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USGS2015

Hydrology of the middle San Pedro area, southeastern Arizona

In the middle San Pedro Watershed in southeastern Arizona, groundwater is the primary source of water supply for municipal, domestic, industrial, and agricultural use. The watershed comprises two smaller subareas, the Benson subarea and the Narrows-Redington subarea. Early 21st century projections for heavy population growth in the watershed have not yet become a reality, but increased groundwater withdrawals could have undesired consequences - such as decreased base flow to the San Pedro River, and groundwater-level declines - that would lead to the need to deepen existing wells. This report describes the hydrology, hydrochemistry, water quality, and development of a groundwater budget for the middle San Pedro Watershed, focusing primarily on the elements of groundwater movement that could be most useful for the development of a groundwater model Precipitation data from Tombstone, Arizona, and base flow at the stream-gaging station on the San Pedro River at Charleston both show relatively dry periods during the 1960s through the mid-1980s and in the mid-1990s to 2009, and wetter periods from the mid-1980s through the mid-1990s. Water levels in four out of five wells near the mountain fronts show cyclical patterns of recharge, with rates of recharge greatest in the early 1980s through the mid-1990s. Three wells near the San Pedro River recorded their lowest levels during the 1950s to the mid-1960s. The water-level record from one well, completed in the confined part of the coarse-grained lower basin fill, showed a decline of approximately 21 meters. Annual flow of the San Pedro River, measured at the Charleston and Redington gages, has decreased since the 1940s. The median annual streamflow and base flow at the gaging station on the river near Tombstone has decreased by 50 percent between the periods 1968–1986 and 1997–2009. Estimates of streamflow infiltration along the San Pedro River during 1914–2009 have decreased 44 percent, with the largest decreases in the months June–October in the Benson subarea. In the Narrows-Redington subarea, streamflow infiltration has decreased about 65 percent during 1914–2009. The average annual outflow (27.6 hm 3 /year [cubic hectometers per year]) from the Benson subarea aquifer for water years 2001 through 2009 exceeded the inflows (20.0 hm 3 / yr) by 7.60 hm 3 /yr. In the Narrows-Redington subarea for the same period, the average annual outflow (15.7 hm 3 /yr) from the aquifer system exceeded the inflows (13.8 hm 3 /yr) by nearly 2 hm 3 /yr. The largest withdrawals of groundwater in both subareas are for irrigation; these withdrawals peaked in 1973 and have been steadily decreasing since then. Recharge from streamflow infiltration exceeded recharge from the mountain-front and from ephemeral channels in the Benson subarea. In the Narrows-Redington subarea, however, recharge from mountain-front and ephemeral channel recharge exceeded recharge from streamflow infiltration. Evapotranspiration by phreatophytes accounts for the largest outflow of groundwater for both subareas—78 percent of the outflow in the Narrows-Redington subarea and 62 percent of the outflow in the Benson subarea. Precipitation, surface-water, and groundwater chemistry and isotope data indicated the relative age and residence time of groundwater, the amount of interaction between geologic sources and groundwater, and how recharge elevation and season were related to the presence of modern water. The bedrock aquifer receives modern recharge (

Arizona↗

USGS1983

Numerical simulation of the alluvium and terrace aquifer along the North Canadian River from Canton Lake to Lake Overholser, central Oklahoma

Alluvium and terrace deposits of Quaternary age, which cover an area of about 400 square miles along the North Canadian River between Canton Lake and Lake Overholser, locally yield as much as 500 gallons per minute to wells. The deposits are as much as 100 feet thick and consist of clay, silt, sand, and gravel, with sand-sized material dominating. The underlying bedrock is Permian sandstone and shale. The amount of water stored in the aquifer during 1980 was estimated to be 4.00 x 1010 cubic feet. A digital model was used to estimate the ability of the aquifer to continue to supply water for irrigation, industry, and domestic use. A block-centered, finite-difference model with 1 mile node spacing was used to project the amount and distribution of water in the aquifer in the future. The model was calibrated using the aquifer discharge to the North Canadian River and the difference between computed and measured heads. The model was calibrated using recharge rate of 1 inch per year, a horizontal hydraulic conductivity of 4.5 x 10 -4 feet per second and a specific yield of 0.16. Model simulations using the 1979 pumping rate, a projected pumping rate (based on expected increases in water use), and double the projected increase in pumping rate were made to 1993. With the 1979 pumping rate, the volume of water in storage in 1993 is 3.88 x 10 10 cubic feet and ground-water discharge to the North Canadian River is 10.9 cubic feet per second. With the projected pumping increase, the volume of water in storage is 3.81 x 1010 cubic feet and ground-water discharge to the stream is 6.91 cubic feet per second. At double the projected increase in pumping rate, the volume of water in storage is 3.74 x 1010 cubic feet and the ground-water discharge is 2.93 cubic feet per second.

Water-Resources Investigations Report↗

USGS1966

Ground-water resources and geology of northern and central Johnson County, Wyoming

