquifers. Faults that were thought to act as horizontal-flow barriers were simulated in the model. The model was calibrated to simulate steady-state conditions, represented by 1915 water levels and transient-state conditions during 1915-95 using water-level and subsidence data. Initial estimates of the aquifer-system properties and stresses were obtained from a previously published numerical model of the Antelope Valley ground-water basin; estimates also were obtained from recently collected hydrologic data and from results of simulations of ground-water flow and land subsidence models of the Edwards Air Force Base area. Some of these initial estimates were modified during model calibration. Ground-water pumpage for agriculture was estimated on the basis of irrigated crop acreage and crop consumptive-use data. Pumpage for public supply, which is metered, was compiled and entered into a database used for this study. Estimated annual pumpage peaked at 395,000 acre-feet (acre-ft) in 1952 and then declined because of declining agricultural production. Recharge from irrigation-return flows was estimated to be 30 percent of agricultural pumpage; the irrigation-return flows were simulated as recharge to the regional water table 10 years following application at land surface. The annual quantity of natural recharge initially was based on estimates from previous studies. During model calibration, natural recharge was reduced from the initial estimate of 40,700 acre-ft per year (acre-ft/yr) to 30,300 acre-ft/yr. Results of the model simulations indicate that ground-water storage declined more than 8.5 million acre-ft from 1915 to 1995. During the period of peak agricultural pumping (1949-53), pumpage averaged 363,000 acre-ft/yr, and 79 percent of the ground water withdrawn came from storage primarily from layer 1 (the upper aquifer). Water released from compaction of the aquitards accounted for about 21,600 acre-ft/yr of the ground water removed from storage. Downward leakage from layer 1 into layer 2 (the middle aquifer) accounted for most (86 percent) of the pumpage from layer 2. For the simulation period 1991-95 (a period representing current conditions when pumpage for public supply exceeded agricultural pumpage), pumpage averaged 81,700 acre-ft/yr, and most of the ground water withdrawn from layer 2 came from downward leakage from layer 1. During this period, ground water removed from storage accounted for 17 percent of the total pumpage and recharge from irrigation return accounted for about 39 percent of the total pumpage. Ground water removed from storage as a result of compaction of aquitards was reduced to about 3,800 acre-ft/yr. The calibrated model was used to simulate the response of the aquifer to future pumping scenarios. Results of the simulation of scenario 1, for which total annual pumpage for 1996-2025 remained at the level specified for 1995, showed that water levels continued to rise (as much as 36 feet) in agricultural areas, continuing the long-term recovery from drawdown caused by historical agricultural pumpage. In the areas where pumping for public supply is concentrated, water levels continued to decline and subsidence continued in the central part of the ground-water basin. Water-level declines were largest (more than 100 feet) in the south-central part of the ground-water basin; most of the public-supply pumpage occurs in this area. As much as 1.9 feet of additional subsidence was simulated in the central part of the ground-water basin from 1996 to 2025. For scenario 2, public-supply pumpage was increased by 3.3 percent annually, and annual agricultural pumpage was increased by 75 percent more than that specified for 1995. Pumpage increases for scenario 2 resulted in significant water-level declines in the southern and northeastern part of the Lancaster subbasin; most pumping for public supply occurs in these areas. Results of this simulation showed that water levels declined more than 150 feet in the south-central part of the ground-water basin and that an additional 5 feet of subsidence was simulated in the central part of the basin.

California↗
USGS2006

Integrating human impacts and ecological integrity into a risk-based protocol for conservation planning

Conservation planning aims to protect biodiversity by sustainng the natural physical, chemical, and biological processes within representative ecosystems. Often data to measure these components are inadequate or unavailable. The impact of human activities on ecosystem processes complicates integrity assessments and might alter ecosystem organization at multiple spatial scales. Freshwater conservation targets, such as populations and communities, are influenced by both intrinsic aquatic properties and the surrounding landscape, and locally collected data might not accurately reflect potential impacts. We suggest that changes in five major biotic drivers—energy sources, physical habitat, flow regime, water quality, and biotic interactions—might be used as surrogates to inform conservation planners of the ecological integrity of freshwater ecosystems. Threats to freshwater systems might be evaluated based on their impact to these drivers to provide an overview of potential risk to conservation targets. We developed a risk-based protocol, the Ecological Risk Index (ERI), to identify watersheds with least/most risk to conservation targets. Our protocol combines risk-based components, specifically the frequency and severity of human-induced stressors, with biotic drivers and mappable land- and water-use data to provide a summary of relative risk to watersheds. We illustrate application of our protocol with a case study of the upper Tennessee River basin, USA. Differences in risk patterns among the major drainages in the basin reflect dominant land uses, such as mining and agriculture. A principal components analysis showed that localized, moderately severe threats accounted for most of the threat composition differences among our watersheds. We also found that the relative importance of threats is sensitive to the spatial grain of the analysis. Our case study demonstrates that the ERI is useful for evaluating the frequency and severity of ecosystemwide risk, which can inform local and regional conservation planning.

