USGS Publications Warehouse

Abstract

Ground water in the United States has emerged from a quantitatively minor (though incalculably valuable) water source, whose chief role was in the settlement of primitive areas, to a major source now accounting for one-fifth to one-sixth of the Nation's total withdrawal requirements for water. With the growth in ground-water withdrawals is an accompanying growth in the realization that large-scale development of ground water is feasible only on the basis of a fuller understanding than has existed to date of the complex interrelations of the hydrologic cycle and of ground water's place in the cycle. This report outlines briefly the principles of water occurrence and describes the water situation in the United States as of 1960-61, with emphasis on the occurrence of ground water and the status of development and accompanying problems. The Nation has been divided into 10 major ground-water regions by H. E. Thomas (1952). The report summarizes the occurrence and development of ground water in each of Thomas' regions. In a large terminal section it also describes the occurrence and development of water, again with emphasis on ground water, in each of the 50 States and in certain other areas. The main text ends with a discussion of the-water situation and prospects of the Nation, and of the role to be played by ground water in meeting future needs. The 10 ground-water regions, in the order listed by Thomas and followed here, are the Western Mountain Ranges, the Alluvial Basins (Thomas' Arid Basins), the Columbia Lava Plateau, the Colorado Plateaus and Wyoming Basin (Thomas' Colorado Plateau), the High Plains (Thomas' Great Plains), the Unglaciated and Glaciated Central regions, the Unglaciated and Glaciated Appalachian regions, and the Atlantic and Gulf Coastal Plain. The Western Mountain Ranges include the northern Coast Ranges, the Cascade Range and Sierra Nevada, the isolated ranges of the Basin and Range province, and the Rocky Mountains. They are the West's precipitation-catching and water-shedding highlands, serving as the major sources of water for the vast 'have not' area surrounding them. Built largely of dense, relatively impermeable rocks, they are largely unfavorable for the occurrence of ground water. As defined, however, they include a few sizable bodies of alluvium and permeable bedrock, as well as weathered rock and fractures in unweathered rock, which absorb, store, and transmit ground water. Their relatively small water needs generally are met readily from streams, springs, or wells, and they have a large surplus of water for export to the adjacent drier lowlands. The Alluvial Basins include the alluvial lowlands of the Basin and Range province and of the southern and larger part of coastal California. As defined they include a separate area, the alluvial lowland of the Puget-Willamette trough between the Coast Ranges and the Cascade Range in Oregon and Washington. At the northwest end of the main body of the region they overlap with the Columbia Lava Plateau in an area in which block-fault mountains of volcanic rocks alternate with alluvial basins. On the southeast they overlap similarly with the Unglaciated Central region. The Alluvial Basins include areas of water-bearing alluvium which constitute the principal residential, agricultural, and industrial sites of the Southwest. They have an enormous present water demand, and a still greater potential demand by virtue of their current rapid population growth and of the presence of fertile land in amounts greatly exceeding that which currently is irrigated or conceivably could be supplied with water. The region accounts for a large share of the Nation's existing and potential water problems. Available streamflow, which serves both as a direct source of water and as the chief source of ground-water recharge, is largely appropriated. Ground water is withdrawn on a large scale, in many parts of the region at rates far in excess of replenishment. Problems of soil erosion and sedimentation of streams and reservoirs are widespread. The chemical quality of water is naturally poor in large parts of the region and is becoming or may become so in other parts as a result of continued withdrawal and use of water. Methods for alleviating the water situation include development of the region's remaining potential surface- and ground-water supply; reduction of avoidable waste including excessive irrigation applications, salvage of water transpired by low-value phreatophytes, and reduction of evaporation from reservoirs; improved waste treatment and increased reuse of water; increases in runoff by watershed management; increases in precipitation by weather modification, to the extent feasible; and conversion of irrigated land to other uses returning more dollars per acre-foot of water. A large share of the Nation's water-resource effort will have to be devoted to this region. The Columbia Lava Plateau is a rather high, rather dry area between the Cascade Range and the Rocky Mountains, underlain