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At least 1,423 records · Page 79Linked to original sources
USGS1989

Regression models for estimating urban storm-runoff quality and quantity in the United States

Urban planners and managers need information about the local quantity of precipitation and the quality and quantity of storm runoff if they are to plan adequately for the effects of storm runoff from urban areas. As result of this need, linear regression models were developed for the estimation of storm-runoff loads and volumes from physical, land-use, and climatic characteristics of urban watersheds throughout the United States. Three statistically different regions were delineated, based on mean annual rainfall, to improve linear regression models. One use of these models is to estimate storm-runoff loads and volumes are gaged and ungaged urban watersheds. The most significant explanatory variables in all linear regression models were total storm rainfall and total contributing drainage area. Impervious area, land-use, and mean annual climatic characteristics were also significant explanatory variables in some linear regression models. Models for dissolved solids, total nitrogen, and total ammonia plus organic nitrogen as nitrogen were the most accurate models for most areas, whereas models for suspended solids were the least accurate. The most accurate models were those for the more arid western United States, and the least accurate were those for areas that had large quantities of mean annual rainfall.

Journal of Hydrology↗
USGS2018

Hydrogeologic setting, conceptual groundwater flow system, and hydrologic conditions 1995–2010 in Florida and parts of Georgia, Alabama, and South Carolina

The hydrogeologic setting and groundwater flow system in Florida and parts of Georgia, Alabama, and South Carolina is dominated by the highly transmissive Floridan aquifer system. This principal aquifer is a vital source of freshwater for public and domestic supply, as well as for industrial and agricultural uses throughout the southeastern United States. Population growth, increased tourism, and increased agricultural production have led to increased demand on groundwater from the Floridan aquifer system, particularly since 1950. The response of the Floridan aquifer system to these stresses often poses regional challenges for water-resource management that commonly transcend political or jurisdictional boundaries. To help water-resource managers address these regional challenges, the U.S. Geological Survey (USGS) Water Availability and Use Science Program began assessing groundwater availability of the Floridan aquifer system in 2009. The current conceptual groundwater flow system was developed for the Floridan aquifer system and adjacent systems partly on the basis of previously published USGS Regional Aquifer-System Analysis (RASA) studies, specifically many of the potentiometric maps and the modeling efforts in these studies. The Floridan aquifer system extent was divided into eight hydrogeologically distinct subregional groundwater basins delineated on the basis of the estimated predevelopment (circa 1880s) potentiometric surface: (1) Panhandle, (2) Dougherty Plain-Apalachicola, (3) Thomasville-Tallahassee, (4) Southeast Georgia-Northeast Florida-South South Carolina, (5) Suwannee, (6) West-central Florida, (7) East-central Florida, and (8) South Florida. The use of these subregions allows for a more detailed analysis of the individual basins and the groundwater flow system as a whole. The hydrologic conditions and associated groundwater budget were updated relative to previous RASA studies to include additional data collected since the 1980s and to reflect the entire groundwater flow system, including the surficial, intermediate, and Floridan aquifer systems for a contemporary period (1995–2010). Inflow to the groundwater flow system of 33,700 million gallons per day (Mgal/d) was assumed to be exclusively from net recharge (precipitation minus evapotranspiration and surface runoff). Outflow from the groundwater flow system included spring discharge (7,700 Mgal/d) and groundwater withdrawals (5,200 Mgal/d). Estimates for all components of the groundwater system were not possible because of large uncertainties associated with internal leakage, coastal discharge, and discharge to streams and lakes. A numerical modeling analysis is required to improve this hydrologic budget calculation and to forecast future changes in groundwater levels and aquifer storage caused by groundwater withdrawals, land-use change, and the effects of climate variability and change.

Alabama, Florida, Georgia, South Carolina↗
USGS2000

Geology, hydrology, and ground-water quality of the upper part of the Galena-Platteville aquifer at the Parson's Casket Hardware Superfund site in Belvidere, Illinois