Northern and central Johnson County, Wyo., is an area of about 2,600 square miles that lies principally in the western part of the Powder River structural basin but also includes the east flank of the Bighorn Mountains. Sedimentary rocks exposed range in age from Cambrian to Recent and have an average total thickness of about 16,000 feet. Igneous and metamorphic rocks of Precambrian age crop out in the Bighorn Mountains. Rocks of pre-Tertiary age, exposed on the flanks and in the foothills of the Bighorns, dip steeply eastward and lie at great depth in the Powder River basin. The rest of the project area is underlain by a thick sequence of interbedded sandstone, siltstone, and shale of Paleocene and Eocene age. Owing to the regional structure, most aquifers in Johnson County contain water under artesian pressure. The Madison Limestone had not been tapped for water in Johnson County at the time of the present investigation (1963), but several wells in eastern Big Horn and Washakie Counties, on the west flank of the Bighorn Mountains, reportedly have flows ranging from 1,100 to 2,800 gallons per minute. Comparable yields can probably be obtained from the Madison in Johnson County in those areas where the limestone is fractured or cavernous. The Tensleep Sandstone reportedly yields 600 gallons per minute to a pumped irrigation well near its outcrop in the southwestern part of the project area. Several flowing wells tap the formation on the west flank of the Bighorn Mountains. The Madison Limestone and the Tensleep Sandstone have limited potential as sources of water because they can be developed economically only in a narrow band paralleling the Bighorn Mountain front in the southwestern part of the project area. Overlying the Tensleep Sandstone is about 6,000 feet of shale, siltstone, and fine-grained sandstone that, with a few exceptions, normally yields only small quantities of water to wells. The Cloverly Formation and the Newcastle Sandstone may yield moderate quantities of water to wells; but, in some areas, properly constructed wells tapping both formations might yield large quantities of water. The Shannon Sandstone Member of the Cody Shale will probably yield only small quantities of water to Wells, but it is the best potential source of ground water in the stratigraphic interval between the Newcastle and Parkman Sandstones. The Parkman Sandstone and the Lance Formation yield water to relatively shallow wells principally in the southwestern part of the project area. The Fort Union Formation yields adequate supplies of water for stock and domestic use from relatively shallow wells near its outcrop almost everywhere in the county. A few deep wells tap the Fort Union along the Powder River valley in the northeastern part of Johnson County. Some of these wells flow, but their flows rarely exceed 10 gallons per minute; larger yields could be undoubtedly be obtained by pumping. The Wasatch Formation is the principal source of ground water in Johnson County. It yields adequate supplies to many relatively shallow stock and domestic wells, some of which flow, but much larger yields probably would require pumping lifts that are prohibitive for most purposes. The Kingsbury Conglomerate and Moncrief Members of the Wasatch Formation, though, may yield moderate quantities of water in some places. Alluvial deposits underlying the valleys of the Powder River and Crazy Woman, Clear, and Piney Creeks are potential sources of moderate to large supplies of water in the Powder River drainage basin. The permeability of these deposits decreases with distance from the Bighorn Mountain front, so that largest yields can probably be obtained along the upper reaches of these streams. Most ground water utilized in the project area is for domestic and stock supplies and is obtained from drilled wells and from springs. Water for irrigation is obtained almost entirely by diverting flows of perennial streams. The discharge of wel

Water Supply Paper↗

USGS2015

Insights into controls on hexavalent chromium in groundwater provided by environmental tracers, Sacramento Valley, California, USA

Environmental tracers are useful for determining groundwater age and recharge source, yet their application in studies of geogenic Cr(VI) in groundwater has been limited. Environmental tracer data from 166 wells located in the Sacramento Valley, northern California, were interpreted and compared to Cr concentrations to determine the origin and age of groundwater with elevated Cr(VI), and better understand where Cr(VI) becomes mobilized and how it evolves along flowpaths. In addition to major ion and trace element concentrations, the dataset includes δ 18 O, δ 2 H, 3 H concentration, 14 C activity (of dissolved inorganic C), δ 13 C, 3 He/ 4 He ratio, and noble gas concentrations (He, Ne, Ar, Kr, Xe). Noble gas recharge temperatures (NGTs) were computed, and age-related tracers were interpreted in combination to constrain the age distribution in samples and sort them into six different age categories spanning from <60 yr old to >10,000 yr old. Nearly all measured Cr is in the form of Cr(IV). Concentrations range from <1 to 46 μg L −1 , with 10% exceeding the state of California’s Cr(VI) maximum contaminant level of 10 μg L −1 . Two groups with elevated Cr(VI) (⩾5 μg L −1 ) were identified. Group 1 samples are from the southern part of the valley and contain modern (<60 yr old) water, have elevated NO 3 − concentrations (>3 mg L −1 ), and commonly have δ 18 O values enriched relative to local precipitation. These samples likely contain irrigation water and are elevated due to accelerated mobilization of Cr(VI) in the unsaturated zone (UZ) in irrigated areas. Group 2 samples are from throughout the valley and typically contain water 1000–10,000 yr old, have δ 18 O values consistent with local precipitation, and have unexpectedly warm NGTs. Chromium(VI) concentrations in Group 2 samples may be elevated for multiple reasons, but the hypothesis most consistent with all available data (notably, the warm NGTs) is a relatively long UZ residence time due to recharge through a deep UZ near the margin of the basin. A possible explanation for why Cr(VI) may be primarily mobilized in the UZ rather than farther along flowpaths in the oxic portion of the saturated zone is more dynamic cycling of Mn in the UZ due to transient moisture and redox conditions.

California↗

USGS1967

Ground water in the Eola-Amity Hills area, northern Willamette Valley, Oregon

The Eola-Amity Hills area ,comprises about 230 square miles on the west side of the Willamette Valley between Salem and McMinnville, Oreg. The area is largely rural, and agriculture is the principal occupation. Rocks ranging in age from Eocene to Recent underlie the area. The oldest rocks are a sequence more than 5,000 feet thick of marine-deposited shale and siltstone strata, with thin interbeds of sandstone that range in age from Eocene to middle Oligocene. They are widely exposed in and west of the Eola-Amity Hills and underlie younger sedimentary and volcanic rocks throughout the study area. In the Eola-Amity Hills and Red Hills of Dundee, the Columbia River Group, a series of eastward-dipping basaltic lava flows locally of Miocene age, and conformably overlies the marine sedimentary rocks. The Columbia River Group ranges in thickness from less than 1 foot to about 900 feet and has an average thickness of about 200 feet. The formation is exposed in the Eola-Amity Hills and Red Hills of Dundee and, at places, extends to the east beneath younger rocks. Overlying the Columbia River Group and marine sedimentary rocks are nonmarine sedimentary deposits that range in thickness from less than 1 foot, where they lap up (to an altitude of about 200 ft) on the flanks of the higher hills, to several hundred feet along the east margin of the study area. These deposits include the Troutdale Formation of Pliocene age, the Willamette Silt of late Pleistocene age, and alluvium of the Willamette River and its tributaries. The Troutdale Formation and the alluvium of the Willamette River contain the most productive aquifers in the Eola-Amity Hills area. These aquifers, which consist mainly of sand and gravel, generally yield moderate to large quantities of water to properly constructed wells. Basalt of the Columbia River Group yields small to moderate quantities of water to wells, and the marine sedimentary rocks and Willamette Silt generally yield small but adequate quantities of water for domestic and stock supplies. Ground water from the Columbia River Group and nonmarine sedimentary rocks is chemically suitable for irrigation and other uses, as is the water from shallow depths in the marine sedimentary rocks. However, water from depths of more than several hundred feet in the marine sedimentary rocks contains large amounts of chloride and other dissolved mineral constitutents that make it unsuitable for most uses. Samples from three fairly closely spaced wells obtaining water from depth zones of 50 to 77, 191 to 201, and about 2,000 feet contained 172, 1,160, and 26,000 ppm (parts per million) of chloride, respectively. About 6,100 acre-feet of ground water was pumped from wells and withdrawn from springs for various uses during 1964; of this amount about 4,800 acre-feet was used for irrigation. The total volume of ground water withdrawn and put to beneficial use each year is small compared with the amount that discharges naturally by evapotranspiration and through undeveloped seeps and springs. Much of the natural discharge could be intercepted and put to beneficial use by pumping from wells. Major problems affecting the development of ground water in the area include a) uneven areal distribution of permeable rocks, (b) undesirable chemical quality of the ground water locally in the marine sedimentary rocks, and (c) fine sand entering wells that tap the Troutdale Formation and thereby causing loss of well efficiency and costly wear on pumps and water-supply systems.

