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At least 937 records · Page 52Linked to original sources
USGS1995

Simulation of ground-water flow in alluvial basins in south-central Arizona and parts of adjacent states

Numerical modeling was used to examine the character of aquifer systems in alluvial basins in south-central Arizona. The report documents the modeling approach, design and calibration procedures, and results of simulations made by using specific and general models. Transferability of geohydrologic information among basins was tested and generally proved successful. Extensive sensitivity testing was done on all models. Sensitivity to specific properties is related to geologic environment and the magnitude of predevelopment flow quantities.

Arizona, California, Nevada, New Mexico↗
USGS1998

Summary of the Southwest Alluvial Basins Regional Aquifer-System Analysis in parts of Colorado, New Mexico, and Texas

The Southwest Alluvial Basins Regional Aquifer-System Analysis in parts of Colorado, New Mexico, and Texas consists of 22 alluvial basins along and adjacent to the Rio Grande. Geochemistry, recharge, and ground-water quality in the San Luis Basin in Colorado, and the Albuquerque-Belen, Socorro, and Mesilla basins in New Mexico are described. Ground-water flow systems were simulated in the San Luis, Albuquerque-Belen, and Mesilla basins.

Professional Paper↗
USGS1996

Summary of the Snake River plain Regional Aquifer-System Analysis in Idaho and eastern Oregon