The geology, hydrology, hydraulic properties, and distribution of contaminants in the upper part of the Galena-Platteville aquifer at the Parson's Casket Hardware Superfund site in Belvidere, Illinois, were characterized on the basis of data collected from boreholes by use of packer assemblies, flowmeter logging, and borehole ground-penetrating radar. Four permeable intervals were identified in the upper part of the Galena-Platteville aquifer: (1) a shallow, subhorizontal fracture from 37 to 40 feet below land surface; (2) an inclined fracture from 75 to 85 feet; (3) a shallow, vuggy interval from 90 to 100 feet; and (4) a deep, vuggy interval from about 140 to 180 feet. The calculated horizontal hydraulic conductivity of the two fractured intervals exceeds 50 feet per day and is more than an order of magnitude greater than that of the vuggy intervals. Water levels in the Galena-Platteville aquifer respond to pumping cycles in the Belvidere municipal-supply wells below a depth of at least 180 feet. Results of flowmeter logging and constant discharge aquifer testing indicate that the shallow, subhorizontal fracture is hydraulically connected to the overlying unconsolidated aquifer. Discrete inclined fractures are the primary conduits for vertical ground-water flow between the permeable units within the upper part of the Galena-Platteville aquifer, and perhaps for flow to the deeper parts of the aquifer. The inclined fractures may become less permeable with depth. A maximum effective porosity in the deep, vuggy interval of 8.8 percent was calculated from hydrologic and borehole radar-tomography data collected during tracer testing. The average maximum horizontal ground-water velocity through this interval was calculated at 21.4 feet per day using cross-hole radar tomography under a hydraulic gradient of 1.25 feet per foot. Trichloroethene, trichloroethane, and tetrachloroethene are the primary volatile organic compounds detected in the aquifer. There is no distinct pattern of the concentration of volatile organic compounds with depth; however, the highest concentrations tend to be present in the shallow part of the aquifer at the site. Movement of organic compounds through vertical fractures may account for their presence in the deeper parts of the aquifer.

Illinois↗
USGS2021

Grand challenges of hydrologic modeling for food-energy-water nexus security in high mountain Asia

Climate-influenced changes in hydrology affect water-food-energy security that may impact up to two billion people downstream of the High Mountain Asia (HMA) region. Changes in water supply affect energy, industry, transportation, and ecosystems (agriculture, fisheries) and as a result, also affect the region's social, environmental, and economic fabrics. Sustaining the highly interconnected food-energy-water nexus (FEWN) will be a fundamental and increasing challenge under a changing climate regime. High variability in topography and distribution of glaciated and snow-covered areas in the HMA region, and scarcity of high resolution ( in-situ ) data make it difficult to model and project climate change impacts on individual watersheds. We lack basic understanding of the spatial and temporal variations in climate, surface impurities in snow and ice such as black carbon and dust that alter surface albedo, and glacier mass balance and dynamics. These knowledge gaps create challenges in predicting where and when the impact of changes in river flow will be the most significant economically and ecologically. In response to these challenges, the United States National Aeronautics and Space Administration (NASA) established the High Mountain Asia Team (HiMAT) in 2016 to conduct research to address knowledge gaps. This paper summarizes some of the advances HiMAT made over the past 5 years, highlights the scientific challenges in improving our understanding of the hydrology of the HMA region, and introduces an integrated assessment framework to assess the impacts of climate changes on the FEWN for the HMA region. The framework, developed under a NASA HMA project, links climate models, hydrology, hydropower, fish biology, and economic analysis. The framework could be applied to develop scientific understanding of spatio-temporal variability in water availability and the resultant downstream impacts on the FEWN to support water resource management under a changing climate regime.

Frontiers in Water↗
USGS2012

Interannual variability of snowmelt in the Sierra Nevada and Rocky Mountains, United States: examples from two alpine watersheds

The distribution of snow and the energy flux components of snowmelt are intrinsic characteristics of the alpine water cycle controlling the location of source waters and the effect of climate on streamflow. Interannual variability of these characteristics is relevant to the effect of climate change on alpine hydrology. Our objective is to characterize the interannual variability in the spatial distribution of snow and energy fluxes of snowmelt in watersheds of a maritime setting, Tokopah Basin (TOK) in California's southern Sierra Nevada, and a continental setting, Green Lake 4 Valley (GLV4) in Colorado's Front Range, using a 12 year database (1996–2007) of hydrometeorological observations and satellite-derived snow cover. Snowpacks observed in GLV4 exhibit substantially greater spatial variability than in TOK (0.75 versus 0.28 spatial coefficient of variation). In addition, modeling results indicate that the net turbulent energy flux contribution to snowmelt in GLV4 is, on average, 3 times greater in magnitude (mean 29% versus 10%) and interannual variability (standard deviation 17% versus 6%) than in TOK. These energy flux values exhibit strong seasonality, increasing as the melt season progresses to times later in the year (R 2 = 0.54–0.77). This seasonality of energy flux appears to be associated with snowmelt rates that generally increase with onset date of melt (0.02 cm d -2 ). This seasonality in snowmelt rate, coupled to differences in hydrogeology, may account for the observed differences in correspondence between the timing of snowmelt and timing of streamflow in these watersheds.

