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<br />~'j:(i.::;:;:\;~f;~r~:,:~;f')':.\:;,~:::':'>:::f'~~~~'f.;:,::..., :~::;. :::~>::'.'~j";:_', <br /> <br />-.' - r ':::"5b:;:,:~~::'\.:;~..~>.;~};.:'~::::"~; :;.v::;:,~;1;t~':.;~,:._.,t.t.:.i,:\~~'~; <br />. . ,":. ';', . ".- ;-~.""~ '. .:-. ." . .-.. . <br />,.....'., <br />ii:/~:.: <br /> <br />.'../..,. <br />~:. . <br /> <br />~;::~2.:, <br />:i::~~~ <br />..,"':......., <br />....... <br />';'.,,: <br /> <br />o <br />(}l <br />~ <br />ex, <br /> <br />In the 1940's the average ground-water pumpage was <br /> <br /> <br />1,200 acre-feet per year, in the 1950's, 11,000 acre-feet <br /> <br /> <br />pe~ year, and in the first half of the 1960's, 25,000 acre- <br /> <br /> <br />feet per year. The year of greatest pumpage was this year, <br /> <br /> <br />when 29,700 acre-feet was withdrawn. On the other hand, <br /> <br /> <br />the return flow to the Arkansas River was reduced by <br /> <br /> <br />(:.. :-.." <br /> <br />'"'- .,.,. <br />-....... <br /> <br />....1'.. <br />,.;;,!,,~:: <br />::,~,:.::.,~...: <br /> <br />..~ '., <br />--:;~,:::': <br /> <br />....: <br /> <br />20,000 acre-feet from 1940 to 1963. The similarity of <br /> <br />'.~:.:'::::':~ <br />.~<.::\; <br />.'.- ,.'~. <br />"..;".":::, <br />t~~~ <br />.~'!.t <br />. t;~i~ <br /> <br />,.;<...; " <br />;iA/{: <br />-..,.';::-;.'. <br /> <br />the trends is apparent. A significant cause of the reductions <br /> <br /> <br />of return flow is the increased pumpage of water from wells. <br /> <br /> <br />Phreatophyte growth has increased over this same period <br /> <br /> <br />and has caused a part of the reduction in return flow. <br /> <br />::, ..'~. <br /> <br />The irrigation-well development in the Arkansas Valley has <br /> <br />)}\~ <br />"":."J:" <br /> <br />been beneficial in that the wells provide water to crops <br /> <br />;,:"(\;;: <br />~(~;:i~ <br /> <br />during times of def~cient surface-watersupply. <br /> <br />I. ':"~ ',: ;, ~',: <br /> <br />>{j~~ <br /> <br />;~.::~:r!;i <br />. :-::. .:;>,:,'~ <br />.;:;~(~>; <br />~~:;~j <br />i <br /> <br />..>J/{ <br /> <br />However, <br /> <br />these wells were drilled and were used with little evaluation <br /> <br />of their effect on the surface-water supply. <br />To minimize adverse effects and to achieve maximum <br /> <br />use of the available water supply, ground water and surface <br /> <br />water must be developed and managed as a single supply, but <br /> <br /> <br />development and management cannot be planned properly until <br /> <br /> <br />the operation of the hydrologic system is quantitatively <br /> <br />described. <br /> <br />.;......:.:., <br /> <br />The U.S. Geological Survey in cooperation with the <br /> <br />:-.,,~ (,:;,:. <br />.'~'.~ <br /> <br />Colorado Water Conservation Board and the Southeastern <br /> <br />.-........ <br />. ,"'." <br /> <br />, "'\. <br /> <br />Colorado Conservancy District is studying the Arkansas <br /> <br /> <br />Valley in order to evaluate the hydrologic system so that <br /> <br /> <br />the effects of selected changes in water management can be <br /> <br /> <br />::? <br />