Tennessee↗
USGS2007

Identifying biotic integrity and water chemistry relations in nonwadeable rivers of Wisconsin: Toward the development of nutrient criteria

We sampled 41 sites on 34 nonwadeable rivers that represent the types of rivers in Wisconsin, and the kinds and intensities of nutrient and other anthropogenic stressors upon each river type. Sites covered much of United States Environmental Protection Agency national nutrient ecoregions VII-Mostly Glaciated Dairy Region, and VIII-Nutrient Poor, Largely Glaciated upper Midwest. Fish, macroinvertebrates, and three categories of environmental variables including nutrients, other water chemistry, and watershed features were collected using standard protocols. We summarized fish assemblages by index of biotic integrity (IBI) and its 10 component measures, and macroinvertebrates by 2 organic pollution tolerance and 12 proportional richness measures. All biotic and environmental variables represented a wide range of conditions, with biotic measures ranging from poor to excellent status, despite nutrient concentrations being consistently higher than reference concentrations reported for the regions. Regression tree analyses of nutrients on a suite of biotic measures identified breakpoints in total phosphorus (~0.06 mg/l) and total nitrogen (~0.64 mg/l) concentrations at which biotic assemblages were consistently impaired. Redundancy analyses (RDA) were used to identify the most important variables within each of the three environmental variable categories, which were then used to determine the relative influence of each variable category on the biota. Nutrient measures, suspended chlorophyll a, water clarity, and watershed land cover type (forest or row-crop agriculture) were the most important variables and they explained significant amounts of variation within the macroinvertebrate (R 2 = 60.6%) and fish (R 2 = 43.6%) assemblages. The environmental variables selected in the macroinvertebrate model were correlated to such an extent that partial RDA analyses could not attribute variation explained to individual environmental categories, assigning 89% of the explained variation to interactions among the categories. In contrast, partial RDA attributed much of the explained variation to the nutrient (25%) and other water chemistry (38%) categories for the fish model. Our analyses suggest that it would be beneficial to develop criteria based upon a suite of biotic and nutrient variables simultaneously to deem waters as not meeting their designated uses. ?? 2007 Springer Science+Business Media, LLC.

Environmental Management↗
USGS1999

Development of a 14-digit Hydrologic Unit Code Numbering System for South Carolina

A Hydrologic Unit Map showing the cataloging units, watersheds, and subwatersheds of South Carolina has been developed by the U.S. Geological Survey in cooperation with the South Carolina Department of Health and Environmental Control, funded through a U.S. Environmental Protection Agency 319 Grant, and the U.S. Department of Agriculture, Natural Resources Conservation Service. These delineations represent 8-, 11-, and 14-digit Hydrologic Unit Codes, respectively. This map presents information on drainage, hydrography, and hydrologic boundaries of the water-resources regions, subregions, accounting units, cataloging units, watersheds, and subwatersheds. The source maps for the basin delineations are 1:24,000-scale 7.5-minute series topographic maps and the base maps are from 1:100,000-scale Digital Line Graphs; however, the data are published at a scale of 1:500,000. In addition, an electronic version of the data is provided on a compact disc. Of the 1,022 subwatersheds delineated for this project, 1,004 range in size from 3,000 to 40,000 acres (4.69 to 62.5 square miles). Seventeen subwatersheds are smaller than 3,000 acres and one subwatershed, located on St. Helena Island, is larger than 40,000 acres. This map and its associated codes provide a standardized base for use by water-resource managers and planners in locating, storing, retrieving, and exchanging hydrologic data. In addition, the map can be used for cataloging water-data acquisition activities, geographically organizing hydrologic data, and planning and describing water-use and related land-use activities.

South Carolina↗
USGS2001

Water quality and nutrient loading in the Klamath River between Keno, Oregon and Seiad Valley, CA from 1996-1998