Sierra Nevada;Rocky Mountains↗
USGS2006

Hydrology and water quality in the Green River and surrounding agricultural areas near Green River in Emery and Grand Counties, Utah, 2004-05

Water from the Colorado River and its tributaries is used for municipal and industrial purposes by about 27 million people and irrigates nearly 4 million acres of land in the Western United States. Water users in the Upper Colorado River Basin consume water from the Colorado River and its tributaries, reducing the amount of water in the river. In addition, application of water to agricultural land within the basin in excess of crop needs can increase the transport of dissolved solids to the river. As a result, dissolved-solids concentrations in the Colorado River have increased, affecting downstream water users. During 2004-05, the U.S. Geological Survey, in cooperation with the Natural Resources Conservation Service, investigated the occurrence and distribution of dissolved solids in water from the agricultural areas near Green River, Utah, and in the adjacent reach of the Green River, a principle tributary of the Colorado River. The flow-weighted concentration of dissolved solids diverted from the Green River for irrigation during 2004 and 2005 was 357 milligrams per liter and the mean concentration of water collected from seeps and drains where water was returning to the river during low-flow conditions was 4,170 milligrams per liter. The dissolved-solids concentration in water from the shallow part of the ground-water system ranged from 687 to 55,900 milligrams per liter. Measurable amounts of dissolved solids discharging to the Green River are present almost exclusively along the river banks or near the mouths of dry washes that bisect the agricultural areas. The median dissolved-solids load in discharge from the 17 drains and seeps visited during the study was 0.35 ton per day. Seasonal estimates of the dissolved-solids load discharging from the study area ranged from 2,800 tons in the winter to 6,400 tons in the spring. The estimate of dissolved solids discharging from the study area annually is 15,700 tons. Water samples collected from selected sites within the Green River agricultural areas were analyzed for naturally occurring isotopes of strontium and boron, which can be useful for differentiating dissolved-solids sources. Substantial variations in the delta strontium-87 and delta boron-11 values among the sites were measured. Canal and river samples had relatively low concentrations of strontium and the most positive (heavier) isotopic ratios, while drains and seeps had a wide range of strontium concentrations and isotopic ratios that generally were less positive (lighter). Further study of the variation in strontium and boron concentrations and isotope ratios may provide a means to distinguish end members and discern processes affecting dissolved solids within the Green River study area; however, the results from isotope data collected during this study are inconclusive. Flow and seepage losses were estimated for the three main canals in the study area for May 2 to October 4 in any given year. This period coincides with the frost-free period in the Green River area. Estimated diversion from the Green River into the Thayn, East Side, and Green River Canals is 6,600, 6,070, and 19,900 acre-feet, respectively. The estimated seepage loss to ground water from the Thayn, East Side, and Green River Canals during the same period is 1,550, 1,460, and 4,710 acre-feet, respectively.

Utah↗
USGS1977

Ground-water hydrology of the Lower Milliken-Sarco-Tulucay Creeks area, Napa County, California

The Sonoma Volcanics are the principal water-bearing materials in the lower Milliken-Sarco-Tulucay Creeks area, which occupies about 15 square miles (39 square kilometers) in and east of Napa, Calif. The distribution and composition of these volcanic units are highly variable and complex. Within the Sonoma Volcanics the tuffs constitute the best ground-water reservoir. They are principally pumicitic ash-flow tuffs, partly welded and moderately permeable. These tuffs extend to a depth exceeding 500 feet (150 meters), and are irregularly interbedded with clay, igneous flows, and other volcanically derived material of very low permeability which locally confine the tuffs. Recharge and movement of ground water within these tuffs are affected by the highly variable character of this rock sequence, by adjacent formations, and by tectonic features such as the Cup and Saucer ridge and the Soda Creek fault. The lithology of the area limits specific yields to about 4 percent (unconfined conditions). Specific capacities of wells average less than 3 gallons per minute per foot of drawdown (0.6 liter per second per meter) except in the most permeable areas. Annual pumpage of 3,000 acre-feet (3.7 cubic hectometers), mostly from the Sonoma tuffs, represents a significant portion of the ground-water discharge. The seasonal change in ground-water storage was about 6,600 acre-feet (8.1 cubic hectometers) in 1975. Water-level data from the area reflect the seasonal change in ground-water storage, with fluctuations of 3 to 60 feet (1 to 18 meters). The storage capacity to a depth of 500 feet (150 meters) may be as much as 196,000 acre-feet (242 cubic hectometers) in the study area, but physical and economic factors may restrict the usable capacity to about 20,000 acre-feet (25 cubic hectometers). Recharge within the area is generally inadequate to marginal under 1975 demand. There is insufficient recharge in the Milliken and Sarco Creeks area to support 1975 pumpage. Long-term changes in the seasonal peak water levels indicate an average decline of 1.5 feet per year (0.5 meter per year). By 1975 annual pumpage was not exceeding recharge in the Tulucay Creek area. Although a downward trend in water levels was noted in the western part of this basin in the late 1940's, the pumping distribution and its stress on the ground-water system have since changed, and no overall downward trend was evident in the Tulucay Creek area in 1975.

