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<br />."J '.' '-, l 'I
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<br />
<br />and minor streams, although ongoing plans and programs are
<br />striving to alleviate many of the problems.
<br />
<br />Ground Water Availability
<br />
<br />Ground water is the principal source of supply for a
<br />number of purposes in many areas of the Missouri River Basin.
<br />Fortunately, the Basin has been endowed with abundant
<br />ground water of quality suitable for most purposes. Shallow al-
<br />luvial deposits are found along most major watercourses. Also,
<br />extensive quantities of relatively shallow ground water underlie
<br />large portions of Nebraska, western Kansas, eastern Wyoming
<br />and Colorado, and parts of Missouri and South Dakota. In all,
<br />reserves lying at less than 1,000 feet deep are estimated at
<br />greater than 3 billion acre-feet 3 Further, large amounts of
<br />ground water are known to exist in the Basin's extensive deep
<br />sandstones and limestones at depths greater than 1,000 feet.
<br />Although these deeper deposits contain more water than the
<br />more accessible shallow aquifers, its use is limited by exces-
<br />sive pumping costs and variable quality.
<br />
<br />Water tables in some areas of the Basin are declining
<br />due to withdrawals in excess of recharge. Areas experiencing
<br />significant adverse effects include, among others, northwestern
<br />Kansas, eastern Colorado and Wyoming, northwestern Ne-
<br />braska, portions of the Platte and alue Basins in Nebraska, and
<br />parts of eastern Missouri. On the other )land, the ground water
<br />level is rising in south-central Nebrasila due to irrigation canal
<br />seepage and infiltration from irrigated lands.
<br />
<br />Recently, efforts have been concentrated .on gaining a
<br />better understanding of the complex nature of the Basin's
<br />ground water resource so that it can be more efficiently utilized
<br />for domestic, agricultural and industrial purposes.
<br />
<br />Ground Water Quality
<br />
<br />The quality of ground water in the Basin is variable.
<br />Water of highest quality is derived from dune sand, such as
<br />found in north-central Nebraska, and from C!eep igneous and
<br />metamorphic rock formations. Major sources of ground water
<br />are generally sedimentary deposits and valley alluviums. In the
<br />former, the abundant shallow sandstone and limestone de-
<br />posits generally yield water of adequate quality for most uses.
<br />Water recovered from valley alluviums is influenced by the
<br />quality of the surface water, the rock types in the valley, and
<br />the surrounding vegetation. Alluviums along many streams
<br />contain water with high sulfate concentrations.
<br />
<br />Ground water containing concentrations of total dissol-
<br />ved solids exceeding 2,000 miligrams/liter, considered very
<br />poor quality, are found in highly developed aquifers in eastern
<br />Montana, central South Dakota, eastern Iowa and northwestern
<br />Missouri.
<br />
<br />3:Missouri Basin Inter-Agency Committee, op. cit., Vol. 1, p. 63.
<br />
<br />Interrelationship of Surface
<br />and Ground Water
<br />
<br />With increasing development of both surface and ground
<br />water resources, their hydrologic interrelationship is becoming
<br />increasingly more important to users. Several types of effects
<br />have resulted from manmade water and land resource de-
<br />velopments. One of the most significant effects occurring in
<br />certain areas of the Missouri Basin has been the reduction of
<br />inflow to the surface system caused by withdrawals of related
<br />ground water. Ground water pumping for sprinkler irrigation is
<br />diminishing streamflows otherwise available for instream and
<br />offstream uses in parts of Colorado,. Kansas and Nebraska.
<br />Other notable effects of development occurring wnhin the Basin
<br />include alteration of runoff and infiltration caused by land use
<br />changes and increased aquifer recharge due to surface water
<br />storage.
<br />
<br />EXISTING MAJOR WATER
<br />RESOURCES DEVELOPMENT
<br />
<br />Water resources development in the Missouri Basin
<br />coincided with its settlement, which began to accelerate slightly
<br />more than 100 years ago. The initial developments were ear-
<br />then structures built on smaller streams to meet single-purpose
<br />needs, primarily water supply. Since the 1930's, surface water
<br />developments have often been supplemented with ground
<br />water developments, particularly for privately developed irriga-
<br />tion on the plains of Colorado, Kansas and Nebraska.
<br />
<br />In the past 30 years, a number of major reservoirs have
<br />been constructed in the Basin. Most of these projects were built
<br />to serve multiple purposes and differed markedly from the ear-
<br />lier single-purpose developments. Under the multipurpose
<br />scheme, numerous surface water projects have been built,
<br />each one serving a number of important purposes---such as
<br />irrigation water supply, flood control, hydroelectric power gen-
<br />eration, navigation, recreation and fish and wildlife enhance-
<br />ment, and cur<ently, industrial water supply. Some of these
<br />projects are shown on Figure 6.
<br />
<br />Perhaps the most prominent multipurpose projects in the
<br />Basin are the six major Missouri River main stem
<br />reservoirs--Fort Peck, Sakakawea, Oahe, Sharpe, Francis
<br />Case, and Lewis and Clark. These large developments were
<br />constructed by the Corps of Engineers under the Pick-Sloan
<br />Missouri Basin Program, originally adopted by the Congress in
<br />1944. Each of these projects provides benefits for most or all of
<br />the purposes listed. In addition, other large multipurpose proj-
<br />ects have been or are being built by the Corps of Engineers
<br />and the Bureau of Reclamation in every subbasin in the Mis-
<br />souri Basin. Among these are Canyon Ferry in the Upper Mis-
<br />souri Subbasin; Boysen and Yellowtail in the Yellowstone;
<br />Shadehill and Keyhole in the Western Dakotas; Jamestown in
<br />the Eastern Dakotas; Seminoe and Glendo in the Platte-
<br />
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