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At least 397 records · Page 22Linked to original sources
USGS1997

Ground-water quality assessment of the Carson River basin, Nevada and California — Results of investigations, 1987–91

Using existing Nevada State drinking-water standards as a measure of the overall water quality, ground-water quality in principal aquifers of the upper Carson River basin is generally excellent. Ground-water quality in the Carson Desert, the distal end of the Carson River basin, displays extremes in concentrations of major and minor inorganic constituents, with dissolved solids reaching concentrations exceeding sea water. More than 10 percent of sampled ground water in the principal aquifers contain concentrations of arsenic, dissolved solids, and manganese greater than the drinking-water standards. Nearly all sampled ground water in the basin had radon-222 activities greater than the proposed Federal maximum contaminant level of 300 picocuries per liter. Uranium concentrations greater than the proposed Federal maximum contaminant level of 20 micrograms per liter were found in ground water in the adjacent Sierra Nevada.

California, Nevada↗
USGS2001

U.S. Geological Survey Ground-Water Resources Program, 2001

Ground water is among the Nation's most important natural resources. It provides drinking water to urban and rural communities, supports irrigation and industry, sustains the flow of streams and rivers, and maintains riparian and wetland ecosystems. In many areas of the Nation, the future sustainability of ground-water resources is at risk from over use and contamination. Because ground-water systems typically respond slowly to human actions and climate variability, a long-term perspective is needed to manage this valuable resource. The U.S. Geological Survey Ground-Water Resources Program provides regional evaluations, fundamental data, and predictive tools to help assure the sustainability of our Nation's ground-water resources.

Fact Sheet↗
USGS1998

Ground-water conditions in Georgia, 1997

Ground-water conditions in Georgia during 1997 and for the period of record were evaluated using data from ground-water-level and ground-water-quality monitoring networks. Data for 1997 included in this report are from continuous water-level records from 71 wells and chloride analyses from 14 wells. In 1997, annual mean ground-water levels in Georgia ranged from 6.2 feet (ft) lower to 5.6 ft higher than in 1996. Of the 71 wells summarized in this report, 23 wells had annual mean water levels that were higher, 35 wells had annual mean water levels that were lower, and 11 wells had annual mean water levels that were about the same in 1997 as during 1996. Data for two wells are incomplete because data collection was discontinued at one well, and the equipment was vandalized at one well. Record-low daily mean water levels were recorded in six wells tapping the Upper Floridan aquifer, one well tapping the Caliborne aquifer, two wells tapping the Clayton aquifer, and three wells tapping Cretaceous aquifers. These record lows were from 0.2 to 5.6 ft lower than previous record lows. Chloride concentration in water from the Upper Floridan aquifer in most of coastal Georgia was within drinking-water standards established by the Georgia Department of Natural Resources and the U.S. Environmental Protection Agency. In the Savannah area, chloride concentration has not changed appreciably with time. However, chloride concentration in water from some wells that tap the Floridan aquifer system in the Brunswick area exceeds the drinking-water standard. Ground-water-level and ground-water-quality data are essential for water assessment and management. Ground-water-level fluctuations and trends can be used to estimate changes in aquifer storage resulting from the effects of ground-water withdrawal and recharge from precipitation. These data can be used to address water-management needs and to evaluate the effects of management and conservation programs. As part of the ground-water investigations conducted by the U.S. Geological Survey (USGS), in cooperation with the State of Georgia and city and county governments, a Statewide water-level- measurement program was started in 1938. Initially, this program consisted of an observation-well network in the coastal area of Georgia to monitor variations in ground- water storage and quality. Additional wells were later included in areas where data could be used to predict potential water-resource problems. During 1997, periodic water-level measurements were made in 67 wells, and continuous water-level measurements were obtained from 151 wells. Continuous water-level records were obtained using analog (pen and chart) recorders, digital recorders that record the water level at 30-minute or 60-minute intervals, and electronic data recorders that record the water level at 60-minute intervals. For wells having incomplete water-level record, water levels during periods of missing record may have been higher or lower than recorded water levels. Water samples collected from 23 wells during April and November 1997 were analyzed to determine chloride concentration in the Savannah and Brunswick areas.