California↗
USGS2001

Post-fire, rainfall intensity-peak discharge relations for three mountainous watersheds in the Western USA

Wildfire alters the hydrologic response of watersheds, including the peak discharges resulting from subsequent rainfall. Improving predictions of the magnitude of flooding that follows wildfire is needed because of the increase in human population at risk in the wildland-urban interface. Because this wildland-urban interface is typically in mountainous terrain, we investigated rainfall-runoff relations by measuring the maximum 30 min rainfall intensity and the unit-area peak discharge (peak discharge divided by the area burned) in three mountainous watersheds (17-26.8 km 2 ) after a wildfire. We found rainfall-runoff relations that relate the unit-area peak discharges to the maximum 30 min rainfall intensities by a power law. These rainfall-runoff relations appear to have a threshold value for the maximum 30 min rainfall intensity (around 10 mm h -1 ) such that, above this threshold, the magnitude of the flood peaks increases more rapidly with increases in intensity. This rainfall intensity could be used to set threshold limits in rain gauges that are part of an early-warning flood system after wildfire. The maximum unit-area peak discharges from these three burned watersheds ranged from 3.2 to 50 m 3 s -1 km -2 . These values could provide initial estimates of the upper limits of runoff that can be used to predict floods after wildfires in mountainous terrain. Published in 2001 by John Wiley and Sons, Ltd.

Hydrological Processes↗
USGS1998

Geographic trend in mercury measured in common loon feathers and blood

The common loon ( Gavia immer ) is a high‐trophic‐level, long‐lived, obligate piscivore at risk from elevated levels of Hg through biomagnification and bioaccumulation. From 1991 to 1996 feather ( n = 455) and blood ( n = 381) samples from adult loons were collected between June and September in five regions of North America: Alaska, northwestern United States, Upper Great Lakes, New England, and the Canadian Maritimes. Concentrations of Hg in adults ranged from 2.8 to 36.7 μg/g (fresh weight) in feathers and from 0.12 to 7.80 μg/g (wet weight) in whole blood. Blood Hg concentrations in 3 to 6‐week‐old juveniles ranged from 0.03 to 0.78 μg/g (wet weight) ( n = 183). To better interpret exposure data, relationships between blood and feather Hg concentrations were examined among age and sex classes. Blood and feather Hg concentrations from the same individuals were significantly correlated and varied geographically ( r 2 ranged from 0.03 to 0.48). Blood and feather Hg correlated strongest in areas with the highest blood Hg levels, indicating a possible carryover of breeding season Hg that is depurated during winter remigial molt. Mean blood and feather Hg concentrations in males were significantly higher than concentrations in females for each region. The mean blood Hg concentration in adults was 10 times higher than that in juveniles, and feather Hg concentrations significantly increased over 1 to 4‐year periods in recaptured individuals. Geographic stratification indicates a significant increasing regional trend in adult and juvenile blood Hg concentrations from west to east. This gradient resembles U.S. Environmental Protection Agency‐modeled predictions of total anthropogenic Hg deposition across the United States. This gradient is clearest across regions. Within‐region blood Hg concentrations in adults and juveniles across nine sites of one region, the Upper Great Lakes, were less influenced by variations in geographic Hg deposition than by hydrology and lake chemistry. Loons breeding on low‐pH lakes in the Upper Great Lakes and in all lake types of northeastern North America are most at risk from Hg.

