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At least 1,351 records · Page 75Linked to original sources
USGS2008

Ground-Water Flow in the Vicinity of the Ho-Chunk Nation Communities of Indian Mission and Sand Pillow, Jackson County, Wisconsin

An analytic element ground-water-flow model was constructed to help understand the ground-water-flow system in the vicinity of the Ho-Chunk Nation communities of Indian Mission and Sand Pillow in Jackson County, Wisconsin. Data from interpretive reports, well-drillers' construction reports, and an exploratory augering program in 2003 indicate that sand and gravel of varying thickness (0-150 feet[ft]) and porous sandstone make up a composite aquifer that overlies Precambrian crystalline rock. The geometric mean values for horizontal hydraulic conductivity were estimated from specific-capacity data to be 61.3 feet per day (ft/d) for sand and gravel, 6.6 ft/d for sandstone, and 12.0 ft/d for the composite aquifer. A ground-water flow model was constructed, the near field of which encompassed the Levis and Morrison Creeks Watershed. The flow model was coupled to the parameter-estimation program UCODE to obtain a best fit between simulated and measured values of ground-water levels and estimated Q50 flow duration (base flow). Calibration of the model with UCODE provided a ground-water recharge rate of 9 inches per year and a horizontal hydraulic conductivity of 13 ft/d for the composite aquifer. Using these calibrated parameter values, simulated heads from the model were on average within 5 ft of the measured water levels. In addition, these parameter values provided an acceptable base-flow calibration for Hay, Dickey, and Levis Creeks; the calibration was particularly close for Levis Creek, which was the most frequently measured stream in the study area. The calibrated model was used to simulate ground-water levels and to determine the direction of ground-water flow in the vicinity of Indian Mission and Sand Pillow communities. Backward particle tracking was conducted for Sand Pillow production wells under two pumping simulations to determine their 20-year contributing areas. In the first simulation, new production wells 6, 7, and 8 were each pumped at 50 gallons per minute (gal/min). In the second simulation, new production wells 6, 7, and 8 and existing production well 5 were each pumped at 50 gal/min. The second simulation demonstrated interference between the existing production well 5 and the new production wells when all were pumping at 50 gal/min.

Scientific Investigations Report↗
USGS2001

Ground-water quality in the southeastern Sacramento Valley aquifer, California, 1996

In 1996, the U.S. Geological Survey sampled 29 domestic wells and 2 monitoring wells in the southeastern Sacramento Valley as part of the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program. This area, designated as the NAWQA Sacramento subunit study area, was chosen because it had the largest amount of ground-water use in the Sacramento River Basin. The Sacramento subunit study area is about 4,400 square kilometers and includes intense agricultural and urban development. The wells sampled ranged from 14.9 to 79.2 meters deep. Ground-water samples from 31 wells were analyzed for 6 field measurements, 14 inorganic constituents, 6 nutrient constituents, organic carbon, 86 pesticides, 87 volatile organic compounds, tritium (hydrogen-3), radon-222, deuterium (hydrogen-2), and oxygen-18. Nitrate levels were lower than the 2000 drinking-water standards in all but one well, but many detections were in the range that indicated an effect by human activities on ground-water quality. Radon was detected in all wells, and was measured at levels above the proposed Federal 2000 maximum contaminant level in 90 percent of the wells. Five pesticides and one pesticide degradation product were detected in ground-water samples and concentrations were below 2000 drinking-water standards. All pesticides detected during this study have been used in the Sacramento Valley. Thirteen volatile organic compounds were detected in ground water. One detection of trichloroethene was above Federal 2000 drinking-water standards, and another, tetrachloromethane, was above California 1997 drinking-water standards; both occurred in a well that had eight volatile organic compound detections and is near a known source of ground-water contamination. Pesticides and volatile organic compounds were detected in agricultural and urban areas; both pesticides and volatile organic compounds were detected at a higher frequency in urban wells. Ground-water chemistry indicates that natural processes and human activities are affecting ground-water quality in the upper part of the southeastern Sacramento Valley aquifer. The factors identified as having an influence on ground-water quality were redox condition in the aquifer, depth within the aquifer, and land use overlying the aquifer. Nitrate concentra-tions showed a statistical correlation with each of these factors. Detections of pesticides and volatile organic compounds were too few to compare concentrations with the various factors, but the types of synthetic compounds detected were consistent with the sur-rounding land use. Sixty-one percent of the wells sampled in this study showed the effect of human activities on ground-water quality in the form of a nitrate concentration over 3 milligrams per liter or a detection of a pesticide or volatile organic compound. In general, the water quality in the southeastern Sacramento Valley aquifer was found suitable for most uses.