Regional aquifers underlying the 15,600-square-mile Snake River Plain in southern Idaho and eastern Oregon was studied as part of the U.S. Geological Survey's Regional Aquifer-System Analysis program. The largest and most productive aquifers in the Snake River Plain are composed of Quaternary basalt of the Snake River Group, which underlies most of the 10,8000-square-mile eastern plain. Aquifer tests and simulation indicate that transmissivity of the upper 200 feet of the basalt aquifer in the eastern plain commonly ranges from about 100,000 to 1,000,000 feet squared per day. However, transmissivity of the total aquifer thickness may be as much as 10 million feet squared per day. Specific yield of the upper 200 feet of the aquifer ranges from about 0.01 to 0.20. Average horizontal hydraulic conductivity of the upper 200 feet of the basalt aquifer ranges from less than 100 to 9,000 feet per day. Values may be one to several orders of magnitude higher in parts in individual flows, such as flow tops. Vertical hydraulic conductivity is probably several orders of magnitude lower than horizontal hydraulic conductivity and is generally related to the number of joints. Pillow lava in ancestral Snake River channels has the highest hydraulic conductivity of all rock types. Hydraulic conductivity of the basalt decreases with depth because of secondary filling of voids with calcite and silica. An estimated 80 to 120 million acre-feet of water is believed to be stored in the upper 200 feet of the basalt aquifer in the eastern plain. The most productive aquifers in the 4,800-square-mile western plain are alluvial sand and gravel in the Boise River valley. Although aquifer tests indicate that transmissivity of alluvium in the Boise River valley ranges from 5,000 to 160,000 feet squared per day, simulation suggests that average transmissivity of the upper 500 feet is generally less than 20,000 feet squared per day. Vertically averaged horizontal hydraulic conductivity of the upper 500 feet of alluvium ranges from about 4 to 40 feet per day; higher values can be expected in individual sand and gravel zones. Vertical hydraulic conductivity is considerably lower because of the presence of clay layers. Hydraulic heads measured in piezometers, interpreted from diagrams showing ground-water flow and equipotential lines and estimated by computer simulation, demonstrate that water movement is three dimensional through the rock framework. Natural recharge takes place along the margins of the plain where head decreases with depth; discharge takes place near some reaches of the Snake River and the Boise River where head increases with depth. Geothermal water in rhyolitic rocks in the western plain and western part of the eastern plain has higher hydraulic head than the overlying cold water. Geothermal water, therefore, moves upward and merges into the cold-water system. Basin water-budget analyses indicate that the volume of cold water. Carbon-14 age determinations, which indicate that residence time of geothermal water is 17,700 to 20,300 years, plus or minus 4,000 years, imply slow movement of water through the geothermal system. Along much of its length, the Snake River gains large quantities of ground water. On the eastern plain, the river gained about 1.9 million acre-feet of water between Blackfoot and Neeley, Idaho, in 1980. Between Milner and King Hill, Idaho, the river gained 4.7 million acre-feet, mostly as spring flow from the north side. Upstream from Blackfoot and in the vicinity of Lake Walcott, the rover loses flow to ground water during parts or all of the year. On the western plain, river gains from ground water are small relative to those on the eastern plain; most are from seepage. Streams in tributary drainage basins supply calcium/bicarbonate type and calcium/magnesium/bicarbonate type water to the plain. Water type is a reflection of the chemical composition of rocks in the drainage basin, Concentrations of dissolved solids are smallest, about 50 milligrams per liter, in streams such as the Boise River that drain areas of granitic rocks; concentrations are greatest, about 400 milligrams per liter, in streams such as the Owyhee and Raft Rivers that drain area of sedimentary rocks. Water chemistry reflects the interaction of surface water and ground water. The chemical composition of ground water in the plain is essentially the same as that in streamflow and groundwater discharge from tributary drainage basins. Tributary drainage basins supplied 85 percent of the ground-water recharge in the eastern plain during 1980 and a nearly equivalent percentage of the solute load in ground water; human activities and dissolution of minerals supplied the other solutes. Dissolved-solids concentrations in ground water were generally less than 400 milligrams per liter. Water from the lower geothermal system is chemically different from water from the upper cold-water system. Geothermal water typically has greater concentrations of sodium, bicarbonate, sulfate, chloride, fluoride, silica, arsenic, boron, and lithium and smaller concentrations of calcium, magnesium, and hydrogen. Difference are attributed to ion exchange as geothermal moves through the rock framework. Irrigation, mostly on the Snake River Plain, accounted for about 96 percent of consumptive water use in Idaho during 1980. The use of surface water for irrigation for more than 100 years has caused major changes in the hydrologic system on the plain. Construction of dams, reservoirs, and diversifications effected planned changes in the surface-water system but resulted in largely unplanned changes in the ground-water system. During those years of irrigation, annual recharge in the main part of the eastern plain increased to about 6.7 million acre-feet in 1980, or by about 70 percent. Most of the increase was from percolation of surface water diverted for irrigation. From preirrigation to 1952, groundwater storage increased about 24 million acre-feet, and storage decreased from 1952 to 1964 and from 1976 to 1980 because of below-normal precipitation and increased withdrawals of ground water for irrigation. Annual ground-water discharge increased to about 7.1 million acre-feet in 1980, or about 80 percent since the start of irrigation. About 10 percent of the 1980 total discharge was ground-water pumpage. About 3.1 million acres, or almost one-third of the plain, was irrigated during 1980: 2.0 million acres with surface water, 1.0 million acres with ground water, and 0.1 million acres with combined surface and ground water. About 8.9 million acre-feet of Snake River water was diverted for irrigation during 1980 and 2.3 million acre-feet of ground water was pumped from 5,300 wells. Most irrigation wells on the eastern plain are open to basalt. About two-thirds of them yield more than 1,500 gallons per minute with a reported maximum of 7,240 gallons per minute; drawdown is less than 20 feet in two-thirds of the wells. Most irrigation wells on the western plain are open to sedimentary rocks. About one-third of them yield more than 1,00 gallons per minute with a reported maximum of 3,850 gallons per minute; drawndown is less than 20 feet in about one-fifth of the wells. The major instream use of water on the Snake River Plain is hydroelectric power generation. Fifty-two million acre-feet of water generated 2.6 million megawatthours of electricity during 1980. Digital computer ground-water flows models of the eastern and western plain reasonably simulated regional changes in water levels and ground-water discharges from 1880 (preirrigation) to 1980. Model results support the concept of three-dimensional flow and the hypotheses of no underflow between the eastern and western plain. Simulation of the regional aquifer system in the eastern plain indicates that is 1980 hydrologic conditions, including pumpage, were to remain the same for another 30 years, moderate declines in ground-water levels and decreases in spring discharges would continue. Increased ground-water pumpage to irrigate an additional 1 million acres could cause ground-water levels to decline a few tens of feet in the central part of the plain and could cause corresponding decreases in ground-water discharge. A combination of actions such as increased ground-water pumpage and decreased use of surface water for irrigation (resulting in reduced recharge) would accentuate the changes.

