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<br />LJ;,345 <br /> <br />with the variation in water availability upon junior appropriators, Thus, <br />although a large quantity of unconsumed water does exist in this region, <br />in many instances new appropriations from this source may not be a reliable <br />means of obtaining water for new uses. <br /> <br />", <br /> <br />Unappropriated Ground Water <br /> <br />Shallow ground water resources are very large in the Upper Mis- <br />souri River Basin, but they are distributed most unevenly (Missouri Basin <br />Inter-Agency Committee, 1971).14 The immense shallow ground water reserves <br />in Nebraska, for example, are located far from the sites of anticipated <br />large increases in water demand. By contrast, the upstream areas in ,Mon- <br />tana and Wyoming, where major energy developments are occurring, possess <br />reserves only slightly greater than mean annual surface run-off. Shallow <br />ground water resources are limited in prospective energy development areas <br />and in the area of urban growth near Denver. Much irrigation in the region <br />draws upon shallow ground water and may be expected to do so increasingly <br />in the future. <br />Water law in the Western states is coming to recognize increas- <br />ingly the inseparable nature of surface water and ground water. The base <br />flow of perennial streams generally is supported by inflow of ground water, <br />and, conversely, ground water reserves are often fed by surface water in- <br />filtration. Thus most shallow ground water depletions reduce surface flows <br />and withdrawals from surface, waters affect ground water availability. <br />Ground water which is classified as tributary to surface waters is gener- <br />ally managed on a coordinated basis with the associated surface water. <br />Only ground water which is not tributary may be mined without regard to its <br />effect upon surface water availability. <br />Deep ground water resources (deeper than 1,000 feet below the <br />surface) are thought to be even more extensive than reserves in shallow <br />aquifers, although quantitative estimates are not available (Missouri Basin <br />Inter-Agency Commission, 1971),15 The problems associated with the use of <br /> <br />. . . - ~"Y <br /> <br /><:::,:;::,:;?</S,:f;'>:;:.:;:,~~ <br /> <br />..... .::....:': :.'..;...... <br /> <br />.-' ....~ <br />..'., <br />.'.-." .... ........... <br />. .-. .:.....:......:.:.-..(::,.';: <br />. ," :'..;..::"." ,.' ~..' . ""::.;; ::..- <br /> <br />.... <br /> <br />22 <br />