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03/13/96 15:05 12303 295 6933 FISH & WILDLIFE -)44 R 0 4 Denver @006/011. <br />razorback sucker and pond-reared adult razorback sucker that were stocked in the <br />Gunnison River in 1994 and 1995, no wild riverine razorback sucker have been <br />collected in the Gunnison River since 1981 (Holden at al. 1961). <br />Both the South Fork and the North Fork of the Gunnison River are regulated <br />by Federal dams and reservoirs upstream of warmwater reaches. The largest of <br />these reservoirs is the Aspinall Unit, which is a series of three federal (U. S. <br />Bureau of Reclamation [BR]) reservoirs and dams on the upper South Fork or main <br />Gunnison River. Taylor Park Reservoir is located further upstream on the South <br />Fork. Other water development projects constructed by BR include Paonia Dam on <br />the North Fork, Crawford Dam (Smith Fork Project), on the Smith Fork, Ridgeway <br />Reservoir, (Dallas Creek Project), on the Uncompahgre River, and Fruitgrower's <br />Reservoir. Although these three major reservoirs and other smaller water <br />projects occupy a portion of the Gunnison River that is upstream from historic <br />habitat of the four endangered fish, alterations in flow and water quality have <br />significantly affected the downstream warmwater reaches. <br />Historically, the Gunnison River was typical of Colorado River basin <br />tributaries with high, turbid spring flows and clearer low flows from lace summe- <br />through winter. However, the timing of water delivery has been significantly <br />altered by water development projects. The greatest change caused by the <br />Aspinall Unit is the reduced magnitude of spring runoff. The mean-monthly flows <br />measured at the U. S. Geological Survey (USGS) gauge at Whitewater. Colorado have <br />declined about 25% in May and 32% in June since construction of the Aspinall <br />Units. In contrast, flow during the remainder of the year has increased, <br />particularly during the winter when average monthly flows are more than 1002 <br />greater than pre-Aspinall flows. In general. spring and early summer flows have <br />declined, and fall and winter flows have increased (Figure 1). A secondary <br />effect is that water temperatures have decreased during summer and increased <br />