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Conclusions <br />As shown in Table 1, in most cases the baseflows calculated using the variable efficiency and <br />soil moisture accounting algorithm have a lower annual flow than the original baseflow <br />calculations. This means that on the average for these reaches, less diverted water is consumed <br />and more water is returning to the river. StateMod does not currently produce a report showing <br />estimated soil storage during the baseflow calculation. However, water is not withdrawn from <br />the soil reservoir during baseflow simulation to satisfy irrigation water requirement, it is <br />withdrawn only to satisfy a headgate demand. Therefore, during baseflows simulation, the soil <br />moisture is likely having an unmeasurable effect on the results. <br />The baseflow locations higher in the watershed, with relatively few upstream irrigation <br />diversions, show the smallest decreases in baseflows and in some cases, such as the Elk River at <br />Clark gage; included in Table 1, show an increase in baseflows. This particular gage has fewer <br />than 12 small diversions upstream. The slight increase in baseflows likely reflects the relative <br />abundance of water on that tributary, and the irrigation practice of diverting water based on <br />availability not necessarily on crop needs. The consumptive use analysis further confirms this, <br />with estimates of average annual shortages in that drainage of around 6 percent, which is lower <br />than other tributaries of the Yampa River. <br />The difference in baseflows calculated during the CRDSS efforts and the new baseflows <br />calculated using the variable efficiency and soil moisture accounting algorithm are, on the <br />average, not significant. However, in months when supplies are more abundant or short, the <br />differences are important. These months are generally the critical months for investigating the <br />potential for future supplies or the effects of low flows on endangered species. Because the new <br />baseflows more accurately account for water use and common irrigation practices in the Yampa <br />River Basin, they are recommended to be used in subsequent model simulations. <br />Comments and Concerns <br />None. <br />L:ASecrion Folders\SECD\Carolyn\CDSS\VariableEff Taskl-3.doc 12 of 16 <br />