Idaho;Oregon↗
USGS1992

Geohydrologic framework of the Snake River plain regional aquifer system, Idaho and eastern Oregon

The Snake River Plain in southern Idaho is a major geologic structure of uncertain origin. Surface geology is generally well defined, but subsurface geology is poorly defined below about 500 feet. Rocks that underlie the plain form the framework for a regional ground-water system that supplies large quantities of water for irrigation and makes the plain nationally important in terms of agricultural production. The 15,600-square-mile Snake River Plain is a grabenlike structure that formed in middle Miocene time. The graben may have been formed by oblique extensional forces resulting from interactions between the North American and Pacific tectonic plates. The oldest known rocks underlying the plain, penetrated in a 14,007-foot-deep test hole northwest of Boise, are of middle Miocene age. Miocene volcanic rocks at the plain's margin that dip toward and underlie the plain were highly faulted and se- verely eroded before the plain was formed. Faults along the margins of the eastern part of the plain are not visible at land surface and have been defined chiefly by geo- physical methods. However, well-defined fault systems bound the western part of the plain. The eastern plain is underlain predominantly by Quaternary basalt of the Snake River Group, which is intercalated with sedimentary rocks along the margins. Basalt crops out or is less than 10 feet below land surface in the central part of the east- ern plain and is usually less than 100 feet below land surface elsewhere. Geophysical data and drillers' logs indicate that Quaternary basalt in the central part of the eastern plain is as much as 5,000 feet thick. A test hole about 10 miles northeast of the Snake River near Wendell provided the first information about deep subsurface stratigraphic relations in that part of the plain. The stratigraphic sequence penetrated in the test hole is similar to that in the north wall of the Snake River canyon be- tween Milner and King Hill. In that area, basalt of the Snake River Group thins toward the river and is underlain by sedi- mentary rocks and basalt of the Tertiary and Quaternary Idaho Group. The western plain is underlain mainly by unconsolidated and weakly consolidated Tertiary and Quaternary sedimentary rocks as much as 5,000 feet thick. Basalt also is present in the west- ern plain and is most extensive near Mountain Home. Quaternary basalt of the Snake River Group, which composes much of the Snake River Plain regional aquifer system, is highly transmissive. In the eastern plain, a thick sequence of thin- layered basalt flows yields large volumes of water to wells. Wells open to less than 100 feet of the aquifer yield as much as 7,000 gallons per minute; yields of 2,000 to 3,000 gallons per minute with only a few feet of drawdown are common. Transmissivity commonly exceeds 100,000 feet squared per day and, in places, 1 million feet squared per day. Large springs in the Snake River canyon between Milner and King Hill issue at the contact between highly transmissive pil- low lava and less transmissive underlying rocks. In 1980, ground-water discharge between Milner and King Hill, largely spring flow, averaged about 6,000 cubic feet per second. In the western plain, coarse-grained sedimentary deposits are thickest and transmissivity is highest along the northern mar- gins. The percentage of coarse-grained sedimentary deposits de- creases to the southwest, where lacustrine sedimentary deposits predominate. In most of the eastern plain, the upper part of the ground- water system is unconfined. At depth and in much of the west- ern plain, aquifers are confined. Across most of the plain, Quaternary basalt aquifers overlie aquifers in the Tertiary Idavada Volcanics and Banbury Basalt of the Idaho Group. The older volcanic rocks are typically much less transmissive than the Quaternary basalt. Faults and frac- tures are permeable zones for water storage and conduits for water movement. In places near the margins of the plain, the Idavada Volcanics contains important geothermal aquifers.

Idaho;Oregon↗
USGS1995

Streamflow gains and losses in the Snake River and ground-water budgets for the Snake River plain, Idaho and eastern Oregon

Streamflow gains and losses in the Snake River demonstrate ground-water and surface-water relations and are used to develop ground-water budgets for the Snake River plain. Budgets indicate the storage in the eastern plain increased by 24 million acre-feet from 1880 to 1952 and, in the western plain, increased by about 3 million acre-feet from 1930 to 1972. Ground-water storage throughout the plain has declined in recent years, owing to climatic variations and changing irrigation practices.