A water quality study was performed in the mainstem Klamath River from Keno, Oregon to Seiad Valley, California during 1996 through 1998. Four sites within the study area were continuously monitored using multiparameter recorders. Water quality sampling was also performed at these four locations in 1996 and 1997. Additional water quality sampling sites were added in 1998 for a total of 8 locations between Keno and Seiad. Temperature ranged from near zero &deg;C to >25 &deg;C with cooler temperatures in early spring and fall, and maximum temperatures occurring in july and August of each year. Dissolved oxygen concentration ranged from near zero mg/L to >13 mg/L with highest DO occurring in early spring and fall and lowest DO occurring in mid-summer. Air temperature was generally highly correlated with water temperature with r values ranging from 0.8 to 0.9 during the study period from 1996-1998. Water temperature in the study area exceeded chronic (>16&deg;C) and acute (>22&deg;C) criteria for salmonids during the summer months. Although chronic DO &laquo;7 mg/L) criteria were exceeded throughout most of the study area during the summer, in the free-flowing river below Iron Gate Dam the acute DO &laquo;5.5 mg/L) criteria were not exceeded. Nonpoint source pollution in the form of agricultural return flows, industrial, or sewage effluent entering the stream may have resulted in higher ammonia and total organic nitrogen concentrations at the upstream locations in the Klamath River study area (Keno and J.C. Boyle Powerplant). Nitrification of ammonia and organic nitrogen seemed to result in higher concentrations of nitrate in the downstream Klamath River (Iron Gate Dam). Total phosphorus concentration stayed relatively stable through the reservoirs in the study area, but decreased in the downstream direction between Iron Gate Dam and Seiad. Ortho-phosphorus concentrations increased longitudinally through the reservoirs, then decreased in the downstream direction between Iron Gate Dam and Seiad. An increase in ortho-phosphorus concentration can indicate internal cycling occurring in the reservoirs as well as photosynthesis. On an annual basis total phosphorus loading increased longitudinally from up- to downstream between Keno and Seiad. The increase was statistically significant (p =.03) indicating that the reservoirs in series in the Klamath River study area do not function as a nutrient sink. However, during the summer there was no statistically significant difference in total P loading when Keno, Iron Gate and Seia~ locations were compared, therefore, the reservoirs may act as a nutrient sink seasonally. The Klamath River study locations were generally nitrogen limited, although at Keno, a regUlar change from N limitation to P limitation occurred during the fall of all three years of the study. When the Klamath River annual nutrient loading values are compared to other rivers in the vicinity, the Carson, Truckee, and Long Tom Rivers also appear to be nutrient enriched. The Carson and South Yamhill Rivers seem to be N limited systems and the Wood, Long Tom, Snake and Truckee Rivers seem to be P limited systems. Implementing management strategies for reservoir operations to improve water quality and reduce nutrient concentration or loading in the Klamath River study area to benefit anadromous fisheries may be difficult and expensive. However, improving the thermal regime in spring to benefit YOY salmonids may be possible as is short-term relief in late summer for oversummering species. Decreases in nutrient concentration or loading accomplished through best management practices in the water shed may allow general protection of water resources in the Klamath Basin for future needs.

California, Oregon↗
USGS2023

Colorado River Basin

The Colorado River is often referred to as “the lifeblood of the west.” The basin supplies municipal water to nearly 40 million people and irrigates approximately 22,000 km 2 of agricultural lands. Twenty-two major rivers converge with the Colorado after it begins its descent from the Rocky Mountains and winds through the plateaus of Colorado, Utah, and Arizona, onto the deserts of southwestern Arizona, and finally into the Gulf of California, where inflows from the Río Hardy and Río Sonoyta in Mexico complete the drainage. The mainstem Colorado, Green, Yampa, Little Colorado, and Yampa Rivers are described in further detail in the 2005 edition (Blinn and Poff, 2005) of this book. In this edition, we discuss seven other major tributaries in the Colorado River basin: the Gunnison, San Juan, Virgin, Bill Williams, Verde, Black, and Salt Rivers. The water quality and quantity, flora and fauna, and sediment and organic loads of each of these tributaries uniquely alter the mainstem Colorado River and the habitat it provides. Thus, understanding the hydrology, ecology, and human use of these tributaries is critical toward understanding both the complex history and present-day management of the Colorado River Basin as a whole.

Arizona, Baja California, California, Colorado, Ne↗
USGS2016

Inter-annual variability of area-scaled gaseous carbon emissions from wetland soils in the Liaohe Delta, China

Global management of wetlands to suppress greenhouse gas (GHG) emissions, facilitate carbon (C) sequestration, and reduce atmospheric CO 2 concentrations while simultaneously promoting agricultural gains is paramount. However, studies that relate variability in CO 2 and CH 4 emissions at large spatial scales are limited. We investigated three-year emissions of soil CO 2 and CH 4 from the primary wetland types of the Liaohe Delta, China, by focusing on a total wetland area of 3287 km 2 . One percent is Suaeda salsa , 24% is Phragmites australis , and 75% is rice. While S . salsa wetlands are under somewhat natural tidal influence, P . australis and rice are managed hydrologically for paper and food, respectively. Total C emissions from CO 2 and CH 4 from these wetland soils were 2.9 Tg C/year, ranging from 2.5 to 3.3 Tg C/year depending on the year assessed. Primary emissions were from CO 2 (~98%). Photosynthetic uptake of CO 2 would mitigate most of the soil CO 2 emissions, but CH 4 emissions would persist. Overall, CH 4 fluxes were high when soil temperatures were >18°C and pore water salinity <18 PSU. CH 4 emissions from rice habitat alone in the Liaohe Delta represent 0.2% of CH 4 carbon emissions globally from rice. With such a large area and interannual sensitivity in soil GHG fluxes, management practices in the Delta and similar wetlands around the world have the potential not only to influence local C budgeting, but also to influence global biogeochemical cycling.

