WSP01924 - Laserfiche WebLink

Home Browse Search

,- ~ . " " ~ . i 13 also indicated that young-of-year Colorado squawfish, from late summer through fall, preferred natural backwater areas of zero velocity and less than 1.5 feet in depth over a silt substrate. Juvenile Colorado squawfish habitat preferences are similar to the young-of-year fish, but juveniles appear to be mobile and adaptable to lotic conditions away from the sheltered environment provided by backwaters. Information on radio-tagged Colorado squawfish that have been observed during fall suggests that fish seek out deepwater areas in the Colorado River (Miller, et al., 1982), as do many other riverine species. River pools and other deepwater areas, especially in upstream reaches, are probably important winter habitats for Colorado squawfish. Very little information is available on the influence of turbidity on the .endangered Colorado River fishes. It is assumed, however, that turbidity is important, particularly as it affects the interaction between introduced fishes and the endemic Colorado River fishes. Since these endemic fishes have evolved under natural conditions of high turbidity, it is concluded that the retention of these highly turbid conditions is an important factor for these endangered fishes. Reduction of turbidity may enable introduced species to gain a competitive edge which could further contribute to the decline of the endangered Colorado River fishes. Areas of Imoact and Concern The reach of currently known occupied habitat that will receive the most impact due to the upstream water withdrawals related to the proposed Ruedi II and Green Mountain water sales is the mainstem Colorado River between Palisade, Colorado (RM 185), and the confluence with the Gunnison River (RM 170) (Figure 1). This reach of the Colorado River is regulated by two large agricultural diversion structures and one dam barrier located in nearby upstream areas. The first of these water diversions is located immediately upstream from RM 185. Known as the Grand Valley Irrigation Company diversion, this structure diverts up to approximately 640 cfs from the Colorado River during the growing season (April to October) and smaller amounts during the winter for stock watering. It is thought that adult squawfish are able to successfully swim over this low-head structure during all but extremely low- flow stages. Until the 1980's, cracks and seepage areas in the diversion dam provided some flow in the Colorado River below the structure, even during extreme low-flow conditions, but recent repair has made it virtually leak- proof (Henderson, 1985). Another instream feature known locally as the Price Stub Dam is located about 3 miles upstream from the Grand Valley Irrigation Company diversion (RM 188.2). Built in the latter 19th century for irrigation purposes, the dam is 8 feet high and spans the entire width of the river. It is likely that this structure acts as an upstream barrier to fish migration during most flow stages.