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USGS1964

Geology and ground-water resources of the upper Grande Ronde River basin, Union County, Oregon

The upper Grande Ronde River basin is a 1,400-square-mile area in northeastern Oregon, between the Blue Mountains to the west and the Wallowa Mountains to the east. The area is drained by the Grande Ronde River, which flows northeast through this region and is tributary to the Snake River. The climate is generally moderate; temperature extremes recorded at La Grande are 22°F. below zero and 108°F. above. The average annual precipitation ranges from 13 to 20 inches in the Grande Ronde Valley to . more than 35 inches in the mountain highlands surrounding the valley. The topography of. the area is strongly controlled by the geologic structures, principally those related to block faulting. The terrain ranges from the nearly flat floors of the Grande Ronde and Indian Valleys, whose elevations are 2,600 to about 2,750 feet, to the mountainous uplands, whose average elevations are about 5,000 feet and which have local prominences exceeding 6,500 feet. The rocks in the upper Grande Ronde River basin, from oldest to youngest, are metamorphic rocks of pre-Tertiary age; igneous masses of diorite and granodiorite that intruded the metamorphic rocks; tuff-breccia, welded and silicified tuff, and andesite and dacite flows, of Tertiary age; the Columbia River basalt of Miocene and possibly early Pliocene age; fanglomerate and lacustrine deposits of Pliocene and Pleistocene age; and younger deposits . of alluvium, colluvium, and welded tuff. In the graben known as the Grande Ronde Valley, which is the principal populated district in the area, the valley fill deposits are as thick as 2,000 feet. The valley is bordered by the scarps of faults, the largest of which have displacements of more than 4.000 feet. Most of the wells in the area obtain small to moderate supplies of water from unconfined aquifers in the val1ey fill and alluvial fan deposits. Moderate to large quantities of water are obtained from aquifers carrying artesian water in the fan alluvium and the Columbia River basalt. The available supplies of ground water greatly exceed the relatively small amounts that are being used, and the natural supplies are ..adequate for foreseeable domestic, industrial, irrigation, and municipal. requirements. Yields of future wells probably could be improved appreciably over those of present wells by exercising close attention to subsurface conditions during construction, and by greater use of well screens, gravel envelopes, and well development techniques. The chemical quality of the ground water in general is excellent. All waters sampled are potable and are within the desired ranges of hardness and salinity for most public, industrial, and irrigation uses. The average temperature of shallow ground water drawn from, the alluvial fill was 3°F. above the mean annual air temperature. That of water obtained from the basalt is 6°F. above the temperatures computed from the 'normal' gradient of 1.8°F. per 100 feet of increased depth.

Oregon↗
USGS1962

Geology and ground-water resources of the Ahtanum Valley, Yakima County, Washington

