C150315 Feasibility Study - Laserfiche WebLink

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MODEL OPERATIONAL SCENARIOS SUPPLY SIDE SCENARIOS The Supply Side Scenario (SS Scenario) model for Snowmass Creek operates the District's water rights as well as the downstream (non-District) water rights based on their relative priority and decreed amounts. The model determines the maximum flow legally and physically available from Snowmass Creek under the District's municipal water rights. The District's water rights that have not been transferred to or decreed for municipal uses were excluded from the model. Water calls from the main stem of the Roaring Fork River and the Colorado River are not modeled. The following three Supply Side Scenarios were initially used to account for non- District diversions on Snowmass Creek that can reduce the diversions of or call out the District's water rights in times of stream flow shortage: 1. Historic Dry Year Non-District Diversions; 2. Average Monthly Non-District Diversions; and 3. Maximum Monthly Non-District Diversions. At the District's direction, Wheeler has only included Maximum Non-District Diversions (Maximum Diversion) in the results and discussion sections of this memorandum. A detailed description of this scenario is provided in the following paragraph. Maximum Monthly Non-District Diversions. The Maximum Non-District Diversions is based on the monthly diversion records at each Snowmass Creek structure for the 1990 — 2004 period. The maximum historic diversions at each structure for each month (i.e. in June) were determined using data obtained from Colorado State Decision Support System's HydroBase database. These diversion rates are used as a maximum diversion limit for each diversion structure. The maximum historic diversions at each structure were distributed among the water rights that divert at said structure starting with the most senior and working toward the junior. The Maximum Diversion amounts Page 14