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<br />. <br /> <br />. <br /> <br /> <br />. <br /> <br />.r r.... (o, ,rh, <br />1 u.\) <br /> <br /> <br />flows at this gauge shall not be depleted by Project operations. <br /> <br />Published records are available for the Trinidad gauge, which is on the Purgatoire River <br /> <br />just upstream of the first Project diversion and the Thatcher gauge which is downstream of the <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 period of record, <br /> <br />the 10 year period prior to Project operations and the 10 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 diagram and is a small decrease, approximately 3 per cent, in depletions in <br /> <br />the Project area (Appendix E). These effects can essentially be attributed to Project operations <br /> <br />since the effects of tributary flows are assumed to be the same as the 10 year period prior to the <br /> <br />Project, as in the 10 year review period. The tributary effects of the two periods can be assumed <br /> <br />to be the same because tributary flows in the Project area are a factor of area precipitation and the <br /> <br />average water year precipitation at the Trinidad airport for the pre-Project 10 year period and the <br /> <br />10 year review period was 14.02 and 14.16 inches respectively or a difference of about 1.0 <br /> <br />percent. <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 />23 <br />