Water-Resources Investigations Report↗
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

Ground-water resources of Catron County, New Mexico

This report describes the occurrence, availability, and quality of ground-water and related surface-water resources in Catron County, the largest county in New Mexico. The county is located in the Lower Colorado River Basin and the Rio Grande Basin, and the Continental Divide is the boundary between the two river basins. Increases in water used for mining activities (coal, mineral, and geothermal), irrigated agriculture, reservoir construction, or domestic purposes could affect the quantity or quality of ground- water and surface-water resources in the county. Parts of seven major drainage basins are within the two regional river basins in the county--Carrizo Wash, North Plains, Rio Salado, San Agustin, Alamosa Creek, Gila, and San Francisco Basins. The San Francisco, Gila, and Tularosa Rivers typically flow perennially. During periods of low flow, most streamflow is derived from baseflow. The stream channels of the Rio Salado and Carrizo Wash Basins are commonly perennial in their upper reaches and ephemeral in their lower reaches. Largo Creek in the Carrizo Wash Basin is perennial downstream from Quemado Lake and ephemeral in the lower reaches. Aquifers in Catron County include Quaternary alluvium and bolson fill; Quaternary to Tertiary Gila Conglomerate; Tertiary Bearwallow Mountain Andesite, Datil Group, and Baca Formation; Cretaceous Mesaverde Group, Crevasse Canyon Formation, Gallup Sandstone, Mancos Shale, and Dakota Sandstone; Triassic Chinle Formation; and undifferentiated rocks of Permian age. Water in the aquifers in the county generally is unconfined; however, confined conditions may exist where the aquifers are overlain by other units of lower permeability. Yields of ground water from the Quaternary alluvium in the county range from 1 to 375 gallons per minute. Yields of ground water from the alluvium in the Carrizo Wash Basin are as much as 250 gallons per minute for short time periods. North of the Plains of San Agustin, ground-water yields from the alluvium in the San Agustin Basin range from 1 to 10 gallons per minute. Irrigation wells completed in the Quaternary bolson fill produce as much as 975 gallons per minute immediately east of the county. Water from the bolson fill in the Plains of San Agustin has specific-conductance values generally ranging from 180 to 3,300 microsiemens per centimeter at 25 degrees Celsius (microsiemens/cm). Yields from the Gila Conglomerate generally range from 2 to 5 gallons per minute. Water samples from two springs from the Gila Conglomerate have specific conductances of 289 and 381 microsiemens/cm. The Tertiary Datil Group is present in the Carrizo Wash, San Agustin, San Francisco, and Gila Basins. The Datil Group commonly is unconfined, but may be confined at depth. Water levels of wells completed in this unit range from 60 to 1,260 feet below land surface. Wells completed in the Datil Group typically yield 1 to 15 gallons per minute. Specific conductance of water from the Datil Group ranges from 210 to 820 microsiemens/cm. The Tertiary Baca Formation in the Carrizo Wash Basin produces 5 to 20 gallons per minute in stock wells. Water from wells completed in the Baca Formation has specific-conductance values ranging from 312 to 752 microsiemens/cm. Aquifers in Cretaceous rocks are present in the Carrizo Wash, North Plains, and Rio Salado Basins. The potential yield from wells completed in Cretaceous rocks in northwestern Catron County is from 1 to 122 gallons per minute. Specific conductance of water from Cretaceous rocks ranges from 210 microsiemens/cm in the Moreno Hill Formation to 4,490 microsiemens/cm in the Mancos Shale. Yields of ground water from Cretaceous rocks in the Carrizo Wash Basin typically range from 1 to 100 gallons per minute; in an artesian well, however, the yield in the main body of the Creta

Water-Resources Investigations Report↗
USGS1979

Digital-transport model study of Diisopropylmethylphosphonate (DIMP) ground-water contamination at the Rocky Mountain Arsenal, Colorado

