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00lO!)O The required space in Lake Mead is obtained in the model each month by setting the target storage contents for the month to the level that will provide the required space. The release for flood control space-building is then determined so that the reservoir will reach the target storage level. The model, however~ constrains the release during the space-building season to 28,000 ft~/s as specified in the flood control regulations. As in the January to July period, the release may be increased over that which is required for space- building by other criteria such as downstream demands. Exclusive Space Requirements The third flood control procedure is used all year. The flood control regulations specify a minimum space of 1.5 million acre-feet in Lake Mead at any time for control of rain floods. Since the CRSM is a monthly model, the model can only deal with this requirement on a monthly basis. Target content levels are set to maintain the required minimum space. The model will force releases to maintain this minimum space on a monthly basis. Distribution of Excess Releases Releases from Lake Mead due to flood control that are in excess of normal downstream demands or scheduled surplus deliveries are distributed by the CRSM each month as follows. Excess releases are divided equally between CAP and MWD. If either aqueduct reaches its maximum capacity and there is excess release remaining, the other aqueduct can take the remaining excess, up to its maximum capacity. After both aqueducts reach thei r maximum capacities, any remai ning excess flows to Mexico. In the years before CAP can take a surplus (specified in the input file), MWD can take all excess releases up to its maximum capacity. 8.4 Surplus Strategy The surplus strategy is the decisionmaking process used to (1) antici- pate spring runoff in exces~ or surplus of normal demands and storage space, and to (2) distribute this surplus water to users throughout the water year to prevent flood control releases. The CRSM has a number of surplus strategies that vary in the degree of assurance the strategy gives in being able to anticipate and distribute surplus water without having to make flood control releases. The amount of assurance, referred to as the assurance level, is input to the model as a probabi- lity and serves as the identification of the strategy chosen. For example, an assurance level of 0.95 schedules appropriate surplus releases from Lakes Powell and Mead and distributes them throughout the water year to assure that unscheduled releases for flood control will be expected in approximately 5 percent of the years of operation. The surplus strategies in the CRSM are optional. The strategies can be turned off by simply setting the assurance level to zero. If this is done, the CRSM does not schedule any surplus releases from Lakes Powell 40