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<br />Orl316:) <br /> <br />fI' <br /> <br />CHAPTER III <br /> <br />WATER SUPPLY <br /> <br />Water Resources <br /> <br />The source of irrigation water for the South San Juan and Shiprock <br />projects is the San JUan River at the Navajo Dam 'site, located about 3.5 <br />miles below the mouth of Pine River. The flow at the Blanco gage is <br />considered to be representative of the flow at the dam site since any <br />inflow from the tributary drainage area between these two points is <br />practically negligible and consists almost entirely of flash run-off <br />from local storms. <br /> <br />.. <br /> <br />. The average annual recorded run-off of the San Juan River near <br />Blanco for the years 1930 to 1951 was 1,010,800 acre-feet. This <br />recorded run-off was adjust ed to allow for new upstream developments <br />during this period and for all potential within-basin upstream develop- <br />ments and the potential Weminuche Pass diversions to San Luis Valley. <br />These aQjusted flows, tabulated by months in Table VII on the following <br />page, represent the water available for regulation at the Navajo Reservoir <br />site for the South San Juan and 'Shiprock projects and for other potential <br />and existing downstream developments. The adjusted flows average 885,900 <br />acre-feet annually. Requirements for other potential and existing down- <br />stream developments are estimated to average 23,000 acre-feet annually <br />after allowing for irrigation diversions by-passing the Blanco gage and <br />for estimated usable return flows below the gage. Thus an average of <br />862,900 acre-feet annually would be available for regulation at the <br />Navajo site for the South San Juan and Shiprock projects, assuming no <br />transmountain diversion to the potential San Juan-Chama project. <br /> <br />Potential upstream developments considered in determining modified <br />flows of San Juan River at Blanco consist of the Dulce, O'Neal Park, and <br />Pine River extension projects; irrigation of miscellaneous lands above <br />Rosa, N. Mex.; and transmountain diversions to San Luis Valley from <br />Pine River and Weminuche Creek. Table VIII on page 24 lists the acreages <br />of the various projects and areas located upstream from the Navajo Dam <br />site. Should any of the potential developments fail to be realized, the <br />modified flows at Blanco would be increased accordingly. <br /> <br />. <br /> <br />22 <br /> <br />. <br />'L <br /> <br />