Diisopropylmethylphosphonate (DIMP) is an organic compound produced as a byproduct of the manufacture and detoxification of GB nerve gas. Ground-water contamination by DIMP from the disposal of wastes into unlined surface ponds at the Rocky Mountain Arsenal occurred from 1952 to 1956. A digital-transport model was used to determine the effects on ground-water movement and on DIMP concentrations in the ground water of a bentonite barrier in the aquifer near the northern boundary of the arsenal. The transport model is based on an iterative-alternating- direction-implicit mathematical solution of the ground-water-flow equation coupled with a method-of-characteristics solution of the solute-transport equation. The model assumes conservative (nonreactive) transient transport of DIMP and steady-state ground-water flow. In the model simulations, a bentonite barrier was assumed that was impermeable and penetrated the entire saturated thickness of the aquifer. Ground water intercepted by the barrier was assumed to be pumped by wells located south (upgra-dient) of the barrier, to be treated to remove DIMP, and to be recharged by pits or wells to the aquifer north (downgradient) of the barrier. The amount of DIMP transported across the northern boundary of the arsenal was substantially reduced by a ground-water-barrier system of this type. For a 1,500-foot-long bentonite barrier located along the northern boundary of the arsenal near D Street, about 50 percent of the DIMP that would otherwise cross the boundary would be intercepted by the barrier. This barrier configuration and location were proposed by the U.S. Army. Of the ground water with DIMP concentrations greater than 500 micro- grams per liter, the safe DIMP-concentration level determined by the U.S. Army, about 72 percent would be intercepted by the barrier system. The amount of DIMP underflow intercepted may be increased to 65 percent by doubling the pumpage, or to 73 percent by doubling the length of the barrier.

Colorado↗
USGS2003

Aquifer tests and simulation of ground-water flow in Triassic sedimentary rocks near Colmar, Bucks and Montgomery Counties, Pennsylvania

This report presents the results of a study by the U.S. Geological Survey in cooperation with the U.S. Environmental Protection Agency to evaluate ground-water flow in Triassic sedimentary rocks near Colmar, in Bucks and Montgomery Counties, Pa. The study was conducted to help the U.S. Environmental Protection Agency evaluate remediation alternatives at the North Penn Area 5 Superfund Site near Colmar, where ground water has been contaminated by volatile organic solvents (primarily trichloroethene). The investigation focused on determining the (1) drawdown caused by separately pumping North PennWater Authority wells NP–21 and NP–87, (2) probable paths of groundwater movement under present-day (2000) conditions (with NP–21 discontinued), and (3) areas contributing recharge to wells if pumping from wells NP-21 or NP–87 were restarted and new recovery wells were installed. Drawdown was calculated from water levels measured in observation wells during aquifer tests of NP–21 and NP–87. The direction of ground-water flow was estimated by use of a three-dimensional ground-water-flow model. Aquifer tests were conducted by pumping NP–21 for about 7 days at 257 gallons per minute in June 2000 and NP–87 for 3 days at 402 gallons per minute in May 2002. Drawdown was measured in 45 observation wells during the NP–21 test and 35 observation wells during the NP–87 test. Drawdown in observation wells ranged from 0 to 6.8 feet at the end of the NP–21 test and 0.5 to 12 feet at the end of the NP–87 test. The aquifer tests showed that ground-water levels declined mostly in observation wells that were completed in the geologic units penetrated by the pumped wells. Because the geologic units dip about 27 degrees to the northwest, shallow wells up dip to the southeast of the pumped well showed a good hydraulic connection to the geologic units stressed by pumping. Most observation wells down dip from the pumping well penetrated units higher in the stratigraphic section that were not well connected to the units stressed by pumping. The best hydraulic connection to the pumped wells was indicated by large drawdown in observation wells that penetrate the water-bearing unit encountered below 400 feet below land surface in wells NP–21 and NP–87. The hydraulic connection between wells NP–21 (or NP–87) and observation wells in the southern area of ground-water contamination near the BAE Systems facility is good because the observation wells probably penetrate this water-bearing unit. A 3-dimensional, finite-difference, groundwater- flow model was used to simulate flow paths and areas contributing recharge to wells for current (2000) conditions of pumping in the Colmar area and for hypothetical situations of pumping suggested by the U.S. Environmental Protection Agency that might be used for remediation. Simulations indicate that under current conditions, ground water in the northern area of contamination near the former Stabilus facility moves to the northwest and discharges mostly to West Branch Neshaminy Creek; in the southern area of contamination near BAE Systems facility, ground water probably moves west and discharges to a tributary of West Branch Neshaminy Creek near well NP–21. Model simulations indicate that if NP–21 or NP–87 are pumped at 400 gallons per minute, groundwater recharge is likely captured from the southern area of contamination, but ground-water recharge from the northern area of contamination is less likely to be captured by the pumping. Simulations also indicate that pumping of a new recovery well near BAE Systems facility at 8 gallons per minute and two new recovery wells near the former Stabilus facility at a total of about 30 gallons per minute probably would capture most of the ground-water recharge in the areas where contamination is greatest.