Georgia↗
USGS2007

Methods and data used to investigate polonium-210 as a source of excess gross-alpha radioactivity in ground water, Churchill County, Nevada

Ground water is the major source of drinking water in the Carson River Basin, California and Nevada. Previous studies have shown that uranium and gross-alpha radioactivities in ground water can be greater than U.S. Environmental Protection Agency Maximum Contaminant Levels, particularly in the Carson Desert, Churchill County, Nevada. Studies also have shown that the primary source of the gross-alpha radioactivity and alpha-emitting radionuclides in ground water is the dissolution of uranium-rich granitic rocks and basin-fill sediments that have their origins in the Sierra Nevada. However, ground water sampled from some wells in the Carson Desert had grossalpha radioactivities greater than could be accounted for by the decay of dissolved uranium. The occurrence of polonium-210 (Po-210) was hypothesized to explain the higher than expected grossalpha radioactivities. This report documents and describes the study design, field and analytical methods, and data used to determine whether Po-210 is the source of excess gross-alpha radioactivity in ground water underlying the Carson Desert in and around Fallon, Nevada. Specifically, this report presents: 1) gross alpha and uranium radioactivities for 100 wells sampled from June to September 2001; and 2) pH, dissolved oxygen, specific conductance, and Po-210 radioactivity for 25 wells sampled in April and June 2007. Results of quality-control samples for the 2007 dataset are also presented.

Open-File Report↗
USGS2000

Ground-water conditions in Georgia, 1999

Ground-water conditions in Georgia during 1999 and for the period of record were evaluated using data from U.S. Geological Survey ground-water-level and ground-water-quality monitoring networks. Data for 1999 included in this report are from continuous water-level records from 130 wells and chloride analyses from 14 wells. Data from one well is incomplete because data collection was discontinued. Chloride concentration in water from the Upper Floridan aquifer in most of coastal Georgia was within drinking-water standards established by the Georgia Department of Natural Resources and the U.S. Environmental Protection Agency. In the Savannah area, chloride concentration has not changed appreciably with time. However, chloride concentration in water from some wells that tap the Floridan aquifer system in the Brunswick area exceeds the drinking-water standards. Ground-water-level and ground-water-quality data are essential for water assessment and management. Ground-water-level fluctuations and trends can be used to estimate changes in aquifer storage resulting from the effects of ground-water withdrawal and recharge from precipitation. These data can be used to address water-management needs and to evaluate the effects of management and conservation programs. As part of the ground-water investigations conducted by the U.S. Geological Survey (USGS), in cooperation with the State of Georgia and city and county governments, a Statewide water-level-measurement program was started in 1938. Initially, this program consisted of an observation-well network in the coastal area of Georgia to monitor variations in ground-water storage and quality. Additional wells were later included in areas where data could be used to aid in water resources development and management. During 1999, periodic water-level measurements were made in 46 wells, and continuous water-level measurements were obtained from 165 wells. Continuous water-level records were obtained using analog (pen and chart) recorders and electronic data recorders that record the water level at 60-minute intervals. For wells having incomplete water-level record, water levels during periods of missing record may have been higher or lower than recorded water levels. Water samples collected from 85 wells during May, June, July, August, September, October, November, and December 1999 were analyzed to determine chloride concentration in the Savannah and Brunswick areas.