Professional Paper↗
USGS1988

Solute geochemistry of the Snake River plain regional aquifer system, Idaho and eastern Oregon

Four geochemical approaches were used to determine chemical reactions controlling solute concentrations in the Snake River Plain regional aquifer system: (1) calculation of a solute balance within the aquifer, (2) identification of weathered products in the aquifer frame- work, (3) comparison of thermodynamic mineral saturation indices with plausible solute reactions, and (4) comparison of stable-isotope ratios of the solutes with those in the aquifer framework. Solutes in the geo- thermal groundwater system underlying the main aquifer were examined by calculating thermodynamic mineral saturation indices, stable-isotope ratios, geothermometry, and radiocarbon dating. Water budgets, hydrologic arguments, and isotopic analyses for the eastern Snake River Plain aquifer system demonstrate that most, if not all, water is of local meteoric and not juvenile or formation origin. Thus, the solutes must also originate within the basin. Solute balance, isotopic, mineralogic, and thermodynamic arguments suggest that about 20 per- cent of the solutes leaving the basin are derived from reactions with rocks forming the aquifer framework. Most of the remaining solutes are introduced from tributary drainage basins. Mass-balance calculations, thermodynamic arguments, and petro- graphic observations indicate that calcite and silica are precipitated in the aquifer. Petrographic evidence and thermodynamic arguments sug- gest that olivine, pyroxene, plagioclase, pyrite, and anhydrite are being weathered from the aquifer framework. Large amounts of sodium, chloride, and sulfate, relative to their concentration in the igneous rock, are being removed from the aquifer. Release of fluids from inclusions in the igneous rocks and initial flushing of grain boundaries and pores of detrital marine sediments in interbeds are believed to be a major source of these solutes. Identification and quantification of reactions controlling solute concentrations in ground water in the eastern plain indicate that the aquifer is not a large mixing vessel that simply stores and transmits water and solutes but is undergoing diagenesis and is both a source and a sink for solutes. Evaluation of solute concentrations and stable-isotope ratios of hydrogen, oxygen, carbon, and sulfur along groundwater flowpaths that transect irrigated areas suggests that irrigation water may have altered solute concentrations and isotope ratios in the eastern Snake River Plain aquifer system. The changes, however, have been small because of the similarity of solute concentrations and ratios in applied irrigation water and in native ground water, and because of rapid movement and large dispersivity of the aquifer. Reactions controlling solutes in the western Snake River basin are believed to be similar to those in the eastern basin but, because of dif- ferent hydrologic conditions, a definitive analysis could not be made. The regional geothermal system that underlies the Snake River Plain contains total dissolved solids similar to those in the overlying Snake River Plain aquifer system but contains higher concentrations of sodium, bicarbonate, silica, fluoride, sulfate, chloride, arsenic, boron, and lithium, and lower concentrations of calcium, magnesium, and hydrogen. These solutes are believed to be derived from reactions similar to those in the Snake River Plain aquifer system, except that ion exchange and hydrol- ysis play a role in controlling solute concentrations in the geothermal system. Geothermometry calculations of selected ground-water samples from known geothermal areas throughout the basin suggest that the geother- mal system is large in areal extent but has relatively low temperatures. Approximately half of the silica-quartz calculated water temperatures are greater than 90 °C. Radiocarbon dating of geothermal water in the Salmon Falls and Bruneau-Grand View areas in the south central part of the Snake River basin suggests that residence time of the geother- mal water is about 17,700 years.