The Ahtanum Valley covers an area of about 100 square miles in an important agricultural district in central Yakima County, Wash. Because the area is semiarid, virtually all crops require irrigation. Surface-water supplies are inadequate in most of the area, and ground water is being used increasingly for irrigation. The purpose of this investigation was the collection and interpretation of data, pertaining to ground water in the area as an aid in the proper development and management of the water resources. The occurrence and movement of ground water in the Ahtanum Valley are directly related to the geology. The valley occupies part of a structural trough (Ahtanum-Moxee subbasin) that is underlain by strongly folded flow layers of a thick sequence of the Yakima basalt. The upper part of the basalt sequence interfingers with, and is conformably overlying by, sedimentary rocks of the Ellensburg formation which are as much as 1,000 feet thick. These rocks are in turn overlying unconformably by cemented basalt gravel as much as 400 feet thick. Unconsolidated alluvial sand and gravel, as much as 30 feet thick, form the valley floor. Although ground water occurs in each of the rock units within the area, the Yakima basalt and the unconsolidated alluvium yield about three-fourths of the ground water currently used. Wells in the area range in depth from a few feet to more than 1,200 feet and yield from less than 1 to more than 1,030 gallons per minute. Although water levels in water-table wells usually are shallow--often less than 5 feet below the land surface--levels in deeper wells tapping confined water range from somewhat above the land surface (in flowing wells) to about 200 feet below. Wells drilled into aquifers in the Yakima basalt, the Ellensburg formation, and the cemented gravel usually tap confined water, and at least 12 wells in the area flow or have flowed in the past. Ground-water levels fluctuate principally in response to changes in stream levels, variations in the flow of irrigation ditches and in rates of water application, variations in local precipitation, and seasonal differences in withdrawals from wells. Annual fluctuations of levels generally are less than 10 feet except in localities of heavy pumping. Periodic measurements of water levels in two observation wells in the area indicate, locally at least, a persistent decline in artesian pressures in confined basalt aquifers, although the record is too short to show whether withdrawal by pumping has reached, or is nearing, an optimum balance with recharge. The aquifers are recharged by precipitation, by infiltration from streams, and by ground-water underflow into the area. Ground water is discharged by seepage to streams, by evapotranspiration, by springs and seeps at the land surface, and, artificially, by withdrawal from wells. It is estimated that the seepage discharge to the Yakima River from the area studied may range from about 20,000 to 25,000 acre-feet per year. The consumptive waste of ground water by phreatophytes probably exceeds 4,000 acre-feet per year and may represent a large reclaimable source of water in the area. The annual withdrawal of ground water from wells in the area for domestic, industrial, irrigation, public, and stock supplies is estimated to be 6,300 acre-feet. The chemical quality of the ground water generally is satisfactory for most purposes, although the water from many wells is harder than is desirable for domestic use.

Washington↗
USGS1962

Reconnaissance of ground-water resources in the Western Coal Field Region, Kentucky

In the Western Coal Field region of Kentucky, water is obtained from consolidated sedimentary rocks of Mississippian and Pennsylvanian ages and from unconsolidated sediments of Cenozoic age. Pennsylvanian rocks crop out in more than 95 percent of the area and consist of shale and sandstone interbedded with some limestone and coal. The Pennsylvanian strata are divided into five formations. They are, in ascending order: the Caseyville sandstone and the Tradewater, Carbondale, Lisman, and Henshaw formations. The Anvil Rock sandstone member of the Lisman formation and the Caseyville sandstone are the only bedrock aquifers in the region that are known to yield more than 100 gpm (gallons per minute) to wells. Most bedrock wells produce enough water for a modern domestic supply, more than 500 gpd (gallons per day), and few yield so little water as to be inadequate for hand pumps and bailers, less than 100 gpd. Unconsolidated Cenozoic deposits range from latest Pliocene(?) to Recent in age and consist of clay, silt, sand, and gravel. High gravels, tentatively considered to be late Pliocene and early Pleistacene in age by McFarlan (1950, p. 125), and loess of Pleistocene age are locally exposed, but nearly all of the alluvium is of late Pleistocene and Recent ages. The alluvium along the Ohio River generally yields from a few hundred to as much as 1,000 gpm to single vertical wells and as much as several thousand gallons per minute to wells that have multiple horizontal screens. Alluvium in the tributaries of the Ohio River generally is finer grained than that of the Ohio Valley. The highest known yield from a well in the alluvium of the tributaries is 56 gpm; other wells yield enough for domestic supplies. Availability of ground water in the region depends on the character and thickness of the aquifer penetrated, and, where the aquifer is bedrock on the depth of the water-bearing bed, and to a certain extent on the topographic situation. Most bedrock aquifers in the Western Coal Field region are sandstone and may vary greatly in thickness and composition within short distances. The region is divided into five areas of ground-water availability. Area 1 is confined to the Ohio Valley, most of which is underlain by relatively thick sections of sand and gravel that yield at least 50 gpm to most wells at depths of less than 150 feet. In area 2 most wells yield enough water for a modern domestic supply from depths of less than 300 feet. This area includes the largest part of the bedrock outcrop in the region, some of the alluvial area along the Ohio River, and much of the alluvial areas along the larger tributaries. In area 3 most wells yield enough water from depths of less than 300 feet to supply domestic needs when a hand pump is used. This area covers the bedrock parts of the region that are underlain by shale, sandy shale, and limestone, and the section where few wells are known to yield large supplies of water. In area 4 most wells fail to supply enough water for domestic use from depths of less than 300 feet, probably because they penetrate thick sections of unfractured shale or well-cemented sandstone. In area 5 the yield of wells is unpredictable, commonly because of faulting. The water in the shallow bedrock aquifers of the region is mostly of the sodium bicarbonate or the calcium bicarbonate type. Saline water has been encountered at depths as shallow as 100 feet, but fresh water has been obtained at depths approaching 1,000 feet. Water from the bedrock is soft to moderately hard, but it may contain undesirable amounts of iron. Most water from the alluvium is of the calcium bicarbonate type and is generally harder and contains more iron than water from the bedrock.