Georgia↗
USGS2008

Introduction to the U.S. Geological Survey National Water-Quality Assessment (NAWQA) of ground-water quality trends and comparison to other national programs

Assessment of temporal trends in national ground-water quality networks are rarely published in scientific journals. This is partly due to the fact that long-term data from these types of networks are uncommon and because many national monitoring networks are not driven by hypotheses that can be easily incorporated into scientific research. The U.S. Geological Survey (USGS) National Water-Quality Assessment Program (NAWQA) since 1991 has to date (2006) concentrated on occurrence of contaminants because sufficient data for trend analysis is only just becoming available. This paper introduces the first set of trend assessments from NAWQA and provides an assessment of the success of the program. On a national scale, nitrate concentrations in ground water have generally increased from 1988 to 2004, but trends in pesticide concentrations are less apparent. Regionally, the studies showed high nitrate concentrations and frequent pesticide detections are linked to agricultural use of fertilizers and pesticides. Most of these areas showed increases in nitrate concentration within the last decade, and these increases are associated with oxic-geochemical conditions and well-drained soils. The current NAWQA plan for collecting data to define trends needs to be constantly reevaluated to determine if the approach fulfills the expected outcome. To assist this evaluation, a comparison of NAWQA to other national ground-water quality programs was undertaken. The design and spatial extent of each national program depend on many factors, including current and long-term budgets, purpose of the program, size of the country, and diversity of aquifer types. Comparison of NAWQA to nine other national programs shows a great diversity in program designs, but indicates that different approaches can achieve similar and equally important goals. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

Conference Paper↗
USGS2001

Water resources data, Florida, water year 2000: Volume 1B: Northeast Florida ground water

Water resources data for the 2000 water year in Florida consist of continuous or daily discharge for 355 streams, periodic discharge for 17 streams, continuous or daily stage for 211 streams, periodic stage for 1 stream, peak stage and discharge for 37 streams; continuous or daily elevations for 16 lakes, periodic elevations for 45 lakes; continuous ground-water levels for 393 wells, periodic ground-water levels for 1,003 wells; quality-of-water data for 124 surface-water sites and 244 wells. The data for northeast Florida include continuous or daily discharge for 145 streams, periodic discharge for 3 streams, continuous or daily stage for 21 streams, periodic stage for 0 streams; peak stage and discharge for 0 streams; continuous or daily elevations for 12 lakes, periodic elevations for 18 lakes; continuous ground water levels for 42 wells, periodic ground water levels for 404 wells; quality-of-water data for 31 surface-water sites and 62 wells. These data represent the National Water Data System records collected by the U.S. Geological Survey and cooperating local, State and Federal agencies in Florida.

Florida↗
USGS1979

Water-level predictions for Indian Wells Valley ground-water basin, California, 1978

Ground-water pumpage in Indian Wells Valley, virtually a closed basin in the Mojave Desert of southern California, has increased gradually since 1945 and presently exceeds the long-term mean annual recharge (perennial supply). In order to aid in the understanding and management of the ground-water basin, a digital ground-water model was constructed by the U.S. Geological Survey. Since the original development of this model, conditions in the basin, including areal distribution and rates of ground-water pumpage, have changed. The results of the present simulation for the period 1969-76 constitute a second verification of the original model. Calculated heads for 1976 agree well with the observed heads, indicating a good calibration of the original model. A predictive simulation for the period 1977-2020 used pumpage values increasing from about 15,500 acre-feet per year to about 26,000 acre-feet per year. The pumpage used in this report reflects a slightly slower growth rate and a more concentrated pattern of development than that investigated when the model was originally developed. The effects of this pattern of pumpage are reflected in the water levels simulated by the model. Predicted drawdowns for 1983 are less extensive but locally more severe than those predicted earlier. The reversal of the hydraulic gradient between China Lake playa and the city of Ridgecrest, as produced by these drawdowns by the year 2020, suggests that the water-quality effects of such drawdowns should be investigated, as this could result in inferior water from the China Lake playa area flowing southward into areas of withdrawal.