by volcanic rocks which are largely rather permeable basalt and which are interbedded with or overlain by unconsolidated sediments both permeable and impermeable. The region is traversed by large streams draining the adjacent mountains, and some of its plateaus are high enough to receive substantial precipitation themselves. The large water supply in the streams and water-bearing rocks is developed on a major scale for irrigation. The region has large remaining potentialities for water-resource development if the intimate relation between streams and aquifers is taken fully into account and if problems of competition--such as between irrigation and hydropower generation--can be resolved. The Colorado Plateaus and Wyoming Basin lie mainly between the Great Basin section of the Basin and Range province and the Rocky Mountains. The region consists mainly of high, dry, dissected plateaus underlain by sedimentary rocks, principally shale and sandstone. It is drained mainly by the Colorado River and its tributaries. In both surface water and ground water, it compares unfavorably with the Columbia Lava Plateau. Irrigation is relatively unimportant, and in large areas even domestic and stock water is difficult or expensive to get. The region has valuable industrial assets in its oil and gas, oil shale, coal, uranium, potash, and other mineral deposits. Water is the key to the future of the region, and full development of the surface water and exploration for and full development of the ground water will be essential. The High Plains ground-water region coincides approximately with the High Plains section of the Great Plains physiographic province. It lies east of, but in most of its extent is separated by scores of miles from, the Rocky Mountains in the stretch from Nebraska and southeastern Wyoming on the north to the High Plains of Texas and adjacent New Mexico on the south. It is the remnant of a formerly continuous alluvial plain stretching from the Rocky Mountains and the chain of block-fault mountains on the south to--and in places perhaps beyond--the eastern parts of Nebraska, Kansas, Oklahoma, and Texas. The alluvium, known in general as the Ogallala Formation, is largely permeable and yields hundreds of gallons per minute to many thousand wells, used largely for irrigation but meeting also most needs for municipal and industrial supply. The High Plains region is crossed by several large streams that head in the Rockies, and their water is largely appropriated for irrigation within and downstream from the boundaries of the region. Except in a few places along these streams, the recharge of the Ogallala Formation is derived entirely from local precipitation. The recharge from precipitation is generally small, an inch of water per year or less (in large areas much less), except in areas where the surficial sediments are sandy. Small sandy areas are scattered throughout the region, but by far the largest sandy area is in central Nebraska, where dune sand covering hundreds of square miles absorbs nearly all the precipitation and transmits it to the water table in amounts ranging from 1 to as much as 5 inches per year. Pumping of ground water is greatest in the southern High Plains of Texas but is growing rapidly in other parts of the High Plains region except the Sand Hills of Nebraska. Recharge is still being balanced by natural discharge at the edges of the plains, which has not yet been affected by the pumping. Thus, virtually all the water pumped, in effect, is coming out of storage. The disparity is most marked in the southern High Plains of Texas, where the withdrawal in recent years has been about 5 million acre-feet per year and the recharge is perhaps 50,000 to 75,000 acre-feet per year. In such areas the withdrawal inevitably must decrease as storage is reduced, yields of wells fall off, and pumping becomes more expensive or--at current rates--impossible. Surface water is not available to meet any substantial fraction of the current ground-water demand. In all the High Plains except the Sand Hills of Nebraska, the same decisions will ultimately have to be made as are now facing Texas; even in the Sand Hills, downstream water rights on streams fed by seepage from the sand must be considered. The Unglaciated Central region is a large area of Paleozoic, Mesozoic, and early Cenozoic sedimentary rocks in the middle of the United States. Except for the High Plains it includes the area between the Rocky Mountains on the west and the Appalachian Highlands on the east, and between the glaciated part of the country on the north and the Gulf Coastal Plain on the south. The region narrows to about 20 miles in southern Illinois where the upper Mississippi Embayment of the Coastal Plain extends into the southernmost part of that State, then widens again. By definition the region includes a separate area in southwestern Wisconsin and immediately adjacent area--a part of the so-called Wisconsin Driftless section. The region has a wide range in climate but in greatest part is