Water-Resources Investigations Report↗
USGS2008

Land management impacts on dairy-derived dissolved organic carbon in ground water

Dairy operations have the potential to elevate dissolved organic carbon (DOC) levels in ground water, where it may interact with organic and inorganic contaminants, fuel denitrification, and may present problems for drinking water treatment. Total and percent bioavailable DOC and total and carbon-specific trihalomethane (THM) formation potential (TTHMFP and STHMFP, respectively) were determined for shallow ground water samples from beneath a dairy farm in the San Joaquin Valley, California. Sixteen wells influenced by specific land management areas were sampled over 3 yr. Measured DOC concentrations were significantly elevated over the background as measured at an upgradient monitoring well, ranging from 13 to 55 mg L-1 in wells downgradient from wastewater ponds, 8 to 30 mg L-1 in corral wells, 5 to 12 mg L-1 in tile drains, and 4 to 15 mg L-1 in wells associated with manured fields. These DOC concentrations were at the upper range or greatly exceeded concentrations in most surface water bodies used as drinking water sources in California. DOC concentrations in individual wells varied by up to a factor of two over the duration of this study, indicating a dynamic system of sources and degradation. DOC bioavailability over 21 d ranged from 3 to 10%, comparable to surface water systems and demonstrating the potential for dairy-derived DOC to influence dissolved oxygen concentrations (nearly all wells were hypoxic to anoxic) and denitrification. TTHMFP measurements across all management units ranged from 141 to 1731 ??g L-1, well in excess of the maximum contaminant level of 80 ??g L-1 established by the Environmental Protection Agency. STHMFP measurements demonstrated over twofold variation (???4 to ???8 mmol total THM/mol DOC) across the management areas, indicating the dependence of reactivity on DOC composition. The results indicate that land management strongly controls the quantity and quality of DOC to reach shallow ground water and hence should be considered when managing ground water resources and in any efforts to mitigate contamination of ground water with carbon-based contaminants, such as pesticides and pharmaceuticals. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

Journal of Environmental Quality↗
USGS2004

Quality and sources of ground water used for public supply in Salt Lake Valley, Salt Lake County, Utah, 2001

Ground water supplies about one-third of the water used by the public in Salt Lake Valley, Utah. The occurrence and distribution of natural and anthropogenic compounds in ground water used for public supply in the valley were evaluated. Water samples were collected from 31 public-supply wells in 2001 and analyzed for major ions, trace elements, radon, nutrients, dissolved organic carbon, methylene blue active substances, pesticides, and volatile organic compounds. The samples also were analyzed for the stable isotopes of water (oxygen-18 and deuterium), tritium, chlorofluorocarbons, and dissolved gases to determine recharge sources and ground-water age. Dissolved-solids concentration ranged from 157 to 1,280 milligrams per liter (mg/L) in water from the 31 public-supply wells. Comparison of dissolved-solids concentration of water sampled from the principal aquifer during 1988-92 and 1998-2002 shows a reduction in the area where water with less than 500 mg/L occurs. Nitrate concentration in water sampled from 12 of the 31 public-supply wells was higher than an estimated background level of 2 mg/L, indicating a possible human influence. At least one pesticide or pesticide degradation product was detected at a concentration much lower than drinking-water standards in water from 13 of the 31 wells sampled. Chloroform was the most frequently detected volatile organic compound (17 of 31 samples). Its widespread occurrence in deeper ground water is likely a result of the recharge of chlorinated public-supply water used to irrigate lawns and gardens in residential areas of Salt Lake Valley. Environmental tracers were used to determine the sources of recharge to the principal aquifer used for public supply in the valley. Oxygen-18 values and recharge temperatures computed from dissolved noble gases in the ground water were used to differentiate between mountain and valley recharge. Maximum recharge temperatures in the eastern part of the valley generally are below the range of valley water-table temperatures indicating that mountain-block recharge must constitute a substantial fraction of recharge to the principal aquifer in this area. Together, the recharge temperature and stable-isotope data define two zones with apparently high proportions of valley recharge on the east side of the valley. The possibility of water samples containing a substantial proportion of water recharged before thermonuclear testing began in the early 1950s (pre-bomb) was evaluated by comparing the initial tritium concentration of each sample (measured tritium plus measured tritiogenic helium-3) to that of local precipitation at the apparent time of recharge. Three interpreted-age categories were determined for water from the sampled wells: (1) dominantly pre-bomb; (2) dominantly modern; and (3) modern or a mixture of pre-bomb and modern. Apparent tritium/helium-3 ages range from 3 years to more than 50 years. Water generally becomes older with distance from the mountain front, with the oldest water present in the discharge area. The presence of anthropogenic compounds at concentrations above reporting levels and elevated nitrate concentrations (affected wells) in the principal aquifer is well correlated with the distribution of interpreted-age categories. All of the wells (10 of 10) with dominantly modern water are affected. Seventy percent (7 of 10) of the wells with dominantly modern or a mixture of modern and pre-bomb waters are affected. Only 1 of the 11 wells with dominantly pre-bomb water is affected. Anthropogenic compounds were not detected in water with an apparent age of more than 50 years, except for water from one well. All of the samples that consisted mostly of modern water contained at least one anthropogenic compound.