Alaska, Maine, Michigan, Minnesota, Montana, New B↗
USGS2019

Integration of eDNA-based biological monitoring within the US Geological Survey’s national streamgage network

This study explores the feasibility and utility of integrating environmental DNA (eDNA) assessments of species occurrences into the United States (U.S.) Geological Survey’s national streamgage network. We used an existing network of five gages in southwest Idaho to explore the type of information that could be gained as well as the associated costs and limitations. Hydrologic technicians were trained in eDNA sampling protocols and they collected samples during routine monthly visits to streamgages over an entire water year (2016). We analyzed the eDNA in the filtered water samples to determine the presence of two fish species: bull trout and rainbow trout. We then modeled the spatiotemporal distribution of each species using discharge and temperature data. To assess the influence of the spatial distribution of the gages on the biological information obtained, we also collected eDNA samples from locations between the gages three times during the water year. We found eDNA monitoring at the five gages provided meaningful information about the distribution of both species, especially when detection probabilities accounted for variations in temperature and discharge. Sampling between the gages provided additional information about bull trout distribution — the rarer of the two species. Our study suggests the integration of eDNA sampling into a streamgage network is feasible and could provide a novel and powerful source of biological information for riverine ecosystems in the U.S.

Idaho, Nebraska↗
USGS2000

Ground-penetrating radar methods used in surface-water discharge measurements

The U.S. Geological Survey (USGS) operates a network of about 7,000 streamflow-gaging stations that monitor open-channel water discharge at locations throughout the United States. The expense, technical difficulties, and concern for the safety of operational personnel under some field conditions have led to the search for alternate measurement methods. Ground- penetrating radar (GPR) has been used by the USGS in hydrologic, geologic, environmental, and bridge-scour studies by floating antennas on water or mounting antennas in boats. GPR methods were developed to measure and monitor remotely the cross-sectional area of rivers by suspending a 100-megahertz (MHz) radar antenna from a cableway car or bridge at four unstable streams that drained the slopes of Mount St. Helens in Washington. Based on the success of these initial efforts, an experiment was conducted in 1999 to see if a combination of complementary radar methods could be used to calculate the discharge of a river without having any of the measuring equipment in the water. The cross-sectional area of the 183- meter (m) wide Skagit River in Washington State was measured using a GPR system with a single 100-MHz antenna suspended 0.5 to 3 m above the water surface from a cableway car. A van- mounted, side-looking pulsed-Doppler (10 gigahertz) radar system was used to collect water-surface velocity data across the same section of the river. The combined radar data sets were used to calculate the river discharge and the results compared closely to the discharge measurement made by using the standard in-water measurement techniques. The depth to the river bottom, which was determined from the GPR data by using a radar velocity of 0.04 meters per nanosecond in water, was about 3 m, which was within 0.25 m of the manually measured values.

Washington↗
USGS1982

Volcano-tectonic history of Crater Flat, southwestern Nevada, as suggested by new evidence from drill hole USW-VH-1 and vicinity

New evidence for a possible resurgent dome in the caldera related to eruption of the Bullfrog Member of the Crater Flat Tuff has been provided by recent drilling of a 762-meter (2,501-foot) hole in central Crater Flat. Although no new volcanic units were penetrated by the drill hole (USW-VH-1), the positive aeromagnetic anomaly in the vicinity of the drill hole appears to result in part from the unusually thick, densely welded tuff of the Bullfrog. Major units penetrated include alluvium, basalt of Crater Flat, Tiva Canyon and Topopah Spring Members of the Paintbrush Tuff, and Prow Pass and Bullfrog Members of the Crater Flat Tuff. In addition, the drill hole provided the first subsurface hydrologic information for the area. The water table in the hole is at about 180 meters (600 feet), and the temperature gradient appears slightly higher than normal for the region.

Nevada↗
USGS2010

Water resources of Monroe County, New York, water years 2003-08: Streamflow, constituent loads, and trends in water quality