Water Supply Paper↗

USGS1963

Ground-water exploration in Al Marj area, Cyrenaica, United Kingdom of Libya

The present report, based largely on fieldwork during 1959-61, describes the results of reconnaissance hydrogeologic studies and exploratory drilling to evaluate the general water-bearing properties of the rocks and the availability of groundwater supplies for irrigation, stock, and village uses in Al Marj area. These studies and the drilling were conducted under the auspices of the U.S. Operations Mission of the International Cooperation Administration. Al Marj area, located in the Province of Cyrenaica on the southern coast of the Mediterranean Sea, contains a land area of about 6,770 square kilometers. Along the Mediterranean shore is a narrow coastal plain that rises evenly to the base of an escarpment that forms the seaward front of an undulating plateau known as. Al Jabal al Akhgiar. The climate is semiarid; seasonal rainfall occurs during the winter months. Owing to orographic effects, the rainfall is somewhat higher in the Jabal than in the coastal plain. The average annual rainfall ranges from about 250 millimeters in the coastal plain to 450 millimeters on the Jabal. All the streams (wadis) of the area are ephemeral and flow only in response to heavy rains of the winter season. From a drainage divide on the Jabal some streams flow north and northwest toward the sea and the others, south and southeast to the interior desert. Solution features, such as limestone sink holes, are common in the coastal plain and a large solution depression occurs near Al Marj. The rocks of A1 Marj area consist predominantly of limestone and some sandstone and shale; they range from Cretaceous to Miocene age. On the coastal plain Miocene limestone is locally mantled by Quaternary alluvial, beach and lagoonal deposits. The Miocene and older beds have a regional southerly dip. These rocks are broken by northeast-trending normal faults in the coastal and inland escarpments. The ground-water reservoir is contained chiefly in fractures, bedding planes, and solution openings in the limestone country rock. The upper limit of this reservoir is marked by a water table which generally lies within 40 meters of the land surface in the coastal plain but is 100 meters or more below the surface of most of the Jabal and the interior desert. The ground-water reservoir is replenished chiefly by infiltration from surface-water runoff in wadis and to less extent by direct infiltration of rainfall. Ground water moves north and northwest toward the Mediterranean Sea and south toward the interior desert from a ground-water divide near the crest of A1 Jabal al Akhgiar. Discharge of ground water takes place by submarine outflow, spring flow, evapotranspiration, and withdrawals from wells. Wells, springs, and cisterns furnish almost all water supplies for municipal, village, stock and irrigation purposes. Bengasi, A1 Marj, and A1 Abyar are the only centers of population with municipal distribution systems. Drafts from individual dug wells used for irrigation in the coastal plain generally are no more than 10 to 15 cubic meters per day. In the Jabal and the interior desert drafts from individual stock and village wells are generally less than 10 cubic meters per day and from most wells only a few thousand liters per day. Some 21 test wells were put down during the present investigation to depths ranging from 30 to 309 meters. The yields obtained by test pump and bailer ranged from 45 to 0.6 cubic meters per hour. With few exceptions, well yields sufficient for stock and village requirements were obtained. Well yields sufficient for irrigation even on a moderate scale, however, are not everywhere available. In the Jabal and the interior desert the ground water is generally of good to fair chemical quality and suitable for most purposes. In the coastal plain, however, the ground water is in places moderately to highly mineralized, and consequently for irrigation use it must be applied to the land under optimum crop soil, and drainage conditions.

Water Supply Paper↗

USGS1953

Ground-water resources of the Rapid Valley unit, Cheyenne Division, South Dakota, with a section on the surface waters of Rapid Valley

The Rapid Valley unit is in Pennington County, S. Dak., and extends from the east city limits of Rapid City southeastward for 21 miles along Rapid Creek. The bedrock formations that underlie the region are chiefly marine in origin, and they generally dip eastward from the center of the Black Hills uplift. The exposed formations are of Cretaceous age and consist of the Greenhorn limestone, the Carlile shale, the Niobrara formation, and the Pierre shale. The Pierre shale, which underlies the unconsolidated flood plain and terrace deposits in much Of the region is exposed in the erosional slopes along the south side of the valley and in the deeper draws on the north side. The areas in which the other formations are exposed are relatively small and are restricted to the western part of-the region. Four terraces are present on the north side of Rapid Creek. The lowest terrace and the flood plain in the western half of the region are irrigated at the present time, and the two lower terraces and the flood plain in the eastern half have been proposed for irrigation. Abundant supplies of ground water occur in the flood plain and terrace deposits where they are now irrigated. Because the waterbearing materials consist of interfingering layers of differing permeability, the ground water is under water-table conditions in some places whereas it is confined in others. Locally, where there is a confining layer below other water-bearing materials or where a confined layer is itself saturated, the ground water may occur under both water-table and artesian conditions. Seepage from irrigation canals, which is the principal source of recharge, causes high ground-water levels from June to November; as a result, parts of the areas have become waterlogged. In the parts of the region that are not now affected by irrigation, the surface of the ground water is only a few feet above the bedrock surface and 6 ft to 42 ft below land surface; its position is relatively constant throughout the year. Harmful concentrations of salt in the soil are in part due to evaporation of ground water. These are found only locally in the Rapid Valley region and do not present a serious problem at this time. It is thought, however, that the fine-grained materials underlying the Rapid terrace may contain sufficient salt to cause detrimental salt accumulations in the soil if the proposed irrigation causes ground-water levels to rise close to the surface. Lining of the irrigation canals would reduce the amount of seepage and would effect a lowering of ground-water levels, if irrigation practices are extended to other areas, drainage facilities will be necessary both to avoid aggravating the existing conditions of waterlogging and to prevent the waterlogging of other low-lying lands. The flow of Rapid Creek is affected by a variety of conditions. A few miles west of Rapid City, where Rapid Creek flows over the Englewood and Pahasapa limestones and the Minnelusa sandstone, there is a loss of about 8 cfs of water in a distance of a few miles. In the 3-mile reach of Rapid Creek between the Canyon Lake stream-gaging station and the Rapid City stream-gaging station there is a gain of about 20 cfs; much of this gain in flow may be attributed to the inflow from Cleghorn and Jackson springs and to the addition of water from the State-owned cement plant. In the Rapid Valley unit, the flow of the creek during the irrigation season is affected largely by the amount of water diverted for irrigation. The irrigation canals act as bypass channels, much of the water being returned to Rapid Creek by way of spillage into normally dry tributary creek channels and by movement through ground-water bodies that discharge into Rapid Creek.