California↗
USGS1970

Annotated bibliography on artificial recharge of ground water, 1955-67

Artificial ground-water recharge has become more important as water use by agriculture, industry, and municipalities increases. Water management agencies are increasingly interested in potential use of recharge for pollution abatement, waste-water disposal, and re-use and reclamation of locally available supplies. Research projects and theoretical analyses of operational recharge systems show increased scientific emphasis on the practice. Overall ground-water basin management systems generally now contain considerations of artificial recharge, whether by direct or indirect methods. Artificial ground-water recharge is a means of conserving surface runoff for future use in places where it would otherwise be lost, of protecting ground-water basins from salt-water encroachment along coastal areas, and of storing and distributing imported water. The biblio-graphy emphasizes technology; however, annotations of articles on waste-water reclamation, ground-water management and ground-water basin management are included. Subjects closely related to artificial recharge, including colloidal flow through porous media, field or laboratory instrumentation, and waste disposal by deep well injection are included where they specifically relate to potential recharge problems. Where almost the same material has been published in several journals, all references are included on the assumption that some publications may be more readily available to interested persons than others. Other publications, especially those of foreign literature, provided abstracts that were used freely as time limitations precluded obtaining and annotating all materials. Abstracts taken from published sources are noted. These are: "Abstracts of North American Geology," U.S. Department of the Interior, Geological Survey; "Abstracts of Recent Published Material on Foil and Water Conservation," ARS-41 series, Agricultural F.esearch Service, U.S. Department of Agriculture; "Water and1 Water Engineering," published by Fuel and Metallurgical Journals, Ltd., London, England; "Journal of Geophysical Research," American Geophysical Union, Washington, D.C.; "American Society of Civil Engineers Transactions," New York; "Selected Bibliography of Hydrology, United Kingdom, for the Years 1955-59," International Association of Scientific Hydrology; "Water Wells, an Annotated Bibliography," California University Water Resources Center Archives Report 13; "Re-use of Effluent in the Future With an Annotated Bibliography," by G. A. Whetstone, Texas Water Development Board Report 8, Austin, Tex.; "Journal of Water Pollution Control Federation," Washington, D.C.; and "A List of Selected Technical References on Artificial Recharge of Ground-Water Reservoirs," compiled by Roy W. Graves, Tulsa University, Information Services Department, Tulsa, Okla. Other notations are self-explanatory, and initials are those of the authors (DCS, DJG, WK). An unpublished compilation of recharge references by Arnon Arad sponsored by the United Nations Educational, Scientific, and Cultural Organization during a training period with the U.S. Geological Survey was also used. The bibliography is arranged alphabetically by author. Where an author has more than one publication, the arrangement is chronological; where an author has more than one publication in a given year, a, b, c, . . . are added. The indexing is by subject and geographic location. Each article was assigned the key words or phrases to best characterize its contents. Units of measure are as they were in the original article; abbreviations retained are generally those in common use such as mg/1 (milligrams per liter), ppm (parts per million), gpm (gallons per minute), km (kilometers), m (meters), cu m per hr (cubic meters p^r hour), cfs (cubic feet per second), me/1 (milliequivalents per liter), psi (pounds per square inch), BOD (biochemical oxygen demand), sq m (square meters), gpd (gallons per day), and mgd (million gallons per day). The bibliography was prepared because of the worldwide interest in the field of artificial recharge and the need for a single source of references to the literature published since 1954. The work is a sequel to the "Annotated Bibliography on Artificial Recharge of Ground Water Through 1954," by D. K. Todd, U.S. Geological Survey Water-Supply Paper 1477, published in 1959.

Water Supply Paper↗
USGS2006

The ground-water situation in Ohio

Present ground-water use in Ohio, approximately 650mgd (million gallons per day) amounts to about 5 percent of the water that enters the ground-water reservoirs. The largest ground-water supplies are developed where natural concentrations of water occur, chiefly in the watercourse aquifers, which consist of sand and gravel of glacial origin (outwash) in the valleys of the major streams. Other important aquifers are glacial outwash in upland areas and in the buried Teays Valley system, the limestone and dolomite aquifers in western Ohio, and sandstone and shale aquifers in the eastern half of the State. Future outlook is that more of the increasing water demand will be met from ground-water sources. Ground-water supplies will be developed at many new sites, and aquifers in areas already heavily pumped will be made to yield more water by the drilling of additional wells and recharging the aquifers artificially. Large quantities of ground water in storage, virtually unexploited, could be used for temporary low-flow augmentation of streams. Management of ground-water resources will be needed to help solve supply and distribution problems, and to resolve conflicts between users. Among future problems will be those arising from underground disposal of wastes, a practice which is expected to grow substantially from enforcement of water-quality standards for streams, set under the Federal Water Quality Act of 1965.