Idaho;Oregon↗
USGS1988

Water use on the Snake River plain, Idaho and eastern Oregon

Amounts of water withdrawn and consumptively used for irrigation and other uses on the Snake River Plain were estimated to help deter- mine hydrologic effects of ground- and surface-water use. Irrigation is the largest off stream use of water on the plain. Surface-water irriga- tion began in the 1840's and increased rapidly through the early 1900's. Use of ground water for irrigation accelerated after World War II. In 1980, about 3.1 million acres were irrigated: 1.0 million acres were irrigated with about 2.3 million acre-feet of ground water; 2.0 million acres were irrigated with about 12.7 million acre-feet of surface water; 0.1 million acres were irrigated with combined surface and ground water. Historical changes in aquifer storage and spring discharge are closely related to changes in irrigation practices. Industries, including aquaculture, withdrew an estimated 1.97 million acre-feet of water. Withdrawals for other offstream uses, including public and rural supplies, totaled 132,000 acre-feet. Hydroelectric power generation is an economically important instream use of water. In 1980, about 52 million acre-feet of surface water was used to generate 2.6 million megawatt-hours of electricity. Native vegetation evapo- transpired an estimated 3.7 million acre-feet, and 900,000 acre-feet evaporated from bare ground and open water.

Idaho;Oregon↗
USGS1992

Hydrology and digital simulation of the regional aquifer system, eastern Snake River Plain, Idaho

The occurrence and movement of water in the regional aquifer system that underlies the eastern Snake River Plain, Idaho, de- pend on the transmissivity and storage capacity of rocks that compose the geologic framework and on the distribution and amount of recharge and discharge of water within that frame- work. On a regional scale, most water moves horizontally through interflow zones in Quaternary basalt of the Snake River Group. In recharge and discharge areas, water also moves vertically along joints and interfingering edges of basalt flows. Aquifer thickness is largely unknown, but geophysical studies suggest that locally the Quaternary basalt may exceed several thousand feet. Along the margins of the plain, sand and gravel several hundred feet thick transmit large volumes of water. Regional ground-water movement is generally from northeast to southwest, from areas of recharge to areas of discharge. Re- charge is from seepage of surface water used for irrigation, stream and canal losses, underflow from tributary drainage ba- sins, and infiltration of precipitation. Aquifer discharge is largely spring flow to the Snake River and water pumped for irrigation. Major springs are near American Falls Reservoir and along the Snake River from Milner Dam to King Hill. Regional ground-water flow was simulated with numerical models. Initially, a two-dimensional steady-state model that in- cluded a nonlinear, least-squares regression technique was used to estimate aquifer properties. Later, a three-dimensional steady- state and transient model was used to replace the two-dimen- sional model. Three-dimensional model results indicated that average total transmissivity ranged from about 0.05 to 120 feet squared per second and vertical leakance ranged from about 3 x 10 -10 to 5 x 10 -6 feet per second per foot of aquifer thickness. The three-dimensional transient model was used to compare measured and estimated long-term changes in ground-water dis- charge and water levels with simulated values. Initial head con- ditions used in transient simulations were derived from a steady-state solution of estimated preirrigation hydrologic condi- tions. Transient simulations were 5-year stress periods beginning in 1891 and ending in 1980. Recharge for each stress period from 1926 to 1980 was estimated from surface-water irrigation, pre- cipitation, and streamflow records. Recharge for stress periods from 1891 to 1925 was based on the average value for stress peri- ods from 1926 to 1980 and was indexed to estimated irrigated acreages. Average annual tributary drainage-basin underflow for stress periods from 1891 to 1910 was calculated by using basin- yield equations. Underflow for stress periods from 1911 to 1980 was varied by use of streamflow records. Transient simulations reasonably approximated measured changes in aquifer head and ground-water discharge that re- sulted from use of surface water for irrigation. Irrigation with surface water peaked in about 1950; subsequent increases in irri- gation have been supplied largely by ground water. The three- dimensional model simulated water-level declines and reduced ground-water discharge caused in part by increases in ground- water pumping. The transient model was used to simulate aquifer changes from 1981 to 2010 in response to three hypothetical development alternatives: (1) Continuation of 1980 hydrologic conditions, (2) increased pumpage, and (3) increased recharge. Simulation of continued 1980 hydrologic conditions for 30 years indicated that head declines of 2 to 8 feet might be expected in the central part of the plain. The magnitude of simulated head declines was con- sistent with head declines measured during the 1980 water year. Larger declines were calculated along model boundaries, but these changes may have resulted from underestimation of tribu- tary drainage-basin underflow and inadequate aquifer definition. Simulation of increased ground-water pumpage (an additional 2,400 cubic feet per second) for 30 years indicated head declines of 10 to 50 feet in the central part of the plain. These relatively large head declines were accompanied by increased simulated river leakage of 50 percent and decreased spring discharge of 20 percent. The effect of increased recharge (800 cubic feet per sec- ond) for 30 years was a rise in simulated heads of 0 to 5 feet in the central part of the plain.