South Dakota↗

USGS1977

Geohydrology of part of the Round Valley Indian Reservation, Mendocino County, California

The Round Valley Indian Reservation in northern California obtains most of its water from the ground-water reservoir. The ground-water reservoir is made up of continental deposits, alluvium, and stream-channel deposits ranging in age from Pliocene to Holocene. Most of the water is pumped from the alluvium. Most ground water (about 20,000 acre-feet or 25 cubic hectometers per year) is derived from stream seepage. Natural discharge (discharge to streams, evapotranspiration, and underflow) has averaged about 21,000 acre-feet per year. Pumping and flow from artesian wells has averaged about 2,750 acre-feet per year. Ground water occurs in both confined and unconfined aquifers. The ground-water reservoir is full, and about 230,000 acre-feet of water is stored in the depth interval 10-200 feet. The water is chemically and biologically suitable for domestic or irrigation use, although hardness is high for domestic use and, locally, dissolved iron is a problem. There is potential for developing additional ground-water supplies. (Woodard-USGS)

Water-Resources Investigations Report↗

USGS1970

Water resources and related geology of Dera Ismail Khan district, West Pakistan, with reference to the availability of ground water for development

Dera Ismail (D.I.) Khan District contains an area of 3,450 square miles between the right bank of the Indus River and the Sulaiman Range in westcentral West Pakistan. Agriculture is the principal source of income in the District, but only a small part of the arable land is fully utilized. The region is semiarid and has an average annual rainfall of about 9 inches and a potential evapotranspirational rate of eight to nine times the annual rainfall. Thus, rainfall alone is not adequate for high-intensity cropping. Irrigation is practiced near the Indus River; the Paharpur Canal is used, as well as the traditional inundation method. Elsewhere in the District, adequate water is supplied to local areas by karezes, perennial streams from the mountains, and some recently installed tubewells (see 'Glossary'). Further development of ground-water supplies would permit a more effective utilization of most of the presently tilled land and would allow additional land to be farmed. D.I. Khan District is primarily an alluvial plain that slopes from the mountain ranges in the northern and western parts of the District toward the Indus River. Rocks in the bordering mountains are of Paleozoic to early or middle Pleistocene age. The unconsolidated rocks of the plain, of middle (?) Pleistocene to Holocene (Recent) age, consist of piedmont deposits derived from the hills to the north and west and of alluvium laid down by the Indus River. These deposits interfinger in a transitional zone about 8 to 12 miles west of the river. Lithologic and structural features indicate that the unconsolidated rocks possibly may be divided into broad units. The investigations in D.I. Khan District have revealed two main areas of potential ground-water development based on considerations of both permeability and chemical quality of the ground water: 1. A belt about 10 miles wide parallels the Indus River from the Khisor Range southward to the area immediately south of D.I. Khan town. In this belt, the material penetrated by test holes and tubewells consists predominantly of sand, which in tubewells can yield from 2 to 3 cfs (cubic feet per second) of water with only moderate drawdown. Also in this belt, ground water of good chemical quality extends to depths of 1,000 feet or more. 2. The area from the mouth of the Gumal River gorge to the vicinity of Kot Azam contains sand and gravel strata that may yield from 1 to 3 cfs of water, which contains 500 to 1,500 ppm (parts per million) of total dissolved solids. Other marginal parts of the District also contain water of good chemical quality, but developmental prospects are somewhat poorer because of greater depths to water, lower permeabilities, or greater depths to aquifers, all of which would require greater costs in the tubewell installations. The stratification or zoning of water of different chemical qualities to some extent governs the local availability of useful water. Generally, the ground water of poorest quality is found in the shallow zone, and quality improves with depth. The central part of the District, in a belt reaching from the vicinity of Tank southward to the Indus River near Dera Ghfizi Khan District, contains highly mineralized water and few aquifers. The mineralization of water in this belt is due primarily to large concentrations of sodium and sulfate and thus differs from the main part of the Punjab region where highly mineralized waters are generally chloride waters. Radical changes in water quality, both horizontally and vertically, are common in the District. Changes in chemical quality of water from large-capacity wells near areas of highly mineralized water are taking place, and further changes may be expected as withdrawals continue and increase in magnitude. Under present conditions, surface-water supplies are fully utilized, and ground water is the largest supply available for development-other than that from the Indus River.

Water Supply Paper↗

USGS2009

Sedimentation survey of Lago Guerrero, Aguadilla, Puerto Rico, March 2006

Lago Guerrero is located in Aguadilla, northwestern Puerto Rico (fig. 1). The reservoir has a surface area of about 32,000 square meters and is excavated in Aymamon Limestone of Miocene age. This bedrock consists of chalk interbed-ded with solution-riddled hard limestone (Monroe, 1969). The reservoir was constructed in the 1930s as part of the Isabela Hydroelectric System to regulate flows to two hydroelectric plants-Central Isabel No. 2, at an elevation of about 110 meters above mean sea level, and Central Isabel No. 3, at about 55 meters above mean sea level. Hydroelectric power generation was discontinued during the early 1960s, although the exact date is unknown (Puerto Rico Electric Power Authority, written commun., 2007). The principal use of the reservoir since then has been to regulate flow to two public-supply water filtration plants and supply irrigation water for the Aguadilla area. Flow into the reservoir is derived from Lago Guajataca through a 26-kilometer-long Canal Principal de Diversion concrete canal (Puerto Rico Electric Power Authority, written commun., 2001). Additional inflow occurs on an incidental basis only during intensive rainfall from the immediate drainage area. The present Lago Guerrero drainage area is undetermined, due to the irregular and complex topography of the limestone terrain and anthropogenic modifications to the stormwater drainage system. Stormwater runoff, however, is presumed to be negligible compared to the almost constant inflow to the reservoir of about 59,300 cubic meters per day from Lago Guajataca (CSA Group, 2000). On March 9, 2006, the U.S. Geological Survey (USGS), Caribbean Water Science Center, in cooperation with the Puerto Rico Electric Power Authority (PREPA), conducted a bathymetric survey of Lago Guerrero to determine the storage capacity of the reservoir and sedimentation amount since a previous survey conducted on May 30, 2001. The March 2006 survey was made to develop a bathymetric map of the reservoir, establish baseline data for future reservoir capacity comparisons, and to estimate the average sedimentation rate over the preceding 5 years.

