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001083 section 7.1. The levels of discharge specified in the flood control regulations and used by CRSM are the following: Level 1 = 19,000 ft3js Parker Powerplant capacity Level 2 = 28,000 ft3js Nondamaging release limit Level 3 = 35,000 ft3js Approx. Hoover Powerplant capacity Level 4 = 40,000 ft3js Historic floodway Level 5 = 73,000 ft3js Hoover controlled discharge capacity The minimum average release computed in step 1 is next compared to the assumed discharge level. If the computed release is greater than the assumed discharge level used in the computation, then the proce- dure is repeated by recomputing the minimum average release using the next higher discharge level in the computation. When the iteration procedure is complete, i.e., the computed release is less than or equal to the discharge level used in the computation, then one final check is made. If the computed release is less than the discharge at the next smaller level than the level used in the final computation, then the minimum average release is set equal to the discharge at the next smaller level than the level used in the final computation. The release computed by this flood control procedure is the minimum average release for the month. If any other criteria call for a larger release during a given month, like downstream demands, then the larger amount will be released. The CRSM, however. will never decrease the releases from Mead less than the minimum average release computed by the procedure. This procedure is in effect in months January through July, the forecast season. Drawdown Season The second flood control procedure is used in the drawdown season, August through December. The flood control regulations specify monthly minimum vacant space requirements for Lake Mead that are intended to provide a gradual drawdown of the reservoir system. These values, which are used by the CRSM, are as follows: August 1 September 1 - October 1 November 1 December 1 January 1 1.50 mi 11 i on 2.27 million 3.04 million 3.81 million - 4.58 million 5.35 mi 11 ion acre-feet acre-feet acre-feet acre-feet acre-feet acre-feet The regulations specify maximum amounts of space in Lake Powell, Flaming Gorge, Blue Mesa, and Navajo Reservoirs that can be credited towards the Lake Mead space requirement. These values are respect- ively 3,850,000; 1,507,200; 748,500; and 1,036,100 acre-feet. In the CRSM, the operation of the Upper Basin Reservoirs is determined before the operation of Lake Mead. In this way, the model knows what the vacant space in these reservoirs will be at the end of the month and can use these values to determine Lake Mead flood control opera- tions. 39