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Navajo Reservoir is a rolled earth-fill embankment constructed across the mainstem of the San <br />Juan River about 34 miles east of Farmington, New Mexico. The reservoir has a total capacity <br />of 1,708,600 acre-feet of which the active capacity is about 1,036,100 acre-feet. The remainder <br />of the storage consists of 659,900 acre-feet of inactive capacity and a dead storage pool of <br />12,600 acre-feet. At its normal high water line, the surface area of the reservoir is about 15,610 <br />acres. <br />The reservoir holds a junior New Mexico storage permit with a 1955 priority. This represents a <br />junior water right relative to the major existing irrigation and industrial water rights on the San <br />Juan River in New Mexico and the reservoir is also junior to most of the major water rights <br />decreed for diversion from the San Juan, Navajo, Piedra and Pine rivers in Colorado. For <br />purposes of the CRDSS, the reservoir should be assigned an arbitrary priority that is junior to <br />all existing water rights in Colorado (i.e. a 1995 water right) since the reservoir cannot call out <br />upstream junior water rights. <br />Flood control, recreation and fishery flows are secondary operating purposes for Navajo <br />Reservoir that are accomplished by using monthly water supply forecasts provided by the <br />National Weather Service. Under normal conditions, the reservoir is operated in an attempt to <br />fill by the end of the snowmelt season. Using the monthly forecasts, a release schedule is <br />developed which will fill the reservoir, meet downstream demands and reserve the flood <br />surcharge pool above the spillway crest for accommodation of summer rain floods. The <br />forecasts are updated monthly (or more frequently as necessary) and the release schedule is <br />modified accordingly. Normal releases are made through the outlet works although at critical <br />high flows, releases can also be made through the auxiliary outlet works and the headworks of <br />the NIIl' diversion in an effort to fill the reservoir without encroaching significantly into the <br />flood surcharge pool during the snowmelt season. The forecasted inflow is adjusted for known <br />upstream depletions, in particular the transbasin exports by the San Juan Chama Project and <br />filling operations of Vallecito Reservoir. <br />The USBR has developed a flood control/drawdown diagram to regulate the releases. <br />Fundamental to this tool are the following assumptions: (1) The surcharge pool above elevation <br />6,085 (total reservoir capacity = 1,708,600 acre-feet) is reserved exclusively for rain floods; (2) <br />During critical high runoff flows, releases can be made through the outlet works, the auxiliary <br />outlet and the headworks for the NIIl' diversion; and (3) The reservoir will not be drawn down <br />below elevation 5,990 feet (capacity = 659,900 acre-feet). Use of this flood control/drawdown <br />diagram results in downstream releases well below the existing capacity of the downstream <br />channel. <br />Fish and Wildlife Releases. Historically, releases from Navajo Reservoir were made at levels <br />to satisfy the demands of the Navajo Indian Irrigation Project (see following discussion) and <br />the other maj or irrigation and industrial water rights downstream on the mainstem of the San <br />Juan River. Early operational experience indicated that a release of approximately 500 cfs <br />during the irrigation season, together with the inflows from the Animas River, was sufficient to <br />satisfy all of the downstream demands, without shortage. Occasionally, it was necessary to <br />release 600 - 700 cfs at times when the Animas River was unusually low. During the late <br />San Juan & Dolores River Basin Information 2-22 <br />