Utah↗
USGS2003

Occurrence of arsenic in ground water of the Middle Rio Grande Basin, central New Mexico

Chemical data from more than 400 ground-water sites in the Middle Rio Grande Basin of central New Mexico indicate that arsenic concentrations exceed the U.S. Environmental Protection Agency drinking-water standard of 10 micrograms per liter across broad areas of the Santa Fe Group aquifer system, which is currently the almost exclusive source of drinking-water supply for residents of the basin. Identification of sources of arsenic to ground water of the basin is complicated by multiple sources of ground-water recharge that differ substantially in chemical composition. Establishment of a clear hydrologic framework for the basin was useful in interpreting the significance of patterns in arsenic concentration. This investigation indicates that there are two main sources of high-arsenic water to the Middle Rio Grande Basin. One primary source is related to silicic volcanism in the Jemez Mountains to the north, where dilute recharge water likely flows through rocks that have been altered by contact with geothermal fluids. The other primary source is mineralized water of deep origin that mixes with shallower ground water in several locations around the basin, particularly along major structural features. Ground water that has not been affected by either of these two high-arsenic sources generally has low arsenic concentrations. In some areas of the basin, values of pH exceeding about 8.5 appear to contribute to elevated arsenic concentrations through desorption of arsenic from metal oxides.

New Mexico↗
USGS2009

Ground-Water Budgets for the Wood River Valley Aquifer System, South-Central Idaho, 1995-2004

The Wood River Valley contains most of the population of Blaine County and the cities of Sun Valley, Ketchum, Haley, and Bellevue. This mountain valley is underlain by the alluvial Wood River Valley aquifer system which consists of a single unconfined aquifer that underlies the entire valley, an underlying confined aquifer that is present only in the southernmost valley, and the confining unit that separates them. The entire population of the area depends on ground water for domestic supply, either from domestic or municipal-supply wells, and rapid population growth since the 1970s has caused concern about the long-term sustainability of the ground-water resource. To help address these concerns this report describes a ground-water budget developed for the Wood River Valley aquifer system for three selected time periods: average conditions for the 10-year period 1995-2004, and the single years of 1995 and 2001. The 10-year period 1995-2004 represents a range of conditions in the recent past for which measured data exist. Water years 1995 and 2001 represent the wettest and driest years, respectively, within the 10-year period based on precipitation at the Ketchum Ranger Station. Recharge or inflow to the Wood River Valley aquifer system occurs through seven main sources (from largest to smallest): infiltration from tributary canyons, streamflow loss from the Big Wood River, areal recharge from precipitation and applied irrigation water, seepage from canals and recharge pits, leakage from municipal pipes, percolation from septic systems, and subsurface inflow beneath the Big Wood River in the northern end of the valley. Total estimated mean annual inflow or recharge to the aquifer system for 1995-2004 is 270,000 acre-ft/yr (370 ft3/s). Total recharge for the wet year 1995 and the dry year 2001 is estimated to be 270,000 acre-ft/yr (370 ft3/s) and 220,000 acre-ft/yr (300 ft3/s), respectively. Discharge or outflow from the Wood River Valley aquifer system occurs through five main sources (from largest to smallest): Silver Creek streamflow gain, ground-water pumpage, Big Wood River streamflow gain, direct evapotranspiration from riparian vegetation, and subsurface outflow (treated separately). Total estimated mean 1995-2004 annual outflow or discharge from the aquifer system is 250,000 acre-ft/yr (350 ft3/s). Estimated total discharge is 240,000 acre-ft/yr (330 ft3/s) for both the wet year 1995 and the dry year 2001. The budget residual is the difference between estimated ground-water inflow and outflow and encompasses subsurface outflow, ground-water storage change, and budget error. For 1995-2004, mean annual inflow exceeded outflow by 20,000 acre-ft/yr (28 ft3/s); for the wet year 1995, mean annual inflow exceeded outflow by 30,000 acre-ft/yr (41 ft3/s); for the dry year 2001, mean annual outflow exceeded inflow by 20,000 acre-ft/yr (28 ft3/s). These values represent 8, 13, and 8 percent, respectively, of total outflows for the same periods. It is difficult to differentiate the relative contributions of the three residual components, although the estimated fluctuations between the wet and dry year budgets likely are primarily caused by changes in ground-water storage. The individual components in the wet and dry year ground-water budgets responded in a consistent manner to changes in precipitation and temperature. Although the ground-water budgets for the three periods indicated that ground-water storage is replenished in wet years, statistical analyses by Skinner and others (2007) suggest that such replenishment is not complete and over the long term more water is removed from storage than is replaced. In other words, despite restoration of water to ground-water storage in wet years, changes have occurred in either recharge and (or) discharge to cause ground-water storage to decline over time. Such changes may include, but are not limited to: lining or abandoning canals and ditches, conversion of surface-water irriga

