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Description of Existing Model 6 release = (forecast + contents - capacity)/momhslcfl , forecast is the projected inflow from the curn:nt date through July caments is the active contents of Hidgway illlhe beginning of the current month caoacirv is the active capacity of Ridgway (55,000 acre-feet) rnonthsleFt is the number of months from the current date through July The storage targets are used 10 insure adequate drawdown of the reservoir prior to forecasts becoming available. These targets were derived based on discussions with the USBR Salt Lake Regional office; they could not be verified during calibration since there was no historical record of Ridgway op- eration at the time the model was developed. 'The targets used in the model are as follows: March.July August September October 55,000 52,000 49,000 46,000 November December January February 44,000 41,000 40,000 40,000 After estimatmg the release called for by the storage targets, the forecast, or the various demands, the model checks to insure that the minimum release of 30 cfs or inflow (whichever is less) has been satisfied. If it has not, this release or bypass is imposed as the minimum value. Project 7 Water Authority The Project 7 ~fater Authority obtains water supplit:s frolll the: Cimarnm Canal and from the South Canal. The total Project 7 demand in the model is 10,194 af per year. Deliveries from the Cimar- ron are limited to the average yield of shares owned by the CIlY of Momrose. Diversions from the UV. WUA's South Canal make up the rema.ining Project 7 raw water deliveries, with a like amount of water released for irrigation use from the M&I account in Ridgway. Storage of Cimarron Canal and South Canal wJ.ter in Cerro and fairview reservoirs is represented in the model; releases from these reservoirs are made on demand. I, MODEL CALIBRA TJON The model was calibrated against historical data for the years 1979 through 1983. This period was chosen because the gaged flow and storage records for this period reflect current operations rea- sonably well and because it did not require development of additional inflow data beyond that required for other study purposes. Graphical comparisons and correlations were made between historical gaged streamflows and reservoir contents and those predicted by the model. Model parameters relating to simulation of operating procedures and to calculation of return nows were adjusted to achieve closer agreement between modeled and historical results. The c:llibration so a<.:hieved was quite good. CRITICAL REVIEW OF EXISllNG MODEL The criticisms that have been made of the existing model rclate mainly to [he simplifying as- sumptions that were made to permit its development within a limited study budget or (Q the purposes to which it was put (the latter really being criticisms of the study rather than the model). The principal simplifying assumptions m the model arc the following: 1) ccrtain tributary areas of the basin were represented only as net innows and systems in those areas were nOI modeled explicitly, 2) most water rights were aggregated <lnd represented as depictions rather than diversions and return llo\\'s, 3) the model failed. \0 show some shortages that local watcr users hall been experiencing suggesting that in- nows for certain ungagcd basins should he refined, and 4) no user document or manual was produced to assist others in usmg the model. Each of these areas is disclIssed briefly below .