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<br />'6liiJ50 <br /> <br />Task 1;14(b) - Consumptive Use Prototype Development <br /> <br />cu = sa · (ff' ep - cf' rf) --- for all reservoirs <br /> <br />where cu = consumptive use (L3) <br /> <br />sa = maximum surface area (L2) <br /> <br />ep = evaporation during the time period (L) <br /> <br />rf = total rainfall during the time period or salvage value (L) <br /> <br />ff = fullness factor (dimensionless) <br /> <br />cf = coefficient (dimensionless) <br /> <br />The above equation is repeatedly used for each reservoir to obtain the total <br />consumptive use. <br /> <br />The average surface area of the reservoir is adjusted from the maximum surface area <br />by llsing a fullness factor. This factor depends on the location, elevation and purpose <br />(irrigation, municipal and industrial, fish and wildlife). For measured reservoirs, the <br />actual surface area is available and thus, the fullness factor is assumed equal to unity. <br /> <br />The evaporation can be represented by free water surface evaporation (FWS) rate or <br />by a representative pan evaporation that alread~cou~he pan coefficient. <br /> <br />The net consumptive use is obtained by taking into account effective rainfall or <br />salvage value whichever is lesser. The coefficient accounts for the actual surface area <br />(fullness factor) and the effectiveness of rainfall (cf = 1.0 for salvage value). Since this <br />data is not currently available, a default coefficient value equal to the fullness factor is <br />assumed. This translates into another assumption that the total rainfall is lOO percent <br />effective. <br /> <br />7 <br /> <br />3.0 Conclusions and Recommendations <br /> <br />During May and June a firm foundation was built for the design and implementation of the <br />Consumptive Use Model. All of the modeling components have been identified and <br />coordination with the overall progress with CROSS has been successful. The technical <br />methodology has been established for all the consumptive use categories and the data <br />requirements have been identified. <br /> <br />7/13/94 - Draft of Task Memorandum <br /> <br />14 <br /> <br />IDS Group, CSU <br />