Ohio↗
USGS1986

Water resources data for Florida, water year 1984. Volume 1B: Northeast Florida - Ground water

Water resources data for the 1984 water year in Florida consist of continuous or daily discharge for 251 streams, periodic discharge for 32 streams, miscellaneous discharge for 43 streams, continuous or daily stage for 92 streams, periodic stage for 31 streams, peak discharge for 60 streams and peak stage for 37 streams; continuous or daily elevations for 73 lakes, periodic elevations for 82 lakes; continuous ground-water levels for 467 wells, periodic ground-water levels for 539 wells, and miscellaneous water-level measurements for 2,039 wells; quality-of-water data for 200 surface-water sites and 596 wells. The data for northeast Florida include continuous or daily discharge for 65 streams, periodic discharge for 7 streams, miscellaneous discharge for 21 streams, continuous or daily stage for 37 streams, peak discharge for 15 streams and peak stage for 8 streams; continuous or daily elevations for 22 lakes, periodic elevations for 33 lakes; continuous ground-water levels for 31 wells, periodic ground-water levels for 90 wells, and miscellaneous water-level measurements for 563 wells; quality-of-water data for 15 surface-water sites and 45 wells. These data represent the National Water Data System records collected by the U. S. Geological Survey and cooperating local, state and federal agencies in Florida.

Florida↗
USGS1987

Water resources data for Florida, water year 1986. Volume 1B. Northeast Florida - ground water

Water resources data for the 1986 water year in Florida consist of continuous or daily discharge for 277 streams, periodic discharge for 38 streams, miscellaneous discharge for 34 streams, continuous or daily stage for 77 streams, periodic stage for 20 streams, peak discharge for 88 streams, and peak stage for 69 streams; continuous or daily elevations for 69 lakes, periodic elevations for 72 lakes; continuous ground-water levels for 476 wells, periodic ground-water levels for 1,226 wells, and miscellaneous water-level measurements for 1,570 wells; quality-of-water data for 188 surface-water sites and 878 wells. The data for northeast Florida include continuous or daily discharge for 70 streams,periodic discharge for 9 streams, miscellaneous discharge for 21 streams, continuous or daily stage for 27 streams, periodic stage for 8 streams, peak discharge for 21 streams, and peak stage for 25 streams; continuous or daily elevations for 20 lakes, periodic elevations for 35 lakes; continuous ground-water levels for 40 wells, periodic ground-water levels for 105 wells, and miscellaneous water-level measurements for 589 wells; quality-of-water data for 19 surface-water sites and 82 wells. These data represent the National Water Data System records collected by the U.S. Geological Survey and cooperating local, state and federal agencies in Florida.

Florida↗
USGS1988

Water resources data, Florida, water year 1987. Volume 1B. Northeast Florida - ground water

Water resources data for the 1987 water year in Florida consist of continuous or daily discharge for 320 streams, periodic discharge for 38 streams, miscellaneous discharge for 29 streams, continuous or daily stage for 94 streams, periodic stage for 48 streams, peak discharge for 76 streams, and peak stage for 69 streams; continuous or daily elevations for 80 lakes, periodic elevations for 74 lakes; continuous ground-water levels for 477 wells, periodic ground-water levels for 562 wells, and miscellaneous water-level measurements for 2,886 wells; quality-of-water data for 223 surface-water sites and 900 wells. The data for northeast Florida include continuous or daily discharge for 125 streams, periodic discharge for 15 streams, miscellaneous discharge for 14 streams, continuous or daily stage for 45 streams, periodic stage for 27 streams, peak discharge for 26 streams, and peak stage for 27 streams; continuous or daily elevations for 39 lakes, periodic elevations for 53 lakes; continuous ground-water levels for 81 wells, periodic ground-water levels for 150 wells, and miscellaneous water-level measurements for 969 wells; quality-of-water data for 59 surface-water sites and 105 wells. These data represent the National Water Data System records collected by the U.S. Geological Survey and cooperating local, state and federal agencies in Florida.