Scientific Investigations Report↗
USGS1990

Ground-water flow and solute movement to drain laterals, western San Joaquin Valley, California; I, Geochemical assessment

A study was undertaken to quantitatively evaluate the hydrologic processes affecting the chemical and isotopic composition of drain-lateral water in a drained agricultural field in the western San Joaquin Valley, California. The results of chemical and isotopic analysis of the samples and analysis of hydraulic-head data and drain-lateral flow data elucidate the process of mixing of deep and shallow ground water entering the drain laterals. The deep ground water was subject to partial evaporation prior to drainage-system installation and has been displaced downward (at depths greater than 6 meters) in the ground-water system. This ground water is flowing toward the drain laterals. The percentage of the deep, isotopically enriched ground water entering the drain laterals varies with time and between drain laterals. The percentage of the total drain-lateral flow, which is deep ground-water flow, is about 30 percent for the shallow drain lateral (1.8 meters below land surface) and 60 percent for the deep drain lateral (2.7 meters below land surface). During irrigation, the percentages decrease to 0 and 30 percent for the shallow and deep drain laterals, respectively. Selenium loads in the drain laterals vary with time and between drain laterals. The selenium load for the shallow drain lateral (68 kilograms) during 1 year is 21 percent of the load for the deep drain lateral (332 kilograms) because it collects less deep, high-selenium ground water and does not flow continuously. Although selenium concentrations in the drain-lateral water decreased during irrigation, selenium loads increased substantially during a preplant irrigation because of increased flow into the drain laterals. The selenium loads during 8 days of irrigation represented a substantial percentage (25 percent for the shallow drain lateral and 11 percent for the deep drain lateral) of the total selenium load for 1 year.

California↗
USGS2007

Effects of agriculture and urbanization on quality of shallow ground water in the arid to semiarid western United States, 1993-2004

Within the Western United States, agricultural and rural lands are being developed into commercial and residential areas. With changes in land use and increasing population, greater demands are placed on water resources for agricultural, industrial, and domestic supplies. Many areas in the Western United States rely exclusively on ground water as their source of drinking water. Areas that use surface-water resources often need to supplement this supply with ground water. Generally, shallow ground water is susceptible to fluctuating water quality within relatively short time scales and therefore can be used as an indicator of land-use stresses that may, in time, affect deep aquifer systems. This regional study examines data on shallow ground-water quality collected from 1993 to 2004 from 273 agricultural and 181 urban wells from 7 U.S. Geological Survey National Water-Quality Assessment study units in Arizona, California, Nevada, New Mexico, south-central Colorado, and Utah. This report determines important influences that land-use practices may have on the quality of recently recharged ground water, which may ultimately affect deep water supplies within the region.

Scientific Investigations Report↗
USGS1998

Lithological and hydrological influences on ground-water composition in a heterogeneous carbonate-clay aquifer system

The influence of clay units on ground-water composition was investigated in a heterogeneous carbonate aquifer system of Miocene age in southwest Florida, known as the Intermediate aquifer system. Regionally, the ground water is recharged inland, flows laterally and to greater depths in the aquifer systems, and is discharged vertically upward at the saltwater interface along the coast. A depth profile of water composition was obtained by sampling ground water from discrete intervals within the permeable carbonate units during coring and by squeezing pore water from a core of the less-permeable clay layers. A normative salt analysis of solute compositions in the water indicated a marine origin for both types of water and an evolutionary pathway for the clay water that involves clay diagenesis. The chemical composition of the ground water in the carbonate bedrock is significantly different from that of the pore water in the clay layers. Dissolution of clays and opaline silica results in high silica concentrations relative to water in other parts of the Intermediate aquifer system. Water enriched in chloride relative to the overlying and underlying ground water recharges the aquifer inland where the confining clay layer is absent, and it dissolves carbonate and silicate minerals and reacts with clays along its flow path, eventually reaching this coastal site and resulting in the high chloride and silica concentrations observed in the middle part of the Intermediate aquifer system. Reaction-path modeling suggests that the recharging surficial water mixes with sulfate-rich water upwelling from the Upper Floridan aquifer, and carbonate mineral dissolution and precipitation, weathering and exchange reactions, clay mineral diagenesis, clay and silica dissolution, organic carbon oxidation, and iron and sulfate reduction result in the observed water compositions.