Water Supply Paper↗
USGS1964

Geology and ground-water conditions of Clark County, Washington, with a description of a major alluvial aquifer along the Columbia River

This report presents the results of an investigation of the ground-water resources of the populated parts of Clark County. Yields adequate for irrigation can be obtained from wells inmost farmed areas in Clark County, Wash. The total available supply is sufficient for all foreseeable irrigation developments. In a few local areas aquifers are fine-grained, and yields of individual wells are low. An enormous ground-water supply is available from a major alluvial aquifer underlying the flood plain of the Columbia River in the vicinity of Vancouver, Camas, and Washougal, where the aquifer is recharged, in part, by infiltration from the river. Yields of individual wells are large, ranging to as much as 4,000 gpm (gallons per minute). Clark County lies along the western flank of the Cascade Range. in the structural lowland (Willamette-Puget trough) between those mountains and the Coast Ranges to the west. The area covered by the report includes the urban, the suburban, and most of the agricultural lands in the county. These lands lie on a Series of nearly fiat plains and benches which rise steplike from the level of the Columbia River (a few feet above sea level) to about 800 feet above sea level. Clark County is-drained by the Columbia River (the trunk stream of the Pacific Northwest) and its tributaries. The Columbia River forms the southern and western boundaries of the county. Although the climate of the county is considered to be humid, the precipitation ranging from about 37 to more than 110 inches annually in various parts of the county, the unequal seasonal distribution (about 1.5 inches total for ;July and August in the agricultural area) makes irrigation highly desirable for most .crops and essential for some specialized crops. Consolidated rocks of Eocene to Miocene age, chiefly volcanic lava flows and pyroclastics but including some sedimentary strata, crop out in the foothills of the Cascades in the eastern part of the county and underlie the younger, unconsolidated rocks in the lowlands to the west At most places small to moderate quantities of water can be obtained from fractures in the older consolidated rocks. However, in the populated parts of the county, these rocks generally are overlain by considerable thicknesses of more permeable materials, and few wells have been drilled in them. Springs and dug wells yield an ample domestic supply at a number of outlying farms in the foothills. The younger (Pliocene to Recent) unconsolidated materials were deposited chiefly by streams in the basin formed by downwarping of the older rocks. However, some lake deposits and glacial drift also are included. The oldest unit of this group, the lower member of the Troutdale formation of Pliocene age, consists chiefly of clay, silt, and fine sand but includes lenses of coarser sand and, rarely, gravel. The maximum known thickness of the lower member of the Troutdale formation is about 660 feet. This unit is not a good aquifer because most of the strata are fine grained. However, at a few places drilled wells have penetrated lenses of coarser grained materials in these deposits and have obtained small to moderate amounts of water from them. The upper member of the Troutdale formation consists almost entirely of lightly to moderately cemented gravel, of which the most striking feature is the presence of a considerable percentage of quartzite pebbles. The average thickness of the upper member of the Troutdale may originally have been 300 to 400 feet. The member crops out over considerable areas in the county and, where conditions of topography and exposure are optimum, has beer very deeply weathered. It is suggested that the upper member of the Troutdale formation may prove to be of early Pleistocene age.

