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Description of Existing Model ~ f ' ~ -'~ '" i". -;,',',llI ' U 0 ... .. u '" 3 '. Table 7 lists the overall rankings assigned to the various water rights and water rights groups represented in the model. OPERATIONS OF EXl5TING FACUlTIES The operating procedures of major existing or soon-to-be-developed water supply facilities are represented in the basin model. Specific facilities and systems modeled in detail include the Wayne N. Aspinall Unit (formerly known as the Curecanti Unit), the Uncompahgre Project, the Bostwick Park Pro- ject, the Dallas Creek Project, and the Project 7 Water Authority. Smaller municipal and domestic sys. terns. such as the City of Gunnison and the Town of Crested Butte, were modeled simply as depletions because of their small size and the spatial and temporal proximity of diversion and return flow points. The modeled operating procedures for the major systems are described briefly below. Aspinall Unit Aspinall operations are represented only by Blue Mesa storage and release policies; Morrow Point and Crystal reservoirs are assumed to operate. from a monthly perspective, as run.of-river facilities with no storage capacity (and, consequently, no evaporation). Blue Mesa releases in January through July are determined by inflow forecasts and releases in August through December are determined from a set of declining storage targets. Both these releases are subject to a minimum power release require- ment which is a function of reservoir contents. After these operations are executed, the model checks to see if a minimum flow of 300 cfs has been achieved in the Black Canyon; if this flow has not been achieved, an additional release is made to bring the minimum up to 300 cfs. The objective of determining releases from forecasts is to obtain as constant a flow regime be- low Crystal Dam as possible while filling Blue Mesa without a spill by the end of]uly. The forecast.based release for the current month is computed using the following equation: release = [(forecast + sideinflow. contents. capacity)/monthsleft] - inflow forecast is the projected inflow from the current date through July sideinflow is the average inflow between Blue Mesa and Crystal for the current month contents is the active contents of Blue Mesa at the begiJ1ning of the current month capacity is .the active capacity of Blue Mesa (829,600 acre.feet) monthsleft is the number of months from the current date through July i.!!t!illY is the Blue Mesa inflow for the current month The objective of defining releases based on declining storage targets is to obtain adequate winter drawdown of Blue Mesa to prevent ice-jam.induced flooding in the Gunnison area and to have adequate space to store the next year's runoff. The storage targets were obtained from the USBR Salt Lake Regional office and are stated in terms of acre-feet of active capacity. The targets used in the model are as follows: July August September 829,600 800,000 750,000 October November December 700,000 650,000 590,000