Geological Society of America Bulletin↗
USGS1997

Ground-water, surface-water, and water-chemistry data, Black Mesa area, northeastern Arizona, 1996

The Black Mesa monitoring program is designed to document long-term effects of ground-water pumping from the N aquifer by industrial and municipal users. The N aquifer is the major source of water in the 5,400-square-mile Black Mesa area, and the ground water occurs under confined and unconfined conditions. Monitoring activities include continuous and periodic measurements of (1) ground-water pumpage from the confined and unconfined parts of the aquifer, (2) ground-water levels in the confined and unconfined areas of the aquifer, (3) surface-water discharge, and (4) chemistry of the ground water and surface water. In 1996, ground-water withdrawals for industrial and municipal use totaled about 7,040 acre-feet, which is less than a 1-percent decrease from 1995. Pumpage from the confined part of the aquifer decreased by about 3 percent to 5,390 acre-feet, and pumpage from the unconfined part of the aquifer increased by about 9 percent to 1,650 acre-feet. Water-level declines in the confined area during 1996 were recorded in 11 of 13 wells, and the median change was a decline of about 2.7 feet as opposed to a decline of 1.8 feet for 1995. Water-level declines in the unconfined area were recorded in 11 of 18 wells, and the median change was a decline of 0.5 foot in 1996 as opposed to a decline of 0.1 foot in 1995. The average low-flow discharge at the Moenkopi streamflow-gaging station was 2.3 cubic feet per second in 1996. Streamflow-discharge measurements also were made at Laguna Creek, Dinnebito Wash, and Polacca Wash during 1996. Average low-flow discharge was 2.3 cubic feet per second at Laguna Creek, 0.4 cubic foot per second at Dinnebito Wash, and 0.2 cubic foot per second at Polacca Wash. Discharge was measured at three springs. Discharge from Moenkopi School Spring decreased by about 2 gallons per minute from the measurement in 1995. Discharge from an unnamed spring near Dennehotso decreased by 1.3 gallons per minute from the measurement made in 1995; however, discharge increased slightly at Burro Spring. Regionally, long-term water-chemistry data for wells and springs have remained stable.

Open-File Report↗
USGS1999

Ground-water, surface-water, and water-chemistry data, Black Mesa area, northeastern Arizona, 1997

The Black Mesa monitoring program is designed to document long-term effects of ground-water from the N aquifer by industrial and municipal users. The N aquifer is the major source of water in the 5,400-square-mile Black Mesa area, and the ground water occurs under confined and unconfined conditions. Monitoring activities include continuous and periodic measurements of (1) ground-water pumpage from the confined and unconfined parts of the aquifer, (2) ground-water levels in the confined and unconfined parts of the aquifer, (3) surface-water discharge, and (4) chemistry of the ground water and surface water. In 1997, ground-water withdrawals for industrial and municipal use totaled about 7,090 acre-feet, which is less than a 1-percent increase from 1996. Pumpage from the confined part of the aquifer increased by about 2 percent to 5,510 acre-feet, and pumpage from the unconfined part of the aquifer decreased by about 4 percent to 1,580 acre-feet. Water-level declines in the confined part during 1997 were recorded in 5 of 12 wells; however, the median change was a rise of about 0.2 foot as opposed to a decline of 2.8 feet for 1996. Water-level declines in the unconfined part were recorded in 7 of 15 wells, and the median change was 0.0 foot in 1997 as opposed to a decline of 0.5 foot in 1996. The low-flow discharge at the Moenkopi streamflow-gaging station ranged from 1.6 to 2.0 cubic feet per second in 1997. Streamflow-discharge measurements also were made at Laguna Creek, Dinnebito Wash, and Polacca Wash during 1997. The low-flow discharge ranged from 2.3 to 4.2 cubic feet per second at Laguna Creek, 0.44 to 0.48 cubic foot per second at Dinnebito Wash, and 0.15 to 0.26 cubic foot per second at Polacca Wash. Discharge was measured at three springs. Discharge from Moenkopi School Spring increased by about 3 gallons per minute from the measurement in 1996. Discharge from an unnamed spring near Dennehotso increased by 9.9 gallons per minute from the measurement made in 1996; however, discharge decreased slightly at Burro Spring. Regionally, long-term water-chemistry data for wells and springs have remained stable. Locally, water-chemistry data for some wells have shown marked increases in concentrations of major constituents.