This report, the sixth in a series published since 1994, presents analyses of hydrologic data in Monroe County for the period October 2002 through September 2008. Streamflows and water quality were monitored at nine sites by the Monroe County Department of Health and the U.S. Geological Survey. Streamflow yields (flow per unit area) were highest in Northrup Creek, which had sustained flows from year-round inflow from the village of Spencerport wastewater-treatment plant and seasonal releases from the New York State Erie (Barge) Canal. Genesee River streamflow yields also were high, at least in part, as a result of higher rainfall and lower evapotranspiration rates in the upper part of the Genesee River Basin than in the other study basins. The lowest streamflow yields were measured in Honeoye Creek, which reflected a decrease in flows due to the withdrawals from Hemlock and Canadice Lakes for the city of Rochester water supply. Water samples collected at nine monitoring sites were analyzed for nutrients, chloride, sulfate, and total suspended solids. The loads of constituents, which were computed from the concentration data and the daily flows recorded at each of the monitoring sites, are estimates of the mass of the constituents that was transported in the streamflow. Annual yields (loads per unit area) also were computed to assess differences in constituent transport among the study basins. All urban sites - Allen Creek and the two downstream sites on Irondequoit Creek - had seasonally high concentrations and annual yields of chloride. Chloride loads are attributed to the application of road-deicing salts to the county's roadways and are related to population and road densities. The less-urbanized sites in the study - Genesee River, Honeoye Creek, and Oatka Creek - had relatively low concentrations and yields of chloride. The highest concentrations and yields of sulfate were measured in Black Creek, Oatka Creek, and Irondequoit Creek at Railroad Mills and are attributable to dissolution of sulfate from gypsum (calcium sulfate) deposits in Silurian shale bedrock that crops out upstream from these monitoring sites. Northrup Creek had the highest concentrations of phosphorus, orthophosphate, and nitrogen, and high yields of nitrate plus nitrite nitrogen and ammonia plus organic nitrogen. These results are attributed to discharges from the Spencerport wastewater-treatment plant (which ceased operation in June 2008), diversions from the New York State Erie (Barge) Canal, and manure and fertilizers applied to agricultural fields. Concentrations and yields of nitrate plus nitrite nitrogen also were high in Oatka Creek and Black Creek; basins with substantial agricultural land uses. Allen Creek had the second highest yield of ammonia plus organic nitrogen. Honeoye Creek, which drains a relatively undeveloped basin, had the lowest yields of nitrogen constituents. The second highest median concentrations and highest sample concentrations of phosphorus and orthophosphate, as well as the highest phosphorus yields, were measured in the Genesee River. A comparison of the yields computed for the two downstream sites on Irondequoit Creek - above Blossom Road and at Empire Boulevard - permitted an assessment of the mitigative effects of the Ellison Park wetland on constituent loads, which would otherwise be transported to Irondequoit Bay. These effects also include those provided by a flow-control structure (installed mid-way through the wetland during February 1997), which was designed to increase the dispersal and short-term detention of stormflows in the wetland. The wetland decreased yields of particulate constituents - phosphorus and ammonia plus organic nitrogen - but had little effect on the yields of dissolved constituents - chloride, sulfate, and nitrate plus nitrite nitrogen. Trends in flow-adjusted concentrations were identified at all sites for most of the nutrient constituents that were evaluated. All of the linear time tren

Scientific Investigations Report↗
USGS1986

Hydrology of carbonate aquifers in southwestern Linn County and adjacent parts of Benton, Iowa, and Johnson Counties, Iowa

Groundwater is the major source of water in Linn County and the surrounding area. Approximately 90 percent of the groundwater production is from Silurian, Devonian, and Quaternary aquifers. The Silurian and Devonian aquifers consist of limestone and dolomite with minor shale beds, which have a regional dip to the southwest of approximately 20 feet per mile. The Silurian aquifer in east-central Iowa is confined from below by Upper Ordovician, Maquoketa Formation shales, and from above by the Kenwood Member of the Wapsipinicon Formation and the Otis and Bertram formations. The Quaternary aquifer consists of unconsolidated sand and gravel beds in the glacial drift, and in the alluvium which is associated with modern streams. The alluvium consists of lenticular beds of poorly-to well-sorted silt, sand, and gravel. The sand and gravel beds are interlayered with relatively-impermeable beds of till, silt, and clay. Water moves through the Silurian aquifer in part due to a complex distribution of porous and dense carbonate facies. Horizons containing skeletal molds in the Silurian dolomite have porosities as much as 39 percent, and are laterally equivalent to dolomites with porosities as little as less than one percent. Because of subsequent fracturing and solutional enlargement of these porous horizons, hydrologic correlation of the primary water-yielding zones is not always possible. One horizon, however, does occur approximately 70 to 105 feet above the base of the Silurian, and is the most consistently productive water-yielding unit in the area. This horizon is Informally referred to as the Farmers Creek aquifer. The potentiometric surface of the Silurian aquifer has a gradient towards the Cedar River, indicating discharge from the aquifer through the alluvium into the river. By comparison, the potentiometric surface of the overlying Devonian aquifer is equal to that of the Silurian and may range to more than 40 feet higher. Yields to individual wells completed in the Silurian and Devonian carbonate aquifers vary from less than 10 to about 500 gallons per minute. Individual wells completed in the Quaternary aquifer yield as much as 2,000 gallons per minute. Water analyses from the Devonian and Silurian aquifers indicate that they are of similar chemical quality at most locations in the study area. However, they may commonly contain concentrations of sulfate that exceed 1,000 mil grams per liter. Dissolved-solids concentrations as much as 2,350 milligrams per liter occur in the Silurian aquifer in the western and southwestern part of the study area. Water from the Quaternary aquifer generally is suitable for most uses and dissolved-solids concentrations generally are less than 750 milligrams per liter.

