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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />As the irrigation season progresses, estimated index flows become known index flows <br /> <br /> <br />and the Compact obligations are re-evaluated. The water administrators periodically <br /> <br /> <br />(approximately every 10 days) compare the re-evaluated Compact obligations to actual <br /> <br /> <br />deliveries and adjust the curtailment percentage if required. <br /> <br />IV.5 PREVIOUS STUDY TREATMENT OF COMPACT <br /> <br />Two previous studies of water availability to a new reservoir project in the San <br /> <br /> <br />Luis Valley provide examples of consideration of the Rio Grande Compact. The <br /> <br /> <br />following general descriptions are provided to illustrate the nature of the Compact <br /> <br /> <br />consideration in these studies. <br /> <br />Tipton Study <br /> <br />The Tipton Study (Tipton, 1939) investigated the effect of the proposed San Luis <br /> <br /> <br />Valley Project (I.e. Wagon Wheel Gap Reservoir) on the stateline outflow under <br /> <br /> <br />various assumed conditions and the resulting effect on the operation of Elephant <br /> <br /> <br />Butte Reservoir. The investigation was based on the relatively high runoff <br /> <br /> <br />hydrologic conditions of 1890 through 1938. Average annual flows at Del Norte <br /> <br /> <br />during 1890-1938 averaged greater than 700,000 af compared to the 1948 -1985 annual <br /> <br /> <br />average of less than 600,000 af. Given this high runoff study period, Tipton <br /> <br /> <br />concluded that under any of the assumed conditions a reservoir at Wagon Wheel Gap <br /> <br /> <br />could have operated most of the time without restriction for the Compact. In his <br /> <br /> <br />scenario with the Closed Basin Project operating, Tipton concluded that a Wagon <br /> <br /> <br />Wheel Gap Reservoir could have operated freely for the entire study period and <br /> <br /> <br />substantial credits would have accrued to Colorado during those periods when <br /> <br /> <br />Elephant Butte was not spilling. <br /> <br />The Tipton Study indicated that operation of a 1,000,000 af Wagon Wheel Gap <br /> <br /> <br />reservoir would reduce water shortages from Del Norte to Alamosa from an average <br /> <br />annual (1890-1938) value of approximately 180,000 af to less than 20,000 af. <br /> <br /> <br />Operation of a 1,000,000 af Wagon Wheel Gap would create an average annual (1890- <br /> <br /> <br />1938) supply of approximately 650,000 af to mainstem water users. <br /> <br />33 <br />