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<br />III <br />1\ <br />II <br />JI <br />II <br />. <br />. <br />. <br />. <br />.. <br />I <br />I <br />I <br />I <br />I <br />I <br />! <br />I- <br />I <br />\ <br /> <br />- <br /> <br />187i <br /> <br />been irrigated each year with no water transferred out of the Model right and <br />with all winter storage charged to the Model right. Under Case 3, the com- <br />putation shows the difference in the actual inflow as compared to what would <br />have occurred had the same acreage as was actually irrigated in 1979-84 been <br />irrigated, but with no water transferred out of the Model right and with all <br />winter water storage charged to the Model right. <br /> <br />The computat ions used in a 11 three cases were patterned after those used in <br />the 1961 and 1964 studies and utilized the computer model developed for <br />this review. In order to use the computer model, the depletion at the <br />A lf a 1 fa gauge under the actua 1 condit ions was ca 1 cu 1 ated us i ng the <br />following formula (same formula as used in the 1961 and 1964 studies): <br />Depletion at Alfalfa = Headgate requirement + excess diversion - irrigation <br />release shortage + Trinidad Reservoir inflow - Trinidad Reservoir releases <br />- return flow. Actual Trinidad Reservoir inflow and release were used in <br />all three cases. Case 1 computations used irrigated acreages as shown in the <br />Colorado Agricultural Statistics {except 18,386 acres in 19841/)and actual <br />headgate diversions to determine excess irrigation and shortages, whereas <br />Cases 2 and 3 assumed ideal headgate diversion. <br /> <br />Cases 2 and 3 were computed under the assumption that the actual diversions were <br />equal to the headgate requirement. Table 2 shows the computation of headgate <br />requirement, actual headgate diversion, excess diversion, return flow and deple- <br />tion at the Alfalfa Gauge used in Case 1. Table 3 shows the actual headgate <br />diversion, return flow and depletion at the Alfalfa Gauge used in Case 2 and 3. <br /> <br />The values for the depletion at the Alfalfa gauge under Cases 1, 2 and 3 <br />were entered into the computer model. The model calculated the depletion <br />that would have occurred at the Alfalfa gauge had the transfer from the <br />Model right not taken place and had the winter storage been charged to the <br />Model right. The difference in the depletion at the Alfalfa gauge was then <br />run through the channel loss part of the model to determine the impact at <br />John Martin Reservoir. <br /> <br />The annual impacts on the inflow to John Martin Reservoir for Cases I, 2 <br />and 3 are shown in Tab 1 e 4. Month ly summary of resu lt s and more deta i1 on <br />the computations are contained in Appendix II. <br /> <br />During the review period, transmountain water was delivered down the <br />Arkansas Ri ver to John Mart i n Reservoi r in exchange for "out of pri ority" <br />storage of inflow to Trinidad Reservoir (see Chapter IV.H.). Since the com- <br />putations for Cases 1, 2 and 3 used actual Trinidad Reservoir inflow, the <br />impact on the inflow to John Martin Reservoir must be adjusted for the <br />exchange. These adjustments are also shown in Table 4. <br /> <br />lhhe Colorado agricultural statistics on irrigated land include some lands out- <br />side the project area. These statistics reported 21,400 acres irrigated in <br />1984 whereas Bureau of Reclamation field survey found the maximum project lands <br />irrigated during the review period to be 18,386 acres (see Chapter IV.D.I.). <br /> <br />13 <br />