Iowa↗
USGS2009

Floods of Selected Streams in Arkansas, Spring 2008

Floods can cause loss of life and extensive destruction to property. Monitoring floods and understanding the reasons for their occurrence are the responsibility of many Federal agencies. The National Weather Service, the U.S. Army Corps of Engineers, and the U.S. Geological Survey are among the most visible of these agencies. Together, these three agencies collect and analyze floodflow information to better understand the variety of mechanisms that cause floods, and how the characteristics and frequencies of floods vary with time and location. The U.S. Geological Survey (USGS) has monitored and assessed the quantity of streamflow in our Nation's streams since the agency's inception in 1879. Because of ongoing collection and assessment of streamflow data, the USGS can provide information about a range of surface-water issues including the suitability of water for public supply and irrigation and the effects of agriculture and urbanization on streamflow. As part of its streamflow-data collection activities, the USGS measured streamflow in multiple streams during extreme flood events in Arkansas in the spring of 2008. The analysis of streamflow information collected during flood events such as these provides a scientific basis for decision making related to resource management and restoration. Additionally, this information can be used by water-resource managers to better define flood-hazard areas and to design bridges, culverts, dams, levees, and other structures. Water levels (stage) and streamflow (discharge) currently are being monitored in near real-time at approximately 150 locations in Arkansas. The streamflow-gaging stations measure and record hydrologic data at 15-minute or hourly intervals; the data then are transmitted through satellites to the USGS database and displayed on the internet every 1 to 4 hours. Streamflow-gaging stations in Arkansas are part of a network of over 7,500 active streamflow-gaging stations operated by the USGS throughout the United States in cooperation with other Federal, State, and local government agencies. In Arkansas, the major supporters of the streamflow-gaging network are the U.S. Army Corps of Engineers, Arkansas Natural Resources Commission, Arkansas Department of Environmental Quality, and Arkansas Geological Survey. Many other Federal, State, and local government entities provide additional support for streamflow-gaging stations. It is the combined support of the USGS and all funding partners that make it possible to maintain an adequate streamflow-gaging network in Arkansas. Data collected over the years at streamflow-gaging stations can be used to characterize the relative magnitude of flood events and their statistical frequency of occurrence. These analyses provide water-resource managers with accurate and reliable hydrologic information based on present and historical flow conditions. Continued collection of streamflow data, with consideration of changes in land use, agricultural practices, and climate change, will help scientists to more accurately characterize the magnitude of extreme floods in the future.

Fact Sheet↗
USGS2006

Simulated Effects of Seasonal Ground-Water Pumpage for Irrigation on Hydrologic Conditions in the Lower Apalachicola-Chattahoochee-Flint River Basin, Southwestern Georgia and Parts of Alabama and Florida, 1999-2002