characterized by only small to moderate ground-water supplies in the bedrock strata and by saline ground water at depths more than a few tens to a few hundreds of feet below local stream level. In a few sizable areas, especially the Ozark region in southern Missouri and adjacent area. the Roswell artesian basin in New Mexico, and the Edwards Plateau and adjacent Balcones fault zone in Texas, the rocks are more permeable than the average and carry large quantities of ground water. In the three areas the principal water-bearing rocks are limestone and dolomite (carbonate rocks). In a few other areas, including the Powder River Basin in northeastern Wyoming and belts in Texas, Oklahoma, and Kansas, sandstone yields more water than average for the region. In a belt in the Appalachian Plateaus extending from northwestern Alabama to Ohio, both sandstone and carbonate rocks carry water. 'Watercourses'--strips of permeable alluvium along perennial streams--are productive sources, especially along certain stretches of the Ohio, Missouri, Arkansas, and Red Rivers that are within the region. The region is moderately to heavily populated, farmed, and industrialized, and ground water is developed widely for rural domestic and stock, municipal, and industrial supply and locally for irrigation. In spite of the high proportion of the area in which ground-water supplies are not abundant, ground water has a considerable remaining potential. The Glaciated Central region to the north is generally similar to the Unglaciated Central region in climate, cultural development, and bedrock water supplies but differs from it by the presence of a mantle of glacial drift which covers the bedrock and contains many productive sand and gravel aquifers. Watercourses in which the alluvium is largely giacial outwash traverse the region in many places, including stretches of the Ohio and Missouri Rivers that lie within the region as defined. The two Central regions contain a considerable proportion of the Nation's productive farmland. Irrigation is not widespread in either region, but full-scale irrigation with both surface and ground water is large or growing in the western parts, and supplemental irrigation with water from both streams and wells is growing in the central and eastern parts. As in the Unglaciated Central region, there is widespread use of ground water in the Glaciated Central region for rural, municipal, and industrial supply. The glacial drift is most productive in the middle part of the region--that is, in eastern and southern Minnesota; all except the 'Driftless' area of Wisconsin and locally, in the form of glacial outwash from the adjacent area, even there; in much of the Southern Peninsula of Michigan and the northern two-thirds of Indiana; and in other, smaller areas elsewhere. Important bedrock aquifers include sandstone strata of Cambrian and Ordovician age and associated carbonate rocks in southern Minnesota and Wisconsin, northeastern Iowa, and northern Illinois; sandstone strata in parts of the Southern Peninsula of Michigan; and alternating carbonate-rock and sandstone strata in the eastern part of the Northern Peninsula of Michigan and part of the Southern Peninsula and in northern and eastern Indiana and western Ohio. Although, as in the Unglaciated Central region, ground water is locally scarce or overdeveloped, the region has a large remaining potential if supplies are located, evaluated, and developed properly. In both the Glaciated and the Unglaciated Central regions, both ground water and surface water in general are least adequate in the western, drier parts, and much of the future effort to secure water supplies will have to be exerted there. The Unglaciated Appalachian region includes the unglaciated parts of the eastern and higher part of the Appalachian Plateaus province and the unglaciated parts of the Valley and Ridge, Blue Ridge, and Piedmont provinces. The four provinces represented are rather different in types of rocks and geologic structure, but in all of them ground water is abundant only locally. The least productive part is the Blue Ridge, built of dense, sparsely fractured, rather impermeable crystalline rocks that yield little water to wells but give rise to many small springs, whose supply is rather well sustained because of abundant, well-distributed precipitation. The Piedmont is underlain by similar rocks, but a thick mantle of weathered rock overlies the fresh rock except in young, deep gorges: and the zone of fractures below the mantle has not been thinned or removed by erosion to the extent that it has in the Blue Ridge. Hence, the Piedmont is more favorable for the occurrence of ground water in at least small quantities; also, belts of sandstone and shale of Triassic age in downfaulted basins form ground-water areas that in general are reasonably productive. The Valley and Ridge province includes some productive areas of cavernous water-bearing limestone. The cavernous zones are erratic, but they can be pinpointed by detailed study and test drilling. The part