Liaohe Delta↗
USGS2009

Recharge rates and chemistry beneath playas of the High Plains aquifer: A literature review and synthesis

Playas are ephemeral, closed-basin wetlands that are important zones of recharge to the High Plains (or Ogallala) aquifer and critical habitat for birds and other wildlife in the otherwise semiarid, shortgrass prairie and agricultural landscape. The ephemeral nature of playas, low regional recharge rates, and a strong reliance on ground water from the High Plains aquifer has prompted many questions regarding the contribution of recharge from playas to the regional aquifer. To address these questions and concerns, the U.S. Geological Survey, in cooperation with the Playa Lakes Joint Venture, present a review and synthesis of the more than 175 publications about recharge rates and chemistry beneath playas and interplaya settings. Although a number of questions remain regarding the controls on recharge rates and chemistry beneath playas, the results from most published studies indicate that recharge rates beneath playas are substantially (1 to 2 orders of magnitude) higher than recharge rates beneath interplaya settings. The synthesis presented here supports the conceptual model that playas are important zones of recharge to the High Plains aquifer and are not strictly evaporative pans. The major findings of this synthesis yield science-based implications for the protection and management of playas and ground-water resources of the High Plains aquifer and directions for future research.

High Plains aquifer↗
USGS1979

Ground-water quality in Bannock, Bear Lake, Caribou, and part of Power counties, southeastern Idaho

This report provides information about the current quality of ground waters in southeastern Idaho and discusses the natural and manmade environmental controls on that quality. This information will be useful in planning and monitoring the development and use of the ground-water resources of southeastern Idaho. The southeastern corner of Idaho, as described in this report, encompasses an area of about 4,000 mil in Bannock, Bear Lake, Caribou, and part of Power Counties. The popu- lation of the area in 1975, based on best estimates by the Idaho Division of Budget, Policy Planning, and Coordination (1976) was 75,200. About 80 percent of the population is in and near the city of Pocatello, which is the second largest population center in the State. Pocatello's economy depends largely on manufacturing and industrial processing, which includes chemicalfertilizer plants. The econ- omy in the rural areas depends largely on agriculture--both dry and irrigated farming are practiced. Mining is important and expected to dominate the economy in the eastcentral part of the area in the future. Natural resources include phosphate ore, which makes up about 35 percent of the U.S. reserves (U.S. Department of Interior and U.S. Department of Agriculture, 1977); ground water, which mostly underlies the several intermontane valleys that dissect the area; and hot springs, which indicate that geothermal energy sources may underlie part of the area. Also, current (1978) speculation is that petroleum reserves may be present in the vicinity of Bear Lake. Development of more sprink- ler-irrigated lands, increases in population, and growth of phosphate mining are expected to place stress on the ground-water resources, both in quality and quantity. The purpose of this report is to present the results of a study whose primary objectives were (1) to provide current waterquality data representative of the water in several different aquifers (water- bearing formations) in the study area, and (2) to relate these data to natural and manmade environmental controls. The wells sampled during this study establish a quasi-network, which could be resampled in the future to document and analyze changes (if any) in ground-water quality. Based on this information, planners and water managers could better understand the causeand-effect relations controlling water quality and could better manage land and water-resource development. The report is designed for ease of reading and presentation. It uses maps, tables, and abbreviated text to describe geology, hydrology, and ground-water quality and how they are interrelated. Some practical ways for improving water quality are discussed for the benefit of individual water users. The field data collected in making the study are contained in the Data Section of this report. The authors gratefully acknowledge the many individual well owners, municipal officials, and private industries that provided well information and allowed access to their properties and collection of water samples. Without their help, this work could not have been done. Water samples were collected at 103 well sites. Waterlevel measurements were made at 98 of these sites during July, August, and September of 1976. This study was made by the U.S. Geological Survey in cooperation with the Idaho Department of Water Resources. A similar study is being made (1978) in north Idaho. Other studies are planned, specifically to obtain ground-water-quality data in areas where land and water-resource development is expected or accelerating.

Idaho↗