To determine the effects of seasonal ground-water pumpage for irrigation, a finite-element ground-water flow model was developed for the Upper Floridan aquifer in the lower Flint River Basin area, including adjacent parts of the Chattahoochee and Apalachicola River Basins. The model simulates withdrawal from the aquifer at 3,280 irrigation, municipal, and industrial wells; stream-aquifer flow between the aquifer and 36 area streams; leakage to and from the overlying upper semiconfining unit; regional ground-water flow at the lateral boundaries of the model; and water-table recharge in areas where the aquifer is at or near land surface. Steady-state calibration to drought conditions of October 1999 indicated that the model could adequately simulate measured groundwater levels at 275 well locations and streamflow gains and losses along 53 reaches of area streams. A transient simulation having 12 monthly stress periods from March 2001 to February 2002 incorporated time-varying stress from irrigation pumpage, stream and lake stage, head in the overlying upper semiconfining unit, and infiltration rates. Analysis of simulated water budgets of the Upper Floridan aquifer provides estimates of the source of water pumped for irrigation. During October 1999, an estimated 127 million gallons per day (Mgal/d) of irrigation pumpage from the Upper Floridan aquifer in the model area were simulated to be derived from changes in: stream-aquifer flux (about 56 Mgal/d, or 44 percent); leakage to or from the upper semiconfining unit (about 49 Mgal/d, or 39 percent); regional flow (about 18 Mgal/d, or 14 percent); leakage to or from Lakes Seminole and Blackshear (about 2.7 Mgal/d, or 2 percent); and flux at the Upper Floridan aquifer updip boundary (about 1.8 Mgal/d, or 1 percent). During the 2001 growing season (May-August), estimated irrigation pumpage ranged from about 310 to 830 Mgal/ d, about 79 percent of the 12-month total. During the growing season, irrigation pumpage was derived from decreased discharge or increased recharge of stream-aquifer flux (from about 23 to 39 percent), leakage to or from the upper semiconfining unit (from about 30 to 36 percent), regional flow (from about 8 to 11 percent), Lakes Seminole and Blackshear (about 2 percent), and flux at the Upper Floridan aquifer updip boundary (about 1 percent). Storage effects (decreased storage gain or increased storage loss) contributed from about 11 to 36 percent of irrigation pumpage during the growing season. Water managers can use the model to determine where and how much additional ground-water pumpage for irrigation should be permitted based on a variety of hydrologic constraints. For example, the model results may indicate that in some critical locations, additional ground-water pumpage during a prolonged drought might reduce stream-aquifer flux enough to cause noncompliance of established minimum instream flow conditions.

Alabama, Florida, Georgia↗
USGS2010

Surficial geologic map of the Amboy 30' x 60' quadrangle, San Bernardino County, California

The surficial geologic map of the Amboy 30' x 60' quadrangle presents characteristics of surficial materials for an area of approximately 5,000 km2 in the eastern Mojave Desert of southern California. This map consists of new surficial mapping conducted between 2000 and 2007, as well as compilations from previous surficial mapping. Surficial geologic units are mapped and described based on depositional process and age categories that reflect the mode of deposition, pedogenic effects following deposition, and, where appropriate, the lithologic nature of the material. Many physical properties were noted and measured during the geologic mapping. This information was used to classify surficial deposits and to understand their ecological importance. We focus on physical properties that drive hydrologic, biologic, and physical processes such as particle-size distribution (PSD) and bulk density. The database contains point data representing locations of samples for both laboratory determined physical properties and semiquantitative field-based information in the database. We include the locations of all field observations and note the type of information collected in the field to help assist in assessing the quality of the mapping. The publication is separated into three parts: documentation, spatial data, and printable map graphics of the database. Documentation includes this pamphlet, which provides a discussion of the surficial geology and units and the map. Spatial data are distributed as ArcGIS Geodatabase in Microsoft Access format and are accompanied by a readme file, which describes the database contents, and FGDC metadata for the spatial map information. Map graphics files are distributed as Postscript and Adobe Portable Document Format (PDF) files that provide a view of the spatial database at the mapped scale.

Scientific Investigations Map↗
USGS2010

Surficial geologic map of the Amboy 30' x 60' quadrangle, San Bernardino County, California

The surficial geologic map of the Amboy 30' x 60' quadrangle presents characteristics of surficial materials for an area of approximately 5,000 km 2 in the eastern Mojave Desert of southern California. This map consists of new surficial mapping conducted between 2000 and 2007, as well as compilations from previous surficial mapping. Surficial geologic units are mapped and described based on depositional process and age categories that reflect the mode of deposition, pedogenic effects following deposition, and, where appropriate, the lithologic nature of the material. Many physical properties were noted and measured during the geologic mapping. This information was used to classify surficial deposits and to understand their ecological importance. We focus on physical properties that drive hydrologic, biologic, and physical processes such as particle-size distribution (PSD) and bulk density. The database contains point data representing locations of samples for both laboratory determined physical properties and semiquantitative field-based information in the database. We include the locations of all field observations and note the type of information collected in the field to help assist in assessing the quality of the mapping. The publication is separated into three parts: documentation, spatial data, and printable map graphics of the database. Documentation includes this pamphlet, which provides a discussion of the surficial geology and units and the map. Spatial data are distributed as ArcGIS Geodatabase in Microsoft Access format and are accompanied by a readme file, which describes the database contents, and FGDC metadata for the spatial map information. Map graphics files are distributed as Postscript and Adobe Portable Document Format (PDF) files that provide a view of the spatial database at the mapped scale.

California↗