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<br />pine, Douglas fir, true firs, and Ponderosa pine. Twenty-
<br />three percent of the forest land is in the Ozark Plateaus
<br />where the chief timber types are oak-pine, oak-hickory,
<br />elm, ash, cottonwood, and other hardwoods.
<br />
<br />Water Resources
<br />
<br />Water is one of the basic resources necessary to
<br />sustain life, and its abundance or scarcity influences the
<br />culture, economic structure, and environment for human
<br />habitation. The variability of this influence is especially
<br />evident in the Missouri River Basin from its more
<br />densely populated humid eastern sections to the more
<br />sparsely populated and generally arid western sections.
<br />Both the form and magnitude of water resources
<br />available for use vary considerably within the basin.
<br />Precipitation varies in form and in the amount received
<br />seasonally and annually. Runoff is, in part, predictable
<br />seasonally where the precipitation is received as snowfall
<br />and builds up during the winter, particularly in the
<br />mountainous areas. Conversely, rainfall is largely unpre-
<br />dictable, and may be received in the form of intense
<br />storms or relatively light falls spaced intermittently.
<br />Periods of drought are not uncommon in some parts of
<br />the basin in any year, or a succession of two or more
<br />years, and occasionally throughout the basin, as in the
<br />1930's.
<br />As can be noted from the average annual precipita-
<br />tion values shown earlier in figure 5, much of the basin
<br />receives, on the average, less precipitation than the
<br />vegetative consumptive-use demand or potential evapo-
<br />transpiration. This situation not only dictates the type
<br />of vegetation naturally adapted or that can be grown in
<br />the climatic zones already illustrated, but it also
<br />influences the runoff. in many areas, runoff is experi-
<br />enced only when the precipitation intensity exceeds the
<br />ability of the soil to absorb it.
<br />Since the beginning of settlement in the basin there
<br />has been progressive development and management of
<br />water resources to support the population and economic
<br />activity. Existing storage reservoirs in the basin have a
<br />gross capacity of over 106 million acre-feet serving such
<br />purposes as municipal, industrial, livestock, irrigation,
<br />power, low-flow augmentation, fish and wildlife, recrea-
<br />tion, and flood control. In addition to the storage of
<br />surface waters, diversions of water for beneficial uses are
<br />also made from both streams and from ground water.
<br />Any analysis of water resource availability within the
<br />basin must be associated with an understanding of the
<br />following principles:
<br />
<br />(I) Historic streamflow measurements are not
<br />indicative of current conditions or water avail-
<br />ability without adjustment for subsequent
<br />utilization, storage control, and cultural land
<br />practices.
<br />
<br />16
<br />
<br />(2) Ground-water utilization in the basin affects
<br />streamflow in varying amounts, depending on
<br />the hydrologic relationships of the ground-water
<br />aquifers with the streams.
<br />(3) Water visibly appearing in streams or impound-
<br />ments must be analyzed in conjunction with
<br />dedicated water rights, interstate compacts and
<br />court decrees, and current usage to determine its
<br />availability for new and additional uses.
<br />Prior to 1865, streamflow of the Missouri River was
<br />largely unused, but about this same time the influx of
<br />the early settlers of the basin started irrigation and
<br />mining ventures. By 1890, streamflow depletions in the
<br />basin averaged about 1.3 million acre-feet annually and
<br />by 1910, they averaged 5.6 million acre-feet annually.
<br />Between 1910 and 1949, water uses increased at a much
<br />slower rate with streamflow depletions reaching an
<br />average annual level of 6.9 million acre-feet by 1949.
<br />Since 1949, the major features of the basin plan, known
<br />as the Pick-Sloan Plan, were initiated. This acceleration
<br />since 1949 has added to streamflow depletions by about
<br />4.8 million acre-feet. Figure 9 illustrates the growth of
<br />streamflow depletions in the basin.
<br />
<br />FIGURE 9
<br />GROWTH OF STREAM FLOW DEPLETIONS
<br />IN THE MISSOURI RIVER BASIN
<br />
<br />12
<br />
<br /> /
<br /> /
<br /> /
<br /> /
<br /> .....--- .....---
<br /> --
<br /> ~
<br /> /
<br /> /
<br /> /
<br /> /
<br /> ./
<br />/' /
<br />
<br />II
<br />
<br />I-
<br />~ 10
<br />...
<br />"'
<br />ll: 9
<br />u
<br />"
<br />
<br />Q 8
<br />...J
<br />...J
<br />~ 7
<br />z
<br />o
<br />I- 6
<br />"'
<br />...J
<br />"-
<br />~ 5
<br />
<br />...J
<br />"
<br />~ 4
<br />z
<br />"
<br />"' 3
<br />Cl
<br />"
<br />ll:
<br />'!; 2
<br />"
<br />
<br />o
<br />1860 70 80 90 1900 10 20 30 40 50 60 1970
<br />TIME IN YEARS
<br />
<br />Runoff is the amount of precipitation that appears in
<br />surface streams. However, it is the same as streamflow
<br />only when unaffected by artificial diversions, storage, or
<br />other works of man. Some streamflow records within
<br />the basin are fairly representative of natural runoff and
<br />others, with minor adjustment, are useful for such a
<br />determination. In all, the records of 483 gaging stations
<br />within the basin and 57 peripheral stations were selected
<br />
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