Washington↗
USGS1961

Effect of reforestation on streamflow in central New York

Hydrologic data have been collected since 1932 in central New York State to determine the effect of reforestation on streamflow. Data are available for three small partly reforested areas and for one nonreforested control area. From 35 to 58 percent of the 3 areas were reforested, mostly with species of pine and spruce. The trees were allowed to grow without thinning or cutting, and by 1958 these reforested areas had developed into dense coniferous woodlots. Intensive statistical analyses of the data from the four study areas were made in 1958. Analyses were made for three hydrologic periods: the dormant season represented by the 6-month period ending April 30, the growing season represented by the 6-month period ending October 31, and the year represented by the 12-month period ending April 30. Analyses of the hydrologic data using multiple correlation with time as a variable and analyses of covariance between early and late periods of record indicated that several significant changes had occurred in the streamflow from the partly reforested study areas. Based on correlation with precipitation, total runoff for the dormant season from the 3 study areas was reduced by annual rates of 0.17 to 0.29 inches per year. Based on correlations with streamflow from a control area, total runoff from the partly reforested Shackham Brook area was reduced by average rates of 0.14 inches per growing season, 0.23 inches per dormant season, and 0.36 inches per hydrologic year. Peak discharges on Shackham Brook during the dormant season were reduced by 1958 by an average of 41 percent for the season, with reductions ranging from an average of 66 percent for November to an average of 16 percent for April. No significant changes were found in the peak discharges for the growing season, rates of base-flow recession, volumes of direct runoff, or annual low flows of streams in the three partly reforested areas. The significant reductions in total runoff are attributed to increases in interception and transpiration in the reforested areas. The reductions in peak discharges during the dormant period are attributed largely to increased interception and sublimation of snowfall, and a gradual desynchronization of snowmelt runoff from the wooded and open areas of partly reforested watersheds. The changes in streamflow occurred gradually over the years; it could not be determined from the data whether changes in streamflow were still occurring in 1958, or whether they had reached a maximum.

Water Supply Paper↗
USGS1963

Geology and ground-water resources of Montgomery County, Alabama

Montgomery County includes an area of 790 square miles in east-central Alabama. The economy of Montgomery County is related primarily to the growing and processing of agricultural products. The county is in the northern part of the Coastal Plain. It consists of parts of four divisions of the Coastal Plain: the terraces, the Black Prairie, the Chunnennuggee Hills, and the flood plains. The county drains north and northwest into the Alabama and Tallapoosa Rivers, except for a small area in the southern part of the county that is drained by tributaries of the Conecuh River. Sedimentary rocks of Late Cretaceous age underlie Montgomery County. They are divided, in ascending order, into the following: Coker and Gordo formations of the Tuscaloosa group; Eutaw formation; and Mooreville and Demopolis chalks, Ripley formation, Prairie Bluff chalk, and Providence sand of the Selma group. The Clayton formation of Tertiary age crops out in a small area in the southern part of the county. Pleistocene terrace deposits of the ancestral Alabama River overlie the older rocks in the northern part of the county. Recent alluvium underlies the flood plains of the larger streams. The Cretaceous and younger rocks consist chiefly of clay, chalk, sandstone, sand, and gravel, and a few thin beds of limestone. These deposits are underlain by a basement complex of pre-Cretaceous crystalline rocks. Large-scale withdrawals of water began in the Montgomery area about 1885. Pumpage by the city of Montgomery in 1958 averaged about 15 million gallons per day. It is estimated that an additional 10 to 15 million gallons per day was pumped in the county for industrial, irrigation, domestic, and stock use. The principal aquifer in the country is the Eutaw formation. It supplies water to the city of Montgomery municipal wells, to industrial wells in the Montgomery area, and to most domestic and stock wells in the northern two-thirds of the county. Irrigation wells also tap the Eutaw. Yields from wells range from 350 to 600 gallons per minute. The Gordo formation, the upper part of the Coker formation, and the Pleistocene terrace deposits in the Montgomery area also yield moderate to large quantities of water to municipal and industrial wells. The lower part of the Coker formation is not developed as a source of water supply, but information obtained during the investigation rthat led to this report indicates that it may be a potential source of water to wells of large capacity. Sand beds in the Ripley formation, Providence sand, and Recent alluvium in -the southern part of the county yield adequate amounts of water to domestic and stock wells. Most of the ground water used in Montgomery County occurs under artesian conditions, although water-table conditions occur in the Pleistocene terrace deposits and Recent alluvium, and in the outcrop areas of the Eutaw and Eipley formations and the Providence sand. Most of the water recharging the Ooker, Gordo, and Eutaw formations in their areas of outcrop also is discharged in these areas; only a small quantity of water moves downdip beneath the overlying chalk beds. The natural discharge, and hence the natural recharge, is estimated to be 0.2 to 0.3 million gallons per day per square mile of outcrop. All ground water in the county is of chemical quality that is satisfactory for most uses, although locally it is high in iron or chloride content and is hard. Water from the Eutaw formation a few miles southwest of Montgomery's West well field is very high in chloride content. This water moves toward the cone of depression in the piezometric surface produced by pumping in the West well field. Much additional ground water could be pumped from the Eutaw formation, especially south of Montgomery's West well field. Additional water also is available from the upper part of the Coker formation. Before large groundwater developments are planned, however, the problems of well spacing and pumping rates should be studied in order to determine the maximum development permitted by the supply. Observation wells should be installed in the Eutaw formation southwest of Montgomery's West well field to detect encroachment of water of high chloride content from adjacent Lowndes County.

