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<br />o <br />(-' <br />..... <br />W <br />c..'=l <br />-...! <br /> <br />d. San Simon Basin Study <br /> <br />In the watershed of San Simon Creek, a tributary of the Gila <br />River in Arizona, a study is proposed for evaluation of the effects <br />of detention reservoirs on the flow downstream. Two such reservoirs <br />of 3,500 and 2,400 acre-feet capacity have been constructed on publiC <br />lands administered by the Bureau of Land Management and others are <br />proposed; of which one would have 27,000 acre-feet detention capacity. <br />Downstream is Coolidge Dam which impounds waters of the Gila for the <br />San Carlos Irrigation District and the District officials have pro- <br />tested the construction of detention reservoirs by the Bureau of Land <br />Management, claiming that inflow to its reservoir is depleted thereby. <br />The study program is still in the negotiation stage. <br /> <br />e. Other Studies <br /> <br />Mr. H. G. llobet, State Conservationist of Nebre.slla, reported <br />that they have some sub-watersheds in the Upper Salt (pilot) projects <br />instrumented which, in a few years, should give some information re- <br />garding the effectiveness of land treatment and detention reservoirs. <br />He also said that the Agricultural Research Service Hydrologic Inves- <br />tigation Station at Hastings, Nebr., has some infonation on two <br />watersheds - one treated and one untreated - but that neither of the <br />watersheds had detention reservoirs. <br /> <br />An inquiry directed to Mr. L. L. Kelly, who is at the Agricultural <br />Research Service office at Hastings, Nebr., brought the following reply: <br /> <br />"The Agricultural Research Service is interested in the <br />effects that upstream programs may have on downstream water <br />yield and is doing some work on it. <br /> <br />"First, we are about to get under way in analysing all <br />available data to determine the dependable flows from suall <br />watersheds. This study will be pointed toward the need of <br />agricultural agencies for design data for suall water supply <br />structures from the size of a stock water pond to that of a <br />small municipal structure or irrigation facility of perhaps <br />well under a hundred square miles drainage area. In this <br />study we will investigate possible differences in runoff trom <br />treated and untreated areas. We hope that the investigation <br />will result in a set of frequency curves for each significant <br />physiographic area, and which will reflect differences in size <br />and condition of the watersheds. This is probably not the type <br />of study you had in mind, but I thought it might be of some <br />interest. <br /> <br />"Second, we are studying and considering the methods and <br />procedures by which existing data might be used in Daking an <br /> <br />C/l-ll <br />