of the Appalachian Plateaus province within the region is generally unfavorable for ground water except for small supplies. The chief waterbearing rocks are sandstone, but there are some rather productive carbonate-rock aquifers, especially in the southern part. The province is rather rugged and streams are flashy, so that surface water also is not abundant unless artificial storage can be provided. In the region as a whole the precipitation is generally ample for crop growth; rural domestic and stock needs for water are rather readily met from wells and springs, and municipal and industrial supplies are obtained from streams and reservoirs or, in favorable areas, from wells. Thus problems of water supply generally are not critical, except when to develop an adequate supply proves to be beyond the economic capability of the person, company, or municipality needing the water. Floods, erosion, and pollution are problems in substantial areas. The Glaciated Appalachian region is a generally well-watered area but one of heavy population and industrial development and many problems of local inadequacy or pollution of water. It includes all New England, eastern New York, east-central Pennsylvania, and northern New Jersey. The most productive bedrock aquifers are sandstone in part of northern New Jersey and sandstone and carbonate rocks in scattered areas in New York and adjacent New England. The best aquifers, however, are sand and gravel of stratified glacial drift, chiefly along some stretches of the principal streams and in scattered interstream areas. Ground water meets most rural domestic and stock needs but except in a few areas is in an early stage of development for larger scale uses. Surface water, which is abundant, meets most large-scale demands for municipal and industrial use. There is little irrigation at present. Stream pollution is perhaps the most serious water-related problem. There is some competition between use of streams for hydropower generation and that for water supply. The region as a whole has a large water-resource potential in its surface water and, in a small proportion of the total area, its ground water. The Atlantic and Gulf Coastal Plain is a large and productive region stretching from Cape Cod and offshore islands in Massachusetts to the Rio Grande in southernmost Texas and extending northward in the Mississippi Embayment to southernmost Illinois and adjacent westernmost Kentucky and southeasternmost Missouri. It is underlain by a seaward-thickening wedge of strata of gravel, sand, silt, clay, marl, and limestone of Cretaceous and later age that includes many productive aquifers. Owing to the nearness of the Atlantic Ocean and Gulf of Mexico, precipitation is generous. And, across the region flow the streams that drain the most of the Nation east of the Continental Divide. The region thus has enormous resources of both surface water and ground water. The chief aquifers in most of the region are sand or sand and gravel, including productive glacial outwash in Long Island and adjacent area and alluvium along many watercourses especially in the Mississippi Embayment. The thickness of Coastal Plain strata at the coastline ranges from a few hundred feet in the northeast to perhaps 40,000 feet in southern Louisiana. and the depth of fresh water from the same few hundred feet or less to as much as 6,000 feet in one area in Texas, Consolidated-rock aquifers include highly productive limestone and dolomite nearly throughout Florida and in adjacent Georgia and South Carolina. Ground-water development is locally heavy, including withdrawals of tens of millions of gallons per day for single cities and industries and heavy pumping for irrigation in Florida, the Yazoo Delta in Mississippi, the Grand Prairie region of Arkansas, and the eastern Texas Coastal Plain. The principal limit on ground-water development is imposed by existing or potential encroachment-of salt water from the coast or from the downdip extensions of aquifers all along the coast and along bodies of tidewater indenting the coastline; nevertheless, fresh artesian water extends all the way to and beyond the coast in substantial stretches. The region has very large potentialities for additional development of both ground water and surface water, provided that water supplies are studied and evaluated thoroughly and developed intelligently. Alaska and Hawaii differ greatly in geology and climate but are similar in having wide ranges in ground-water availability. In Alaska the main problems are. the presence of permafrost, which may inhibit or prevent the development of ground water, and the lack of productive aquifers in certain areas. In Hawaii the principal factors limiting development are the possibility of saltwater encroachment and the paucity of recharge in dry leeward areas. Both States have large overall water resources and considerable potential for additional development in favorable areas. The water resources of Oahu are gradually approaching full development. , Puerto Rico has large