Puerto Rico↗

USGS1964

Water resources of the Green Bay area, Wisconsin

The Green Bay area comprises an area of about 525 square miles in eastern Wisconsin at the south end of Green Bay. It includes the western three-fourths of Brown County and the eastern one-ninth of Outagamie County. In 1960, the population of the area was estimated at 124,000. The most prominent topographic feature is the northwest-facing, southwestward trending Niagara escarpment. The area northwest of the escarpment drains into Green Bay via the Fox River, Suamico River, Duck Creek, and their tributaries. The area southeast of the escarpment is drained by streams that flow into Lake Michigan. The chief sources of surface water in the Green Bay area are the Fox River, Green Bay, and Lake Michigan. Smaller amounts of water are available from the East and Suamico Rivers and other streams. A sandstone aquifer is the principal source of the ground-water supply. The Niagara dolomite, although largely undeveloped, is potentially an important aquifer in the eastern part of the area. Small amounts of water are obtained also from the Platteville formation and from deposits of Pleistocene and Recent age. Water from the surfaceand ground-water sources is moderately hard to very hard. The Fox River, tributary to Lake Michigan at Green Bay, is a significant source of water for industrial use in the Green Bay area. The Menasha Dam, which controls release of water from the Lake Winnebago pool, is the major regulation on the Fox River, and it has considerable effect in reducing peak flows and supplementing low flows in the lower Fox River. The average discharge of the lower Fox River for the period 1898-1959, as measured at the gaging station at Rapide Croche Dam, was 2,687 mgd (million gallons per day). The longest consecutive period during which the discharge averaged less than 500 mgd was 80 days. The average discharge can be expected to fall below 700 mgd about once every 5 years for a 7-day period. In 1959, the average withdrawal of water from the Fox River was about 62 mgd. The water in the river is of the calcium magnesium bicarbonate type and is hard. The small streams in the area are utilized chiefly for stock watering; some of the water, however, is used for irrigation. The water in the small streams is more highly mineralized than the water in the Fox River and is very hard. Large quantities of water are available from Green Bay, but the disposal of industrial waste into the bay has restricted the use of the water. The major withdrawal is for condenser cooling, and, in 1959, it averaged about 415 mgd. The water from Green Bay is moderately hard but is of better chemical quality than the water from the Fox River and the small streams in the area. The only withdrawals of water from Lake Michigan for use in the Green Bay area are made by the city of Green Bay. In 1959, these withdrawals averaged 7.8 mgd. The lower Fox River is not subject to extremes of flow owing to the dampening effect of the Lake Winnebago pool and the regulation of flow at Menasha Dam. Cloudbursts over the lower Fox River valley below Menasha Dam, however, have occasionally caused extremely high water, as in 1922, when the discharge at the mouth of the Fox River was estimated to be about 50,000 mgd. Daily discharges greater than about 13,000 mgd occurred only 7 times in the period 1918-59. The 50-year flood of 15,500 mgd represents an average runoff of less than 2.6 mgd per square mile of drainage area, a relatively low runoff for a 50-year flood in Wisconsin. The sandstone aquifer is the principal source of ground water in the Green Bay area and furnishes water for public supply and industrial use. This aquifer includes rocks of Late Cambrian age, and the Prairie du Chien group and St. Peter sandstone of Ordovician age; it ranges in thickness from 550 to 640 feet. Ground water is found in openings along fractures and bedding planes and in the interstices between sand grains. The sandstone aquifer can support additional development of large supplies of ground water. Wells can be developed in most of the area that will yield 500 gpm (gallons per minute) or more, provided they are properly spaced and penetrate the entire thickness of the aquifer. It is estimated that the perennial yield of the sandstone in the Green Bay area could be at least 30 mgd if the aquifer is properly developed; only 5.4 mgd was withdrawn in 1959. The water from this sandstone aquifer is of the calcium magnesium bicarbonate type, is very hard, and, at a few places, contains objectionable amounts of iron. The Niagara dolomite, potentially a source of moderate to large quantities of water in the eastern part of the area, probably will yield 500 gpm or more to wells. In 1959, the average withdrawal of water for all uses was estimated at 495 mgd, of which 98.2 percent was from surface-water sources and 1.8 percent was from wells. About 485 mgd of water was withdrawn for industrial use, 6 mgd for public supply, and 4 mgd for rural use. The industrial use of water averaged 441 mgd for condenser cooling, 38 mgd fot processing by the paper industry, and 6 mgd for other industrial uses. The city of Green Bay used 7.8 mgd of water from Lake Michigan; other public supplies in the area used 2.6 mgd from wells. Of the withdrawals of water for rural use, about 75 percent was from wells and about 25 percent was from streams. The discharge of wastes into the lower Fox River and its tributary streams has altered the quality of the natural water. The wastes consist chiefly of treated municipal sewage and treated and untreated wastes from the paper industry, rendering plants, a sugar mill, and other industries. The industrial waste makes up about 90 percent of the oxygen-demand loading in the lower Fox River, and treated municipal sewage accounts for about 10 percent. The dissolved-oxygen concentration of water in the lower Fox River decreases rapidly in the vicinity of Green Bay during the summer when the river water is warm. If the periods when the river water is warmest, generally during July and early August, were to coincide with periods of lowest annual streamflow, generally in late August, the river would be unable to assimilate the loading of decomposable organic matter. In an emergency, industrial and public supply wells could supply at least 6 mgd for a sustained period and probably as much as 10 mgd for a period of several days. Six of the wells that formerly supplied the city of Green Bay are maintained in operating condition and could furnish about the same quantity of water as the industrial and other public supply wells. Small streams in the area would be supplemental sources of water, and the water in the Fox River and Green Bay is easily accessible.