Florida↗
USGS1989

Water resources data, Florida, water year 1989. Volume 1B: Northeast Florida ground water

Water resources data for the 1989 water year in Florida consist of continuous or daily discharge for 295 streams, periodic discharge for 36 streams, miscellaneous discharge for 75 streams, continuous or daily stage for 154 streams, continuous daily tide stage for 12 sites, periodic stage for 13 streams, peak discharge for 57 streams, and peak stage for 30 streams; continuous or daily elevations for 73 lakes, periodic elevations for 72 lakes; continuous ground-water levels for 514 wells, periodic ground-water levels for 798 wells, and miscellaneous water-level measurements for 2,687 wells; quality-of-water data for 149 surface-water sites and 827 wells. The data for northeast Florida include continuous or daily discharge for 122 streams, periodic discharge for 27 streams, miscellaneous discharge for 30 streams, continuous or daily stage for 38 streams, continuous or daily tide stage for 3 sites, periodic stage for 2 streams, peak discharge for 17 streams, and peak stage for 30 streams; continuous or daily elevations for 41 lakes, periodic elevations for 53 lakes; continuous ground-water levels for 85 wells, periodic ground-water levels for 150 wells, and miscellaneous water-level measurements for 950 wells; quality-of-water data for 60 surface-water sites and 100 wells. These data represent the National Water Data System records collected by the U.S. Geological Survey and cooperating local, state and federal agencies in Florida.

Florida↗
USGS1990

Water resources data, Florida, water year 1990: Volume 1B: Northeast Florida ground water

Water resources data for the 1990 water year in Florida consist of continuous or daily discharge for 349 streams, periodic discharge for 40 streams, miscellaneous discharge for 75 streams, continuous or daily stage for 105 streams, continuous daily tide stage for 12 sites, periodic stage for 25 streams, peak discharge for 41 streams, and peak stage for 40 streams; continuous or daily elevations for 70 lakes, periodic elevations for 70 lakes; continuous ground-water levels for 441 wells, periodic ground-water levels for 1,229 wells, and miscellaneous water-level measurements for 1,908 wells; quality-of-water data for 145 surface-water sites and 799 wells. The data for northeast Florida include continuous or daily discharge for 164 streams, periodic discharge for 27 streams, miscellaneous discharge for 22 streams, continuous or daily stage for 2 streams, continuous or daily tide stage for 3 sites, periodic stage for 13 streams, peak discharge for 17 streams, and peak stage for 30 streams; continuous or daily elevations for 41 lakes, periodic elevations for 53 lakes; continuous ground-water levels for 76 wells, periodic ground-water levels for 161 wells, and miscellaneous water-level measurements for 878 wells; quality-of-water data for 51 surface-water sites and 78 wells. These data represent the National Water Data System records collected by the U.S. Geological Survey and cooperating local, state and federal agencies in Florida.

Florida↗
USGS1993

Water resources data, Florida, water year 1992. Volume 1B: Northeast Florida ground water

Water resources data for the 1992 water year in Florida consist of continuous or daily discharge for 327 streams, periodic discharge for 20 streams, miscellaneous dis-charge for 65 streams, continuous or daily stage for 137 streams, continuous daily tide stage for 5 sites, periodic stage for 23 streams, peak discharge for 21 streams, and peak stage for 29 streams; continuous or daily elevations for 63 lakes, periodic elevations for 64 lakes; continuous ground-water levels for 430 wells, periodic ground-water levels for 1,074 wells, and miscellaneous water-level measurements for 1,501 wells; quality-of-water data for 140 surface-water sites and 683 wells. The data for northeast Florida include continuous or daily discharge for 140 streams, periodic discharge for 10 streams, miscellaneous discharge for 14 streams, continuous or daily stage for 32 streams, continuous or daily tide stage for 3 sites, periodic stage for 23 streams, peak discharge for 3 streams, and peak stage for 11 streams; continuous or daily elevations for 36 lakes, periodic elevations for 47 lakes; continuous ground-water levels for 75 wells, periodic ground-water levels for 123 wells, and miscellaneous water-level measurements for 864 wells; quality-of-water data for 38 surface-water sites and 66 wells. These data represent the National Water Data System records collected by the U.S. Geological Survey and cooperating local, state and federal agencies in Florida.