Alabama↗
USGS1964

Ground water in folded Cretaceous sandstone of the Bhachau area, Kutch, India, with reference to the Kandla Port water supply

This report is based on an investigation of the availability of ground-water supplies in the Bhachau area for the nearby Kandla Port and township development undertaken by the Government of India. This seaport lies on an estuary of the Gulf of Kutch in western India and in the eastern part of the State of Kutch. The fieldwork on the investigation was carried on from November 1952 through April 1953 with continuing hydrologic observations through 1954-55. The fieldwork included: geologic mapping and delimitation of the principal aquifers of the region; preparation of water-table maps; a detailed inventory of existing wells and springs; observations of significant water table fluctuations; preparation of isobicarb, isochlor and isosulf maps to show the areal distribution of ground-water salinity. The Bhachau area includes about 116 square miles in eastern Kutch and lies in a belt of semiarid low-latitude steppes. The mean annual rainfall is about 15 inches, most of which falls from late June to late September during the southwest monsoon. The area includes a central sandy upland ranging from about 100 to 250 feet above sea level ; a northern lowland of between about 50 to 125 feet altitude that slopes north to the Great Rann of Kutch; a belt of low buttes and discontinuous ridges ranging from about 200 to 275 feet above sea level; and southern lowland which slopes in a southerly to southeasterly direction from an altitude of about 125 feet to 25 feet or less near the Gulf of Kutch. The principal streams are Kageshwar Vokra and Kara Vokra which drain north to the Great Rann and Kotwala Vokra and Dalwala Vokra which drain south toward the Gulf of Kutch. The rocks of the Bhachau area include nonmarine and marine sediments of Mesozoic, Tertiary, and Quaternary age and volcanic rocks of late Mesozoic to early Tertiary age. The oldest rocks in the area are medium- to coarse-grained white to buff current-bedded friable sandstone with occasional partings of white silty shale of the Upper Bhuj series that has been assigned to the Early Cretaceous. The soft friable sandstone of the Upper Bhuj series constitutes the most productive ground-water reservoir in the Bhachau area. At present (1955) there are nine irrigated tracts for which water is obtained from dug wells less than 90 feet deep in the Upper Bhuj. These wells are worked by bullocks and 'motes' (leather bags) at withdrawal rates ranging from about 6,000 to 24,000imperial gallons per day; however, many existing individual wells if equipped with mechanical pumps are capable of yielding 100,000 gallons per day. The Deccan trap of Late Cretaceous to Eocene age occurs in a sequence of basaltic lava flows in the Bhachau area, but trap dikes, sills and plugs that are common in other parts of Kutch have not been observed in the area. Laterite of probable Eocene age is extensive at the top of the Deccan trap, and in places where the lava flows are thin the parent rock has been almost completely lateritized. The Deccan lava flows or the laterite, where the trap is absent, rest disconformably on the Upper Bhuj. No wells have been observed in the Deccan trap of the Bhachau area, but it is possible that locally small supplies of good water may be obtained from these rocks. The Tertiary sediments, which are assigned to the Manchhar series of Pliocene age, generally rest on the laterite or the Deccan trap ; but where both are absent, the Manchhar rests directly on the Upper Bhuj. The Manchhar series includes massive reddish-brown gypseous clay shales, laminated gray siltstones, some limestone, mottled sandstone, and laterite trap gravel. Only meager supplies of brackish water are obtained from wells in these sediments. Along the channels of Kotwala, Dalwala, Kageshwar, and Kara Vokras are narrow bands of unconsolidated coarse sand with fine gravel of Quaternary age. No wells were observed in these deposits, but it is possible that locally they may contain small supplies of bracki

