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<br />Ouij47 <br /> <br />Task 1.14(b) - Consumptive Use Prototype Development <br /> <br />~.vV/ <br /> <br />sa = maximum surface area (L 2) <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 stock pond to obtain the total <br />consumptive use. <br /> <br />The average surface area of the stock pond is adjusted from the maximum surface <br />area by using a fullness factor. This factor depends on the location and elevation of the <br />stock pond. The evaporation can be represented by free ~face evaporation (FWS) <br />rate or by a representative pan evaporation that alread~d~the pop coefficient. - 7. <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 100 percent <br />effective. <br /> <br />The above methodology allows the user to be overly detailed in his approach for <br />computing the stock pond consumptive use, i.e., identifying each and every stock pond <br />in the area and computing each water loss separately. However, considering the small <br />amount of water use from stock ponds, the subroutine can also accept a single aggregate <br />value for the area being considered and compute for the aggregate consumptive use for <br />that area. This is useful particularly when the data required for computing consumptive <br />use from each stock pond are not available. <br /> <br />2.7 CU Methods for Livestock <br /> <br /> <br />2.7.1 Develop Methodology <br /> <br />Livestock consumptive use is an estimate of water use of all animals of considered <br />types of livestock in a given area. It is estimated from the average use rate by the animal <br />and their number in a given area. <br /> <br />2.7.2 Develop and Implement Subroutine <br /> <br />The methodology for estimating consumptive use of livestock is implemented in a <br />FORTRAN subroutine. The subroutine can be called by a main program to compute for <br />the consumptive use of any number of animals of any types (considered significant) of <br />livestock in a given area for any period of time (daily, biweekly, monthly, yearly, etc.). <br /> <br />The equation that is used is: <br /> <br />cu = n * c --- for all types <br /> <br />where cu = consumptive use (L3) <br /> <br />n = number of animals in the given area <br /> <br />c = average use rate per animal of each type during the <br /> <br />time period (L3) <br /> <br />7/13/94 - Draft of Task Memorandum <br /> <br />11 <br /> <br />IDS Group, CSU <br />