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<br />. <br /> <br />. <br /> <br />. <br /> <br />1 j ""'I ."'" <br />'* , .:. <br /> <br />last point of return flow from Project lands, for the period 1967 through 1994 which includes a <br /> <br />period of 10 years prior to Trinidad Dam and a 15 year period of Project operations. A double <br /> <br />mass diagram of the Trinidad gauge versus Thatcher gauge was prepared for the pe~od ofr~cord, <br /> <br />the 10 year period prior to Project operations and the 1.0 year review period, The double mass <br /> <br />diagram shows that for the 10 year review period prior to Trinidad Dam, the flow passing the <br /> <br />Thatcher gauge was 71.36 per cent of the flow passing the Trinidad gauge, The double mass <br /> <br />diagram also shows that for the 10 year period of this review, November I, 1984 through October <br /> <br />31, 1994, the flow passing the Thatcher gauge was 74.31 per cent of the flow at the Trinidad <br /> <br />gauge, This minor change is reflected in the double mass diagram as a steeper slope in the trend <br /> <br />line of the double mass and is a'small decrease, approxi~ately 3 per cenZin depletio;i~ th~ ~. <br /> <br />Project area (Appendix E). These effects can be attributed to Project operations since the effects <br /> <br />of tributary flows are assumed to be the same as the 10 year period prior to the Project, as in the <br />----------. G:AAJ'^->..., <br />1.,9 year review period. The tributary effects of the two periods can be assumed to be the same '1'-_.__: b.( ,.,., <br />~~~ <br />because tributary flows in the Project area are a factor of area precipitation and the a::.erage water ~,,~ <br /> <br />year precipitation at the Trinidad airport for the pre-Project 10 year period and the 10 year review ~ ~ <br />~1> <br /> <br />period was 14.02 and 14.16 inches respectively. <br />.' <br /> <br />In addition to the irrigation depletion, the Project caused an additional depletion of water <br /> <br />at the Trinidad gauge equal to the net evaporation from Trinidad Reservoir. The total gross <br /> <br />evaporation from the reservoir since January I, 1978 through December 31, 1994 has been 49273 <br /> <br />acre feet. The net evaporation or depletion is the gross evaporation less the historical <br /> <br />~ <br /> <br />~"'" <br /> <br />consumptive use of the lands inundated by Trinidad Reservoir. The net evaporation has been <br /> <br />determined to be 66.83 per cent of the gross evaporation or 32930 acre feet from January I, 1978 <br /> <br />22 <br />