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<br />07/09/2034 12:51 <br /> <br />:fl025'31:l/!::J1:l <br /> <br />W~lbHI WAI~~ ~Nb lN0 <br /> <br />t-'A\:lt.. tN <br /> <br />u01795 <br /> <br />Conclusions <br /> <br />The La Plata River is a highly over-appropriated stream that has limited water supplies to meet demands <br />by both Colorado and New Mexico water users. River bottom or alluvial geology, an arid climate, and <br />extensive riparian native vegetation all act in concert to consmne a scarcity of water supply - particularly <br />during the times of heightened need during the irrigation season in a drought year. Although the La Plata <br />River has tlrree sources of tributary inflow and incremental irrigation retmn flows, there is insufficient <br />native streamflow to sustain a live stream at several locations along the 30.9 river-mile corridor between <br />the Hesperus Gage and the stateline. Phreatophytes inundate 1168 acres upstream of the confluence with <br />Long Hollow up to the Hay Gulch Ditch. The following table illustrates the average amount of water <br />each of the six river reaches would consume in both monthly volwne and daily flow requirements. <br /> <br />Average Daily Consumptive Use <br />(acre-feet) <br /> <br /> Reach 1 Reach 2 Reach 3 Reach 4 Reach 5 Reach 6 rotal (Ac-Ft) Flow (cfs) <br />May 21.9 9.3 17.7 9.7 5.4 6.9 71.0 35.8 <br />June 36.5 15.6 29.5 16.2 9.0 11.5 118.3 59.7 <br />July 46.3 19.7 37.4 20.5 11.4 14.5 149.9 75.6 <br />August 39.0 16.6 31.5 17.3 9.6 12.2 126.2 63.6 <br />September 24.3 lOA 19.7 10.8 6.0 7.7 78.9 39.8 <br />October 17.0 7.3 13.8 7.5 4.2 5.4 55.2 27.8 <br /> <br />During the month of August, results of a Blaney-Criddle analysis indicate that a base streamflow of 63.6 <br />cfs is necessary to meet the evapotranspiration needs of riparian vegetation. In conservative terms, it is <br />reasonable to assume that residual groundwater from declining alluvial water tables and an accepted level <br />of analytical error may reduce the amount of streamflow requirements by half or even up to 75 percent. <br />Accepting those premises at face value would decrease the daily native vegetation consumptive use <br />demand in August to 31.8 and 15.9 cfs respectively. It is important to note that these conservative <br />assumptions still place the demand by riparian phreatophytes well above the measured daily average <br />streamflow of 10.9 cfs at Hesperus. Invoking the futile call doctrine to cease the wasting of water by <br />attempting to run it through a dry river channel that is encroached upon by thirst phreatophytes in the <br />summer of 2000 was a proper and defensible decision. <br /> <br />3 <br />