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<br />, <br /> <br />present time is approximately 2,015,000 acre-feet. Also, transmountain water has been <br />delivered to the reservoir since 1975 in an effort to maintain a permanent pool in the reservoir. <br /> <br />Mulligan Gulch, San Juan Canyon, Nagl Canyon, San Jose Arroyo, Alamosa Creek, and <br />Cuchillo Negro Creek are the major tributaries that discharge into the Rio Grande in this reach. <br />All these streams discharge directly into Elephant Butte Reservoir from the west. As indicated <br />previously, these streams are dry most of the time, but frequently produce flash floods. <br /> <br />A stream gaging station has been operated by the USBR below Elephant Butte Dam <br />since March 1915, Specifically, this stream gaging station is located 1.0 mile downstream from <br />the dam at an elevation of about 4,240 feet. At this location, the Rio Grande drains an area of <br />about 28,900 square miles. Table 2-3 summarizes the monthly and annual flow at this location <br />from April 1915 through December 1995. On an annual basis, the flows averaged 727,898 <br />acre-feet and ranged from 183,394 acre-feet in 1964 to 1,818,789 acre-feet in 1942. Obviously, <br />this gage registers the releases from Elephant Butte Reservoir. Since the reservoir is the main <br />storage facility for the Project, the amount of the release in any particular year is a function of <br />both the demand for project water and available water supply, but the timing of the release has <br />been affected since 1938 by the ability to re-regulate water in Caballo Reservoir. The amount <br />and timing of these releases are discussed in Section 4 of this report. <br /> <br />Caballo Reservoir Area <br /> <br />This reach of the river begins at the above-described stream gaging station and extends <br />downstream 25 miles to the stream gaging station below Caballo Dam. It involves essentially all <br />of what is or was known as the Palomas Valley, and nearly its entire length is inundated when <br />Caballo Reservoir is full. Elevations range from about 4,240 feet at the gaging station below <br />Elephant Butte Dam to about 4,150 feet at the gaging station below Caballo Dam. As shown on <br />Plate 1, the City of Truth or Consequences is located along the Rio Grande in the upstream part <br />of the reach. <br /> <br />Caballo Reservoir was constructed as a flood control unit of the Rio Grande Project <br />during 1936-38 with storage operation beginning in February 1938. In addition to flood control, <br /> <br />2-6 <br /> <br />r .~. Cr,.. <br />.... '.... ;,J" <br />