Water Supply Paper↗
USGS1964

Artesian water in the Malabar coastal plain of southern Kerala, India

The present report is based on a geological and hydrological reconnaissance during 1954 of the Malabar Coastal Plain and adjacent island area of southern Kerala to evaluate the availability of ground water for coastal villages and municipalities and associated industries and the potentialities for future development. The work was done in cooperation with the Geological Survey of India and under the auspices of the U.S. Technical Cooperation Mission to India. The State of Kerala, which lies near the southern tip of India and along the eastern shore of the Caspian Sea, contains a total area of 14,937 square miles. The eastern part of the state is s rugged mountainous highland which attains altitudes of more than 6,000 feet. This highland descends westward through piedmont upland to s narrow coastal plain, which reaches a maximum width of about 16 miles in the latitude of Shertalli. A tropical monsoon rain-forest climate prevails in most of Kerala, and annual rainfall ranges from 65 to 130 inches in the southern part of the coastal plain to as much a 200 inches in the highland. The highland and piedmont upland tracts of Kerala are underlain by Precambrian meamorphic and igneous rocks belonging in large parabola-the so-called Charnockite Series. Beneath ahe coastal plain are semiconsolidated asunconsolidated sedimentary deposits whose age ranges from Miocene to Recent. These deposits include sofa sandstone and clay shale containing some marl or limestone and sand, and clay and pea containing some gravel. The sofa sandstone, sand, and gravel beds constitute important aquifers a depths ranging from a few tens of feet to 400 feet or more below the land surface. The shallow ground war is under water-able or unconfined conditions, but the deeper aquifers contain water under artesian pressure. Near the coast, drilled wells tapping the deeper aquifers commonly flow with artesian heads as much as 10 to 12 feet above the land surface. The draft from existing wells in the coastal belt between Quilon and Alleppy was estimated at 1 to 1 1/2 million imperial gallons a day. However, favorable conations exist for considerable further ground-water development in the coastal plain provided that sufficient attention is given to the potential hazards of saltwater encroachment and local overdevelopment. It is estimated that the overall potential for development of water from wells is probably at least several tens of millions of gallons a day, and perhaps more, in the Malabar Coastal Plain of southern Kera. Such a draft would have to be well dispersed to avoid overdevelopment and salt-war encroachment.

Water Supply Paper↗
USGS1964

Hydrogeologic reconnaissance of Poro Point and vicinity, Luzon Island, Philippines

In 1961 a reconnaissance of the geology and ground-water hydrology of Poro Point, on the west coast of Luzon Island, Philippines, was made on behalf of the U.S. Department of the Navy. Poro Point, which marks the northern end of Lingayen Gulf, is about half a mile wide and projects northwestward about 2 miles into the China Sea. The point is underlain by coralline limestone of probable Pleistocene age. The aquifer system consists of a fresh-water lens floating on salt water within the coralline limestone. Several tube wells obtain fresh water from the lens, but in May, at the end of the 6-month dry season during which rainfall totals only 40 inches, the water becomes brackish. 'Skimming wells' are considered the best method of obtaining fresh water from the lens, whose annual range in average thickness is probably 25 to 40 feet. Recharge is about 2,000-3,000 acre-feet per year and is derived wholly from precipitation during the 6-month wet season in which rainfall totals about 92 inches. The approximate amount of ground water stored in the fresh-water lens ranges from about 3,000 acre-feet at the end of the dry season to about 5,000 acre-feet at the end of the wet season. Most of the ground water is discharged through seeps and submarine springs around Poro Point; pumpage in 1961 was only about 100 acre-feet.

