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<br />G03202 <br /> <br />. <br /> <br />Additional surface reservoir sites, on stream or off stream, are <br /> <br /> <br />essentially nonexistent in the study reach and therefore do not provide <br /> <br /> <br />a viable solution to reducing the stream outflow during the winter months. <br /> <br /> <br />It seems obvious that the ground-water reservoir offers the most potential <br /> <br />for regulating the outflow during the non-compact periods. It may be <br /> <br /> <br />possible, by reducing the deep percolation from canals and irrigated fields <br /> <br /> <br />at specific locations to reduce the amount of return flow reaching the <br /> <br /> <br />river in the winter months. It also may be possible to meet more of the <br /> <br /> <br />crop irrigation requirements from ground water in below-average surface- <br /> <br /> <br />water years rather than placing calls on upstream junior rights to bypass <br /> <br /> <br />water, then use winter flows to replenish the ground-water storage, <br /> <br /> <br />The second item, phreatophyte consumptive use, is a sizable loss of <br /> <br /> <br />water particularly when one realizes that it has an impact on the avail- <br /> <br /> <br />ability of water at the very times the crop irrigation requirements are <br /> <br /> <br />highest, The reduction in streamflow during a hot July or August day by <br /> <br /> <br />the evapotranspiration losses from high water table and phreatophyte areas <br /> <br /> <br />probably exceeds 200 cfs. Control of the water table and phreatophytic <br /> <br /> <br />growth is admittedly quite controversial and it is beyond the scope of <br /> <br /> <br />this study to get into that aspect of the efficiency picture. <br /> <br /> <br />The flow at Julesburg during the period April 1 to October 15 is sub- <br /> <br /> <br />ject to the Colorado-Nebraska Compact- As mentioned earlier, the compact <br /> <br />functions as a call on the river during this 6-1/2 month period whenever <br /> <br /> <br />the flow at Julesburg is less than 120 cfs. Table 8 shows the number of <br /> <br /> <br />days per week during the l5-year study period that the Julesburg flow <br /> <br />was less than 120 cfs. It can be seen that the Compact "call" was on <br /> <br /> <br />over 90 percent of the time during the dry years of 1954 and 1956. <br /> <br /> <br />Obviously, it is years like 1954 and 1956 that additional ground-water <br /> <br /> <br />use in the study reach would be desirable--but could further reduce the <br /> <br /> <br />flow at Julesburg. <br /> <br />. <br /> <br />. <br /> <br />-45- <br />