Wisconsin↗

USGS2006

Hydrogeologic framework refinement, ground-water flow and storage, water-chemistry analyses, and water-budget components of the Yuma area, southwestern Arizona and southeastern California

The ground-water and surface-water system in the Yuma area in southwestern Arizona and southeastern California is managed intensely to meet water-delivery requirements of customers in the United States, to manage high ground-water levels in the valleys, and to maintain treaty-mandated water-quality and quantity requirements of Mexico. The following components in this report, which were identified to be useful in the development of a ground-water management model, are: (1) refinement of the hydrogeologic framework; (2) updated water-level maps, general ground-water flow patterns, and an estimate of the amount of ground water stored in the mound under Yuma Mesa; (3) review and documentation of the ground-water budget calculated by the Bureau of Reclamation, U.S. Department of the Interior (Reclamation); and (4) water-chemistry characterization to identify the spatial distribution of water quality, information on sources and ages of ground water, and information about the productive-interval depths of the aquifer. A refined three-dimensional digital hydrogeologic framework model includes the following hydrogeologic units from bottom to top: (1) the effective hydrologic basement of the basin aquifer, which includes the Pliocene Bouse Formation, Tertiary volcanic and sedimentary rocks, and pre-Tertiary metamorphic and plutonic rocks; (2) undifferentiated lower units to represent the Pliocene transition zone and wedge zone; (3) coarse-gravel unit; (4) lower, middle, and upper basin fill to represent the upper, fine-grained zone between the top of the coarse-gravel unit and the land surface; and (5) clay A and clay B. Data for the refined model includes digital elevation models, borehole lithology data, geophysical data, and structural data to represent the geometry of the hydrogeologic units. The top surface of the coarse-gravel unit, defined by using borehole and geophysical data, varies similarly to terraces resulting from the down cutting of the Colorado River. Clay A is nearly the same as the previous conceptual hydrogeologic model definition (Olmsted and others, 1973), except for a minor westward extension from the city of Yuma. Clay B is extended to the southerly international boundary and increased in areal extent by about two-thirds of the original extent (Olmsted and others, 1973). The other hydrogeologic units generally are the same as in the previous conceptual hydrogeologic model. Before development, the Colorado and Gila Rivers were the sources of nearly all the ground water in the Yuma area through direct infiltration of water from river channels and annual overbank flooding. After construction of upstream reservoirs and clearing and irrigation of the floodplains, the rivers now act as drains for the ground water. Ground-water levels in most of the Yuma area are higher now than they were in predevelopment time. A general gradient of ground-water flow toward the natural discharge area south of the Yuma area still exists, but many other changes in flow are evident. Ground water in Yuma Valley once flowed away from the Colorado River, but now has a component of flow towards the river and Mexicali Valley. A ground-water mound has formed under Yuma Mesa from long-term surface-water irrigation; about 600,000 to 800,000 acre-ft of water are stored in the mound. Ground-water withdrawals adjacent to the southerly international boundary have resulted in water-level declines in that area. The reviewed and documented water budget includes the following components: (1) recharge in irrigated areas, (2) evapotranspiration by irrigated crops and phreatophytes, (3) ground-water return flow to the Colorado River, and (4) ground-water withdrawals (including those in Mexicali Valley). Recharge components were calculated by subtracting the amount of water used by crops from the amount of water delivered. Evapotranspiration rates were calculated on the basis of established methods, thus were appropriate for input to the ground-water flow model developed by the Bureau of Reclamation (William Greer, hydrologist, Bureau of Reclamation, written commun., 2005). Evapotranspiration by crops and phreatophytes were calculated by using crop coefficient methods and meteorological data. Other methods of calculating evapotranspiration rates by using combinations of satellite imagery and ground-based data could be used for higher spatial and temporal resolution. Ground-water return flow during years of low flow on the Colorado River (1972–82, 1987–92, and 1994–96) averaged 79,000 acre-ft per year. Ground-water withdrawal data for 1970–99 were similar to other estimates made by the U.S. Geological Survey for the Yuma area. New water-chemistry data were collected in 12 wells and 8 canals/drains to characterize spatial patterns in chemical constituents, determine isotopic ages of water, infer possible sources of ground water, and locate the vertical intervals of the aquifer that contribute most water to wells. Depth-dependent samples were collected at one of the wells (YM-10). A large quantity of water-quality data were compiled from Bureau of Reclamation and U.S. Geological Survey records and merged into the U.S. Geological Survey National Water Information System database. New samples were analyzed for major ions, nutrients, stable isotopes of oxygen and hydrogen, tritium ( 3 H), and carbon-14 ( 14 C) (along with C 13 /C 12 ratios). Light values of oxygen-18 ( 18 O) and deuterium ( 2 H, D) in well 242-2 indicate recharge from the Colorado River. Heavy water samples from wells 242-22, CADC, and Mesa del Sol indicate local recharge sources. Tritium data indicate there is young water in wells in the valleys and near the edge of Yuma Mesa, while older water is found far from the Colorado River. 14 C data indicate that water from wells near the southerly international boundary is at least several thousand years old.

Arizona, California↗

USGS1996

Water resources of Lincoln County, Wyoming

Streamflow and ground-water quantity and quality data were collected and analyzed, 1993 through 1995, and historical data were compiled to summarize the water resources of Lincoln County.Deposits of Quaternary age, in the valleys of the Bear River and Salt River, had the most well development of any geologic unit in the county.The most productive alluvial aquifers were located in the Bear River Valley and Star Valley with pumping wells discharging up to 2,000 gallons perminute. The ground-water connection between the Overthrust Belt and the Green River Basin is restricted as a result of the folding and faulting that occurred during middle Mesozoic and early Cenozoic time. Total water use in Lincoln County during 1993 was estimated to be 405,000 million gallons. Surface water was the source for 98 percent of the water used in the county. Hydroelectric power generation and irrigation used the largest amounts of water. Dissolved-solids concentrations varied greatly for water samples collected from 35 geologic units inventoried. Dissolved-solids concentrations in all water samples from the LaneyMember of the Green River Formation were greater than the Secondary Maximum Contaminant Level of 500 milligrams per liter established by the U.S. Environmental Protection Agency. Statistical analysis of data collected from wells in the Star Valley monitoring study indicated there was no significant difference between data collected during different seasons, and no correlation between the nitrate concentrations and depth to ground water.