Water Supply Paper↗
USGS1977

Ground-water resources of Cambodia

Cambodia (now the Khmer Republic), in tropical, humid southeast Asia, has an area of 175,630 km and a population of about 5 million. The Mekong River, one of the world's largest rivers, flows through Cambodia. Also, the Tonle Sap (Grand Lac), a highly productive fresh-water lake, functions as a huge off-channel storage reservoir for flood flow of the Mekong River. Surfacewater discharge in streams and rivers of Cambodia is abundant during the wet season, mid-May through mid-November, when 85 percent of the precipitation falls, but is frequently deficient during the remainder of the year. Annual rainfall ranges from 1,370 mm in the central lowlands to more than 5,000 mm in the mountainous highlands. The mean annual temperature for the country is 27.5?C and the evaporation rate is high. During 1960-63, 1,103 holes were drilled in 16 of the 18 khets (provinces), of which 795 or approximately 72 percent, were productive wells at rates ranging from 1.1 to 2,967 l/min. The productive wells ranged in depth from 2 to 209.4 m and were 23.2 m deep on the average. Mr. Rasmussen ' studied the subsurface geology of Cambodia in considerable detail by examining drillers' logs and constructing nine geologic cross sections. The principal aquifer tapped by drilled wells in Cambodia is the Old Alluvium. In many places, however, dug wells and a few shallow drilled wells obtain water from the Young Alluvium. Sandstone of the Indosinias Formation yields moderate to small quantities of water to wells in a number of places. Also, wells tapping water-bearing basalt have a small to moderate yield. The quality of water is recorded in only a few analyses. The dissolved solids concentrations appear to be generally low so that the water is usable for most purposes without treatment. Some well waters, however, are high in iron and would have to be aerated and filtered before use. In this report, well records are tabulated, and the geology and hydrology is discussed by khets. The bulk of the available information is on the central lowlands and contiguous low plateaus, as the mountainous areas on the west and the high plateaus on the east are relatively unexplored with respect to their ground-water availability. No persistent artesian aquifer has been identified nor have any large potential ground-water sources been found .although much of the country yet remains to be explored by test drilling. Well irrigation for garden produce is feasible on a modest scale in many localities throughout Cambodia. It does not seem likely, however, that large-scale irrigation from wells will come about in the future. Ground water may be regarded as a widely available supplemental source to surface water for domestic, small-scale industrial, and irrigation use.

Water Supply Paper↗
USGS1976

Hydrologic evaluation of salinity control and reclamation projects in the Indus Plain, Pakistan--A summary

