BOARD00101 - Laserfiche WebLink

Home Browse Search

. Lake Powell Operations in WY 1999 July 23, 1999 Page 2 00 stream flows, the most critical period of record, the probabilities of water supply, and estimated future depletions. Water not required to be so stored may be released from Lake Powell: . . to the extent it can be reasonably applied in the States of the Lower Division to the uses specified in Article III( e) of the 1922 Colorado River Compact, but these releases will not be made when the active storage in Lake Powell is less than the active storage in Lake Mead, . to maintain, as nearly as practicable, active storage in Lake Mead equal to the active storage in Lake Powell (at the end of the water year which is September 30th ), and . to avoid anticipated spills from Lake Powell (powell considered full at elevation 3695 rather than 3700). Storage equalization and/or spill avoidance criterion in accordance with Article 1I(3) of the Operating Criteria have been the controlling factor when determining releases from Glen Canyon Dam the last several years and will continue to be so unless very dry conditions occur and the minimum objective release criterion (8.23 MAP) in Article 1I(2) becomes controlling. Lake Powell releases are further restricted by the Record of Decision and preferred alternative identified in the Glen Canyon Dam EIS. Those restrictions are as follows: Maximum Flow 25,000 cfs (Can be)ncreased if release to lower basin exceeds 823maf) Minimum Flow 5,000 cfs Ascending Ramp Rate 4,000 cfs\hour Descending Ramp Rate 1,500 cfs\hour Daily Fluctuations When monthly release volume is .600 MAF or less, maximum fluctuation is 5,000 efs, When monthly release volume is .600 to .800 MAF, maximum fluctuation is 6,000 cfs. When monthly release volume is .800 MAF or greater, maximum fluctuation is 8,000 cfs. . These release criteria can only be exceeded when the Beach Habitat Building Flow Criteria (BHBF Criteria) are satisified. There are two parts to the BHBF criteria, a hydrologic trigger and a set of resource triggers. I will not elaborate on the resource criteria decision tree which can get complex. The bottom line for the'resource criteria at present is that critical habitat for Kanab Amber Snail controls and limits any spike flow release to 44,000 cfs at present. The hydrologic criteria are intended to be in agreement with and comply with both the 1968 and 1992 Acts, and are as follows: I. If the January forecast for the January - July unregulated spring runoff into Lake Powell exceeds 13 million acre-feet (about 140% of normal), or 2. Anytime a Lake Powell Inflow forecast would require a monthly powerplant release greater than 1.5 million acre-feet. "' , Satisfying either hydrologic trigger will allow for a BHBF upto 45,000 cfs to occur. & "