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<br />Some of the proposed stations are intended to determine channel <br />losses or consumptive uses in reaches of a stream where the difference in <br />flow between upstream and downstream stations is only a few percent. <br />Records for such determinations must be of. high accuracy. The cost of <br />stream flow records increases rapidly as the standards of accuracy increase. <br /> <br />Estimated cost of installation of the proposed new stations is <br />about $2,000,000 and annual cost of operation about $1,000,000, which would <br />be large items in our budget. It is increasingly difficult to obtain funds <br />in connection with specific interstate coni;pact needs. Means of financing <br />additional stations requires considerable ,thought. <br /> <br />More information is needed also on ground water. A true under- <br />standing of stream flow requires comprehensive information about the <br />relations between surface and ground water. Studies of channel losses or <br />return flow from irrigated areas require investigation both of surface and <br />ground water. Our only intensive studies of ground water in the Colorado <br />River Basin have been in. the Salt and Gila basins in Arizona, Las Vegas <br />Valley in Nevada, and the Grand Junction ?Xea in Colorado, all places where <br />progressive lowering of water levels has indicated overdeve1.opment of ground <br />water. For the rest of the basin we know very 11 ttle about ground water, <br />its relation to stream flow, possibilities of development by wellS, or the <br />effect of such development upon stream flow. <br /> <br />Additional information is needed about chemical characteristics of <br />the ground and surface water and sediment loads transported by the streams. <br />As a rule, in the Colorado River Basin water of best quality is in headwater <br />areas, and the quality tends todeteriora.te downstream, especially with use, <br />even to the extent of being unfavorable for certain uses. Some tributaries <br />contribute volumes of sediment and dissolved minerals disproportionately large <br />in relation to their volumes of water. Additional information is nee.ded about <br />the geographical origin of dissolved solids and sediments, before ameliorative <br />measures can be planned intelligently, particularly with respect to proper <br />allowances for sediment accumulation in upstream reservoirs. <br /> <br />The Navy Department, the Bureau, of Reclamation and the Geological <br />Survey made a comprehensive survey of Lake Meaa. in 1949, and we hope to have <br />a detailed report ava:l.lable within the next few months. Conclusions as to <br />sediment accumulations indicate that past estimates of the economic life of <br />the .reservoir have been conservative. 'rhe survey shows that the reservoir can <br />hold 35 times as. mu~h sediment as it received in the first 14 years of its <br />history. It can store about 17 times as much as that 14-year accumulation and <br />still have a water-storage capacity of 13 million acre-feet, approximately the <br />average annual inflow, and thus provide some holdover capacity for the Lower <br />Basinls Compact allotment. It is likely:' therefore, that the uset'ul life of <br />Lake Mead will be measured in centuries.' The survey also gives data for <br />predicting the pattern of sedimentation in the proposed Glen Canyon and other <br />reservoirs in the Colorado River BaSin. <br /> <br />Although the Lake Mead survey gives answers to many perplexing <br />questions, it also poaes new ones, and high-lights our need for greater <br />knowledge of the hydrology of the Colora.do River :Basin. It shows that we <br />do not know enough about the fundamental relations of the water, dissolved <br />load and sediment in the reservoirs and,rivers, nor about the areas of origin. <br /> <br />-8- <br />