ground-water supplies in certain areas and a substantial total water supply, but economic factors will make full development of the water, resources difficult. The nearby Virgin Islands and island possessions of Puerto Rico are much drier and have only very small supplies of water. St. Croix and Vieques are the largest of the American islands and have the largest water supplies, but storage of surface water and development of ground water will have to be supplemented by other means, such as conversion of sea water, to meet ultimate needs. Guam and American Samoa have large water supplies locally but rather small supplies in much of their extent, plus the ever-present possibility of salt-water encroachment. Water problems facing the Nation can be divided into six categories: supply and demand, distribution, natural water quality, manmade pollution, variability, and floods. The first five all have the effect of making water of usable quality difficult or expensive to get at certain times or places. The last involves expenditure of large sums to achieve adequate control and reduce damage. as well as to save valuable floodwater now going to waste. The problems at present are largely economic, in the sense that water (or flood control) can be had for a price, but not necessarily at a price that the local economy can bear. Owing to the growth and increasing complexity of the Nation's economy and to the changing distribution of population and water demand, the problems will be difficult to solve. The principal needs are for (1) better understanding of the principles and interrelations of the hydrologic cycle and of the occurrence, availability, and quality of water, (2) improved methods of identifying problems and choosing among alternate solutions--that is, improved methods of water-resource planning, and (3) coordination of effort (including correction and reconciliation of water laws that are hydrologically defective or are contradictory in principle and effect in adjoining jurisdictions in the same hydrologic basin) at all levels of government so as to achieve consistent treatment of problems yet retain control at the lowest possible level, which generally is also the level at which the effort is principally financed. Owing to the growing difficulty and cost of meeting increasing water demands from an essentially fixed supply, the demands may not increase quite as rapidly as projected by the Senate Select Committee on National Water Resources. They will, however, strain the limits of available supply in ever larger areas, beginning with the drier areas in the West that are already in trouble. In the Nation as a whole, the needs will be met by increasing surface storage, taking advantage of the enormous capacity of ground-water reservoirs for cyclic storage of surplus surface water, and developing improved methods of waste treatment to enable repeated reuse of water. In this way a total withdrawal demand predicted to rise to 888 billion gallons per day (bgd) by the year 2000 can be met from a total runoff (including ground-water runoff) which in 1895-1955 varied from as little as 50 percent to as much as 140 percent of the average of about 1,200 bgd. New or improved techniques that will be tested as methods of increasing water supplies include (1) reduction of evaporation from reservoirs, (2) reduction of transpiration from areas of low-value phreatophytes, (3) vegetation management to increase watershed yield, (4) improved irrigation practices to reduce avoidable losses of water, (5) improved methods of treatment to reduce water requirements for waste dilution, (6) salvage of waste water for uses for which its quality is suitable, (7) economies in industrial use such as increased reuse in place of 'once through' use, (8) conversion of saline water, (9) weather modification, (10) improved meteorologic forecasting to enable reduction of flood damage and more efficient planning of water use, (11) use of radioactive substances in hydrologic investigations and--ultimately, perhaps-significant reduction in energy costs through improvement of nuclear-energy processes, and (12) improved use and control of ground water. Ground water has been viewed optimistically by some as holding the answer to the Nation's water-supply problems. Actually, though ground-water reservoirs have an enormous and essential contribution to make in furnishing additional water supply and storage capacity, difficulties in locating, evaluating, developing, and managing ground-water supplies will make full utilization of the ground-water reservoirs very difficult. Great progress has been made in recent decades in ground-water hydrology, as well as in other aspects of hydrology, but available information is still highly inadequate as to understanding of both hydrologic principles and areal occurrence of water. A major effort in ground-water research will have to be undertaken if the ground-water reservoirs are to come anywhere near fulfilling their potential as elements of comprehensive multipurpose water management.