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Hydrolouv Gunnison River The Gunnison River watershed includes the West Elk Mountains, northern San Juan Mountains, the southern portion of Grand Mesa and the eastern side of the Uncompahgre Plateau. Three major rivers contribute to the Gunnison's flow at the study area; the North Fork of the Gunnison, the south Fork of the Gunnison, and the Uncompahgre River. The South Fork and Uncompahgre River drain high plateaus and mountains and much of their watersheds lie above 8,000 to 10,000 feet elevation. The North Fork of the Gunnison drains an area of mostly lower elevation land and may have an earlier .melt-out. Discharge data for the Gunnison River is obtained from the Whitewater gauge located downstream from our study site. This gauge has been operated since 1897, with the exception of years 1928 to 1944. The history of dam construction on the Gunnison River system is summarized here to help understand if any flow changes have occurred as a result of these projects. Taylor Reservoir on the Taylor River, a large tributary of the South Fork of the Gunnison was constructed in 1937. Three reservoirs were constructed on the South Fork; Blue Mesa Dam was completed in December 1965, Morrow Point Dam was completed in January 1969, and Crystal Dam was completed in December 1975. Thus; four large dams and reservoirs occur on the South Fork of the Gunnison, while no large dams occur on the North Fork. The Uncompahgre River remained undammed until 1986 when the Ridgeway Reservoir was constructed. Total annual flow by water year is shown in Figure 2. High water years on the Gunnison have total annual flows of greater than 2,500,000 acre feet, while low flow years have flows of less than 1,000,000 acre feet. The flow record is broken into two segments for analysis; 1897 to 196.5 (pre-dam), and 1966 to 1993 (post dams). Table 1 shows mean (and standard deviation) of total annual flow for these two periods and indicates that mean flows were very siunilar in the two periods, averaging approximately 1,800,000 acre feet. Thus, dam construction has not diminished the total annual flow. 5