Arizona↗
USGS1995

Results of ground-water, surface-water, and water-chemistry monitoring, Black Mesa area, northeastern Arizona, 1994

The Black Mesa monitoring program is designed to document long-term effects of ground-water pumping from the N aquifer by industrial and municipal users. The N aquifer is the major source of water in the 5,400-square-mile Black Mesa area, and the ground water occurs under confined and unconfined conditions. Monitoring activities include continuous and periodic measurements of (1) ground-water pumpage from the confined and unconfined areas of the aquifer, (2) ground-water levels in the confined and unconfined areas of the aquifer, (3) surface-water discharge, and (4) chemistry of the ground water and surface water. In 1994, ground-water withdrawals for industrial and municipal use totaled about 7,000 acre-feet, which is an 8-percent increase from the previous year. Pumpage from the confined part of the aquifer increased by about 9 percent to 5,400 acre-feet, and pumpage from the unconfined part of the aquifer increased by about 2 percent to 1,600 acre-feet. Water-level declines in the confined area during 1994 were recorded in 10 of 16 wells, and the median change was a decline of about 2.3 feet as opposed to a decline of 3.3 feet for the previous year. The median change in water levels in the unconfined area was a rise of 0.1 foot in 1994 as opposed to a decline of 0.5 foot in 1993. Measured low-flow discharge along Moenkopi Wash decreased from 3.0 cubic feet per second in 1993 to 2.9 cubic feet per second in 1994. Eleven low-flow measurements were made along Laguna Creek between Tsegi, Arizona, and Chinle Wash to determine the amount of discharge that would occur as seepage from the N aquifer under optimal base-flow conditions. Discharge was 5.6 cubic feet per second near Tsegi and 1.5 cubic feet per second above the confluence with Chinle Wash. Maximum discharge was 5.9 cubic feet per second about 4 miles upstream from Dennehotso. Discharge was measured at three springs. The changes in discharge at Burro and Whisky Springs were small and within the uncertainty of measurement. Discharge at Moenkopi School Spring decreased from 14.6 gallons per minute in 1993 to 12.9 gallons per minute in 1994. Regionally long-term water-chemistry data for wells and springs have shown no discernible change. A recent gradual increase in concentrations of dissolved solids, sulfate, and chloride in water from Forest Lake NTUA 1, however, indicates that, locally, water from the D aquifer may be mixing with water from the N aquifer.

Arizona↗
USGS2003

Ground-water conditions in Utah, spring of 2003

This is the fortieth in a series of annual reports that describe ground-water conditions in Utah. Reports in this series, published cooperatively by the U.S. Geological Survey and the Utah Department of Natural Resources, Division of Water Resources and Division of Water Rights, provide data to enable interested parties to maintain awareness of changing ground-water conditions. This report, like the others in the series, contains information on well construction, ground-water withdrawal from wells, water-level changes, precipitation, streamflow, and chemical quality of water. Information on well construction included in this report refers only to wells constructed for new appropriations of ground water. Supplementary data are included in reports of this series only for those years or areas which are important to a discussion of changing ground-water conditions and for which applicable data are available. This report includes individual discussions of selected significant areas of ground-water development in the State for calendar year 2002. Most of the reported data were collected by the U.S. Geological Survey in cooperation with the Utah Department of Natural Resources, Division of Water Rights and Division of Water Resources.

Utah↗
USGS1996

Ground-water pumpage in the Willamette lowland regional aquifer system, Oregon and Washington, 1990

Ground-water pumpage for 1990 was estimated for an area of about 5,700 square miles in northwestern Oregon and southwestern Washington as part of the Puget-Willamette Lowland Regional Aquifer System Analysis study. The estimated total ground-water pumpage in 1990 was about 340,000 acre-feet. Ground water in the study area is pumped mainly from Quaternary sediment; lesser amounts are withdrawn from Tertiary volcanic materials. Large parts of the area are used for agriculture, and about two and one-half times as much ground water was pumped for irrigation as for either public- supply or industrial needs. Estimates of ground- water pumpage for irrigation in the central part of the Willamette Valley were generated by using image-processing techniques and Landsat Thematic Mapper data. Field data and published reports were used to estimate pumpage for irrigation in other parts of the study area. Information on public- supply and industrial pumpage was collected from Federal, State, and private organizations and individuals.

Oregon, Washington↗