Florida↗
USGS2006

Hydraulic/Chemical Changes During Ground-Water Recharge by Injection

Ground-water recharge by injection of reclaimed water is a feasible method of improving ground-water quality in the shallow aquifer system in the Palo Alto Baylands along the San Francisco Bay. Ground water was initially more saline than sea water. Reclaimed water was injected at a rate of 10 gallons per minute from June 5, 1980, to July 1, 1980. At the completion of injection, water from an observation well 31 feet from the injection well was 98 percent injected water-in essence, fresh water. An abrupt rise in the water level in the injection well of about 1.5 feet during the initial injection test was the result of a 3.5 percent density difference between injected fresh water and saline ground water. The arrival of injected water at observation wells showed the same effect, allowing monitoring of chemical and hydraulic changes entirely through water-level data. The initially sodic clays in the confining layer were expected to swell as the saline ground water (sodium source) was diluted by recharge water. The sodium ion causes excessive coordination with the hydronium ion (H 3 O + ) in the clay lattice, resulting in expansion as the saline water is diluted. X-ray diffraction analysis of clay samples soaked first in native and then in injected water showed this effect. Calcium replaces sodium and limits expansion. Prior to injection the saline ground water was supersaturated with calcite. Dilution, as injection proceeded, eventually produced an undersaturation of calcite. An increase in well specific capacity indicates that calcite dissolved from the aquifer matrix, improving hydraulic conductivity.

Groundwater↗
USGS2004

Regional water table (2004) and water-level changes in the Mojave River and Morongo ground-water basins, Southwestern Mojave Desert, California

The Mojave River and Morongo ground-water basins are in the southwestern part of the Mojave Desert in southern California. Ground water from these basins supplies a major part of the water requirements for the region. The continuous population growth in this area has resulted in ever-increasing demands on local ground-water resources. The collection and interpretation of ground-water data helps local water districts, military bases, and private citizens gain a better understanding of the ground-water flow systems, and consequently, water availability. During March and April 2004, the U.S. Geological Survey and other agencies made almost 900 water-level measurements in about 740 wells in the Mojave River and Morongo ground-water basins. These data document recent conditions and, when compared with historical data, changes in ground-water levels. A water-level contour map was drawn using data from 500 wells, providing coverage for most of the basins. In addition, 26 long-term (as much as 74 years) hydrographs were constructed which show water-level conditions throughout the basins, 9 short-term (1992 to 2004) hydrographs were constructed which show the effects of recharge and discharge along the Mojave River, and a water-level-change map was compiled to compare 2002 and 2004 water levels throughout the basins. The water-level change data show that in the Mojave River ground-water basin, more than one half (102) of the wells had water-level declines of 0.5 ft or more and almost one fifth (32) of the wells had declines greater than 5 ft. between 2002 and 2004. The water-level change data also show that about one tenth (17) of the wells compared in the Mojave River ground-water basin had water level increases of 0.5 ft or more. Most of the water-level increases were the result of stormflow in the Mojave River during March 2004, which resulted in recharge to wells in the floodplain aquifer mainly along the river in the Alto subarea and the Transition zone, and along the river east of Barstow. In the Morongo ground-water basin, nearly one half (55) of the wells had water-level declines of 0.5 ft or more, and about one tenth (13) of the wells had declines greater than 5 ft. The Warren subbasin, where artificial-recharge operations in Yucca Valley (pl. 1) have caused water levels to rise, had water-level increases of as much as about 97 ft since 2002.

California↗