1006 - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I I I I I I I I I I occurs in Table 4 and the resultant cumulative depletions should be used as "ballpark" estimates rather than absolute values. As shown in Table 4, cumul ative depl etions near the Utah-Colorado state 1 ine could range from 2,027 cfs in May, to 83 cfs in August. The addition of the Green Mountain Water Sales increases these values to 2,038 and 113 cfs, respecti vel y. The Cisco USGS gage just across the Colorado border in Utah reflects the flow of most areas used by Colorado squawfish since it is located within the area used by this species. Average monthly flows at the Cisco gage are shown in Table 5 for the period 1962 to 1981. A com- parison of Tables 4 and 5 indicates that the cumulative average deple- tions of the 14 projects plus Green Mountain Water Sales range from a low of about 3 percent of the average flow for August to 17 percent for December, with most months around 10 percent at Cisco. Actual year-to- year variation would be expected to show even greater percentage depl e- tion in below average flow years. This level of depletion would be a significant reduction in flow and would be continuing a trend that has caused the present concern for the species. It is not known exactly how lowered flows affect squawfish reproduction and survival, but this cumu- lative depletion would increase the negative aspects of this phenomenon. Perhaps the least understood section of occupied Colorado squawfish habitat from a flow standpoint is the 15 miles just above the mouth of the Gunnison River. This section of river is below the Cameo gage and is also below major irrigation diversions for the Grand Valley. Flows in this 1S-mile section are not gaged and a rather complex series of withdrawals and return flows exist. During extreme low flow periods, such as 1977-78, this section was nearly dry. The Green Mountain depl etions and augmentations (Tabl es 3 and 4), would directly affect - 38 -