7423 - Laserfiche WebLink

Home Browse Search

I 1 I , I I I I I I I I - I I I I I I described above, is not allowed to interfere with primary functions of water storage and delivery. other incidental objectives do not significantly the operation of the dam, but are addressed when will not interfere with the primary functions. Flood control: Existing space at Lake Powell can be used as credit toward the space which must be reserved at Lake Mead for flood control. the The drive they River regulation and water quality: Glen Canyon Dam has not been used significantly for river regulation or water quality control. Recreation: Summertime releases are kept above 3,000 cfs for white-water rafting. Fish, wildlife, and other environmental factors: winter releases are kept above 1,000 cfs. (During the Lake Powell filling period, special releases were made for a time to enhance the habitat for bass in Lake Mead. Eventually, those releases were ruled to be interfering with water conservation principles and were ended.) Flood Releases Are A Function Of Reservoir Level Targets, Uncertainty In Runoff, And operating Rules For Handling Increases In Forecast Runoff Under current operations, the annual risk of making flood releases is estimated to be about one in four (Appendix 0, Section III). Several factors influence the frequency of flood releases. The dam is operated to address two goals: (1) maximize water storage for later delivery, and (2) minimize the magnitude and frequency of flood releases. These goals conflict with each other, because it is not possible to increase storage without increasing the risk of flood releases. This is because reservoir inflows cannot be perfectly predicted. The closer reservoir levels are brought toward full capacity during the year, the more likely it is that unanticipated inflows will require flood releases. Conversely, avoiding flood releases by lowering the filling target for the reservoir increases the likelihood that unexpected shortfalls in runoff, or 35