This report summarizes the observations and findings of a team of four specialists from the U.S. Geological Survey assigned to Pakistan under the auspices of the U.S. Agency for International Development during May to August 1972 for a hydrologic evaluation of Salinity Control and Reclamation Projects in the Indus Plain Individual members of the team undertook comprehensive studies related to climatology, surface-water hydrology, and the canal system; streamflow and sediment yields of the rivers; computer applications to hydrologic data; aquifer characteristics; hydrologic evaluation of Salinity Control and Reclamation Projects (SCARPs); tubewell performance; hydrology of shallow versus deep tubewells; well and well-screen design in the Indus Plain; evaluation of observed and anticipated trends in both private and public tubewell development; evaluation of water-quality programs, data analysis, and records, and computer coding of special water-quality data; and evaluation of water-level data, well discharge and specific-capacity tests and aquifer tests. The reclamation program, by pumping from tubewells, has been notably successful in lowering the water table, in providing supplemental water for irrigation and for leaching of salinized soils, and in improving crop production. Some changes in water quality have been observed in SCARP-I and the Mona Scheme of SCARP-II, but these have not as yet (1972) significantly affected the utility of the water for irrigation. Problems associated with reclamation include control of deterioration in performance of tubewells and their rehabilitation, local brackish or saline-water encroachment, and maintenance of a favorable salt balance in the ground-water system. Rapid and as yet (1972) unregulated growth of shallow private tubewell development in the past decade has introduced complicating factors to the reclamation planning of the early 1960's which had emphasized public tubewell development through the SCARP program. In comparing shallow (0-200 feet) with deep (200-400 feet} tubewell development, it is concluded that long-term response of the water table is the same, whether many shallow wells of small capacity or fewer deeper wells of large capacity pump the same total volume of water in the same area. Moreover, it is concluded that there is no definite advantage for either type of pumping regime with respect to water quality. Utilization of the Punjab aquifer could be greatly enhanced by recharge of high-quality water diverted from the Chenab and Jhelum Rivers to the Ravi and Sutlej Rivers by way of the link and irrigation canals during periods of surplus flow. Recharge to the aquifer could also be improved by diversion of high-quality water from the Chenab and the Jhelum to natural nalas and other surface drainageways during periods of surplus flow. Such recharge would be of much better quality than water leaching downward from irrigated fields. Continued monitoring of the hydrologic system and research on problems engendered by reclamation are essential to the viability of the SCARP program and related water-resources development in the Indus River Basin.

Water Supply Paper↗
USGS1962

Ground-water resources of Camas Prairie, Camas and Elmore Counties, Idaho

Camas Prairie is an eastward-trending intermontane basin along the north flank of the Snake River Plain in southern Idaho. The basin is about 40 miles long and averages about 8 miles wide. It was formed as a structural depression in which a considerable thickness of alluvial and lake deposits accumulated behind basalt flows, which at times blocked the outlet to the east. Intrusive and extrusive rocks of Cretaceous to Quarternary age enclose the basin on the north, west, and east. The enclosing rocks yield small amounts of water to springs and wells from the weathered mantle and fractures. The principal aquifers are sand and gravel in the alluvial fill, and basalt. Water in the shallow deposits is not confined, and the water table generally is less than 10 feet below the surface at most places. Ground water in the deeper deposits occurs chiefly in two horizons that comprise the upper and lower artesian aquifers. Throughout much of the prairie, the pressure is sufficient that water will flow from wells in these aquifers. Recharge to the basin is from direct precipitation and percolation of stream runoff from the bordering mountains. Ground water moves from the higher areas at the base of the encircling mountains toward the center of the basin and the eastern outlet. The artesian aquifers leak by upward percolation through the imperfectly confining beds and help maintain the shallow water table. Basalt, which interfingers with the alluvial deposits, is an important aquifer near the southeast margin of the prairie and at the east end. Annual recharge to the artesian aquifers is estimated to be about 40,000 acre-feet. Discharge from the artesian aquifers is about equally divided between upward leakage to the shallow aquifers and underflow out of the prairie. Most of the underflow discharges into Camas Creek or Magic Reservoir east of the prairie; little of the underflow reaches the Snake River Plain. Wells drilled for irrigation generally yield 500 to 1,200 gallons per minute from the artesian aquifers. Better construction and development methods would result in considerably better yields. Wells drilled in the basalt will yield 2,000 to 3,000 gallons per minute with moderate drawdowns. Computations made using aquifer coefficients, estimated on the basis of data collected during the investigation, suggest that 12,000 acre-feet of ground water might be withdrawn annually. However, the aquifers are limited in areal extent, and productivity of the alluvial aquifers is not great. Consequently heavy development would result in large drawdowns in wells, and there would be much interference between wells. The postulated large withdrawals from wells on the prairie would be supplied in part by a reduction in underflow from the prairie and in part by a decrease in leakage from the artesian aquifers, which in turn would cause a decline in the shallow water table.

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