Idaho;Oregon↗
USGS1998

Aquifer systems in the Great Basin region of Nevada, Utah, and adjacent states; summary report

Findings of the Great Basin Regional Aquifer System Analysis (RASA) are summarized. The Great Basin RASA study encompasses an area of about 140,000 square miles. Regional hydrology and ground-water hydrology of the area are described. Five models of basin-fill aquifers, a ground-water flow model of the Fish Springs system, and a regional ground-water flow model of the carbonate-rock province (eastern Nevada and western Utah) are presented and discussed.

Professional Paper↗
USGS1996

Hydrogeologic framework of the Great Basin region of Nevada, Utah, and adjacent states

Regional aquifer systems in the Great Basin consist of carbonate-rock aquifers in the eastern Great Basin and basin-fill aquifers throughout the region. In the carbonate-rock aquifers, barriers to regional flow include Precambrian crystalline basement, upper Precambrian and Lower Cambrian clastic sedimentary rocks, and Jurassic to Tertiary granitic rocks. Basin-fill aquifers are connected to carbonate-rock aquifers in the eastern Great Basin and can be hydraulically connected with each other throughout the Great Basin.

Professional Paper↗
USGS1996

Geochemistry and isotope hydrology of representative aquifers in the Great Basin region of Nevada, Utah, and adjacent states

This report briefly describes the general quality and chemical character of the ground water, discusses in detail the geochemical and hydrologic processes that produce the chemical and isotopic compositions of water in the two principal types of aquifers (basin fill and carbonate rock), delineates flow systems in carbonate-rock aquifers of southern Nevada, and discusses ground-water ages and flow velocities within the carbonate-rock systems.

Professional Paper↗
USGS1996

Ground-water flow and simulated effects of development in Paradise Valley, a basin tributary to the Humboldt River in Humboldt County, Nevada

A computer model was used to characterize ground-water flow in Paradise Valley, Nevada, and to evaluate probable long-term effects of five hypothetical development scenarios. One finding of the study is that concentrating pumping at the south end of Paradise Valley may increase underflow from the adjacent Humboldt River valley, and might affect flow in the river.

Nevada, Utah↗
USGS1998

Ground-water hydrology and simulated effects of development in the Milford area, an arid basin in southwestern Utah

A three-dimensional, finite-difference model was constructed to simulate ground-water flow in the Milford area. The purpose of the study was to evaluate present knowledge and concepts of the groundwater system, to analyze the ability of the model to represent past and current (1984) conditions, and to estimate the effects of various groundwater development alternatives. The alternative patterns of groundwater development might prove effective in capturing natural discharge from the basin-fill aquifer while limiting water-level declines. Water levels measured during this study indicate that ground water in the Milford area flows in a northwesterly direction through consolidated rocks in the northern San Francisco Mountains toward Sevier Lake. The revised potentiometric surface shows a large area for probable basin outflow, indicating that more water leaves the Milford area than the 8 acre-feet per year estimated previously. Simulations made to calibrate the model were able to approximate steady-state conditions for 1927, before ground-water development began, and transient conditions for 1950-82, during which groundwater withdrawal increased. Basin recharge from the consolidated rocks and basin outflow were calculated during the calibration process. Transient simulations using constant and variable recharge from surface water were made to test effects of large flows in the Beaver River. Simulations were made to project water-level declines over a 37- year period (1983-2020) using the present pumping distribution. Ground-water withdrawals were simulated at 1, 1.5, and 2 times the 1979-82 average rate. The concepts of "sustained" yield, ground-water mining, and the capture of natural discharge were tested using several hypothetical pumping distributions over a 600-year simulation period. Simulations using concentrated pumping centers were the least efficient at capturing natural discharge and produced the largest water-level declines. Simulations using strategically placed ground-water withdrawals in the discharge area were the most efficient at eliminating natural discharge with small water-level declines.

Utah↗