Wyoming↗

USGS1956

Sedimentation and chemical quality of surface waters in the Wind River basin, Wyoming

This report gives results of an investigation by the U. S. Geological Survey of chemical quality of surface waters and sedimentation in the Wind River Basin, Wyo. The sedimentation study was begun in 1946 to determine the quantity of sediment that is transported by the streams in the basin; the probable sources of the sediment; the effect of large irrigation projects on sediment yield, particularly along Fivemile Creek; and the probable specific weight of the sediment when initially deposited in a reservoir. The study of the chemical quality of the water was begun in 1945 to obtain information on the sources, nature, and amounts of dissolved material that is transported by streams and on the suitability of the waters for different uses. Phases of geology and hydrology pertinent to the sedimentation and chemical quality were studied. Results of the investigation through September 30, 1952, and some special studies that were made during the 1953 and 1954 water years are reported. The rocks in the Wind River Basin are granite, schist, and gneiss of Precambrian age and a thick series of sedimentary strata that range in age from Cambrian to Recent. Rocks of Precambrian and Paleozoic age are confined to the mountains, rocks of Mesozoic age crop out along the flank of the Wind River and Owl Creek Mountains and in denuded anticlines in the floor of the basin, and rocks of Tertiary age cover the greater part of the floor of the basin. Deposits of debris from glaciers are in the mountains, and remnants of gravel-capped terraces of Pleistocene age are on the floor of the basin. The lateral extent and depth of alluvial deposits of Recent age along all the streams are highly variable. The climate of the floor of the basin is arid. The foothills probably receive a greater amount of intense rainfall than the areas at lower altitudes. Most precipitation in the Wind River Mountains falls as snow. The foothill sections, in general, are transitional zones between the cold, humid climate of the high mountains and the warmer, drier climate of the basin floor. Average annual runoff in the basin is about 3.6 inches on the basis of adjusted streamflow records for the Bighorn River near Thermopolis. Runoff from the mountains is high and is mostly from melting of snow and from spring and early summer rains. It does not vary greatly from year to year because annual water losses are small in comparison to annual precipitation. In the areas on the floor of the basin, where runoff is low, the runoff is mostly the result of storms in late spring and early summer. The annual water losses nearly equal the annual precipitation; therefore, runoff is extremely variable, in terms of percentage changes, from year to year and from point to point during any 1 year.

Water Supply Paper↗

USGS2022

Hydrogeologic characterization of the San Antonio Creek Valley watershed, Santa Barbara County, California

The San Antonio Creek Valley watershed (SACVW) is located in western Santa Barbara County, about 15 miles south of Santa Maria and 55 miles north of Santa Barbara, California. The SACVW is about 135 square miles and encompasses the San Antonio Creek Valley groundwater basin; the SACVW is separated from adjacent groundwater basins by the Casmalia and Solomon Hills to the north, and the Purisima Hills to the south. At the western, downstream part of the valley, uplifted, consolidated rocks cause groundwater to discharge at land surface at Barka Slough. Since the late 1800s, groundwater has been the primary source of water for agricultural, military, municipal, and domestic uses. Groundwater withdrawal by pumping exceeded the amount of water replenishing the aquifer system during water years 1948–2018, causing groundwater-level declines of more than 150 feet in parts of the valley and reducing base flow at Barka Slough. Reliance on groundwater for agricultural water use (primarily for the irrigation and frost protection of vineyards, and fruit and berry crops) continues to strain the sustainability of the groundwater system. Through a cooperative agreement, the Santa Barbara County Water Agency and Vandenberg Space Force Base invited the U.S. Geological Survey to address declines in groundwater levels, develop a better understanding of the hydrogeologic system, and provide tools to help evaluate and manage the effects of future development of the San Antonio Creek Valley groundwater basin within the encompassing San Antonio Creek Valley watershed (SACVW). The objectives of this study were to (1) refine the hydrogeologic framework of the San Antonio Creek Valley watershed, (2) quantify the hydrologic budget of the valley, and (3) develop hydrologic modeling tools to evaluate and aid in managing the groundwater resource. This report focuses on the first and second objectives to construct a hydrogeologic framework and characterize the historical and present-day hydrologic conditions of the SACVW during water years 1948–2018. As part of the second objective, work included quantifying the hydrologic budget and evaluating the hydrogeologic system using a combination of existing data and geologic and hydrologic data collected for this study. The groundwater-flow system in the SACVW consists of five hydrogeologic units. These separate water-bearing units were identified based on hydrogeologic properties, such as sediment grain size, vertical-head differences in multiple-depth, monitoring-well sites, long-term groundwater level responses to pumping and climate, and the chemical character of groundwater and groundwater age in the mostly semi-consolidated to unconsolidated basin-fill sediments. The hydrogeologic units that comprise the different aquifers vary in their lithologic composition. The upper and lower aquifers (upper Paso Robles Formation, and lower Paso Robles Formation and Careaga Sandstone, respectively) are relatively coarse grained and are comprised of sand, gravel, and clay; the middle confining unit (the middle Paso Robles Formation) is relatively fine grained and is comprised of primarily clay, silt, and sand. The Pezzoni-Casmalia and Los Alamos faults, which are inferred to transect the SACVW between the western and eastern areas of the valley floor, do not appear to substantially affect the groundwater system. Present-day recharge to the study area occurs primarily as infiltration from precipitation and streams in the upland areas of the Casmalia Hills and Solomon Hills, and along the main channel of San Antonio Creek. Reported estimates of annual natural recharge during water years 1948–2018 generally ranged from about 5,000 acre-feet to more than about 30,000 acre-feet. Stable and radioactive isotopes show that groundwater from the lower aquifer is old and probably was recharged as infiltration from precipitation and streams in the eastern upland areas of the Solomon Hills; however, the infiltration and recharge from these sources probably does not occur under present-day climatic conditions. Anthropogenic recharge, from sources such as return flow from agricultural irrigation, municipal water systems, and wastewater effluent, was estimated to range from about 600 acre-feet in 1948 to about 6,600 acre-feet in 2018. The average annual amount of groundwater removed from the SACVW by pumping during 1948–2018 was estimated to be about 17,200 acre-feet per year, increasing from about 3,000 acre-feet in 1948 to about 32,600 acre-feet in 2018. Estimates of annual pumpage generally exceeded estimates of annual recharge beginning in the mid-1970s and continuing through 2018. The predominant direction of groundwater flow under historical and present-day conditions was from the eastern uplands in the Solomon Hills to the west along San Antonio Creek to the discharge area in Barka Slough, and from the northern uplands in the Casmalia Hills south to San Antonio Creek. Pumpage since the early 1900s and the subsequent groundwater-level declines have substantially reduced the amount of natural groundwater discharge at Barka Slough. Estimates of base flow to San Antonio Creek at the western, downstream extent of the SACVW have varied over time in response to changes in groundwater pumpage and climate; however, there was an overall decline in base flow during water years 1956–2018, decreasing from an average of about 1,700 acre-feet per year during 1956–69, to about 300 acre-feet per year during 2016–18. The long-term extraction of groundwater correlates with a decrease in groundwater levels by more than about 150 feet since the early 1940s in the eastern part of the basin near Los Alamos, and as much as about 50 feet in the upland areas and in the western part of the basin. At Barka Slough, groundwater levels have declined below land surface in some places, altering native riparian vegetation in and around the slough. Surface-water quality in the SACVW varied depending on location and the time of year the samples were collected and on the amount of annual precipitation Most groundwater in the SACVW was calcium-bicarbonate-type water with total dissolved-solids concentrations of about 500–800 milligrams per liter generally representing water naturally recharged as infiltration from precipitation and streams. Total dissolved-solids concentrations in some wells ranged from 800 to 8,000 milligrams per liter, suggesting mixing of naturally recharged infiltrated water with water associated with oil-bearing geologic formations, agricultural products, or the evaporation of shallow groundwater. Concentrations of total dissolved solids and the chemical constituents chloride, nitrate plus nitrite (as nitrogen), calcium, and magnesium at selected wells generally increased during water years 1980–2018; increasing concentrations of these constituents may be associated with the expansion of agriculture in the watershed over time and the corresponding increase in the use of nitrates and calcium- and magnesium-based fertilizers and soil additives in modern agricultural practices. The predominant direction of groundwater flow during historical and present-day conditions was from the eastern uplands in the Solomon Hills to the west along San Antonio Creek toward Barka Slough, and from the western uplands in the Casmalia Hills south to San Antonio Creek. The age of groundwater in the SACVW was evaluated using radioactive isotopes, and the flow of groundwater within the SACVW was evaluated using radioactive and stable isotopes. Modern groundwater (recharged after 1952) was generally found adjacent to San Antonio Creek and its tributaries in wells with perforated depths that averaged about 270 feet below land surface. Pre-modern groundwater (recharged before 1952) was found in wells that had average perforation depths of about 540 ft below land surface. Pre-modern groundwater identified in wells in the eastern upland area is interpreted to have had long, slow travel times to the western part of the SACVW where it was eventually discharged as base flow at Barka Slough or extracted as groundwater pumpage.

California↗

USGS1969

Water resources of the Salmon Falls Creek basin, Idaho-Nevada

The northern part of the Salmon Falls Creek basin, referred to as the Salmon Falls tract, contains a large acreage of good agricultural land, but the surface-water supply is inadequate to develop the area fully. Attempts to develop ground water for irrigation have been successful only locally. Specific capacities of wells drilled for irrigation and for test purposes ranged from less than 0.5 to 70 gallons per minute per foot of drawdown. The surface-water supply averages 107,000 acre-feet annually, of which about 76,000 acre-feet is diverted for irrigation. The Idavada Volcanics, the most widespread and oldest water-bearing formation in the Salmon Falls tract, consists of massive, dense, thick flows and blankets of welded silicic tuff with associated fine- to coarse-grained ash, clay, silt, sand, and gravel. Fault zones and jointed rock yield large amounts of water to wells, but massive nonjointed units yield little water. Sand, tuff, and ash beds yield moderate quantities of water. Clay, sandy clay, sand, and pea gravel occur in topographic lows on the Idavada Volcanics. The finegrained sediments yield little water to wells, but the gravel yields moderate quantities. Vesicular porphyritic irregularly jointed olivine basalt flows, which overlie the Idavada Volcanics, underlie almost all the Salmon Falls tract. Lenticular fine-grained sedimentary beds as much as 15 feet thick separate some of the flows. Joints and contacts between flows yield small to moderate amounts of water to wells. Alluvial and windblown deposits blanket most of the tract. Where they occur below the water table, the alluvial deposits yield adequate supplies for stock and domestic wells. Perched water in the alluvium along Deep Creek supplies some stock and domestic wells during most years. Ground-water supplies adequate for domestic and stock use can be obtained everywhere in the tract, but extensive exploration has discovered only five local areas where pumping ground water for irrigation is presently economically feasible. About 8,000 acre-feet was withdrawn for all uses in 1960. Natural discharge of ground water is northward -- toward the Twin Falls South Side Project and the Snake River--and is provisionally estimated to be 115,000 acre-feet annually. Ground water in the Salmon Falls tract has a medium- to high salinity hazard and a low sodium hazard. The salinity does not appear to affect crops presently grown in the tract. The southern part of the Salmon Falls Creek basin, referred to as the upper drainage basin, has little agricultural development and is used mostly for grazing livestock. Silicic volcanic rocks and tuffaceous sedimentary rocks of Tertiary age and alluvial deposits yield water to livestock, domestic, and commercial wells.

Idaho;Nevada↗

USGS1979

Selected water-level records for Oklahoma, 1976-1978

A systematic program to collect water-level records in Oklahoma began in 1937. The objectives of this program are (1) to provide long-term records of water-level fluctuations in representative wells, (2) to facilitate the prediction of water-level trends and indicate future availability of ground-water supplies, and (3) to provide information for use in basic research. Water-level data in table 1 are from wells that are measured annually, prior to the irrigation season, to achieve the most natural representation of the static water level. Water-level measurements listed in the column under 1976 may have been made during December 1975 or January, February, March, April, or May, 1976. Measurements listed in the column 1977 may have been made during December 1976 or January, February, March, or April 1977. Figure 1 shows the counties and number of wells therein, where data were obtained for this report. Records of water levels in Oklahoma are collected through a cooperative program by the U.S. Geological Survey and the Oklahoma Water Resources Board. The records are tabulated and published by the U.S. Geological Survey on an annual basis. The stratigraphic nomenclature and age determinations used in this report are those accepted by the Oklahoma Geological Survey and do not necessarily agree with those of the U.S. Geological Survey except for the Cheyenne Sandstone which is considered to be Purgatoire Sandstone by the Oklahoma Geological Survey (Robert 0. Fay, Personal Communication, August 9, 1979).

Oklahoma↗

USGS1978

The Mississippi River Valley alluvial aquifer in Mississippi

The Mississippi River valley alluvial aquifer, of Quaternary age , contains freshwater in an area of 7,000 sq mi adjacent to the Mississippi River in northwestern Mississippi, and in a 500 sq mi irregular area in southwestern Mississippi. It is the highest yielding aquifer in Mississippi with individual well yields as high as 5,000 gal/min. Major wells producing from the aquifer range in depth from 60 to 260 ft and are commonly screened in the coarse gravel at the base of the aquifer. Water levels in wells are generally between 5 and 30 feet below land surface, except near points of heavy pumping. Water from the alluvial aquifer is a hard, calcium bicarbonate type containing excessive iron in most places. In 1975, 745 Mgal/d, mostly for irrigation, were withdrawn from the alluvial aquifer. In the 7,000 sq mi area in northwestern Mississippi, the alluvial aquifer has been estimated to be capable of yielding over 1,700 Mgal/d, not including the 500 sq mi area in southwestern Mississippi. (Woodard-USGS)

Mississippi↗