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<br /> <br />Adjusted Historic Study <br /> <br />The approach taken in this routing study, as well as the <br />, 1990 "without project" study which will be explained later, was <br />ideal routing. <br /> <br /> <br />Ideal routing studies may be defined as water routing of <br />the presently unused or future increased flows as high in the <br />basin as possible without regard to existing priorities. <br />Exhibit 4 illustrates the importance of this concept to our studies; <br />it is the basis for all "with project" studies and alternates. <br /> <br />The water supply, as alre,ady explained, is the minimum <br />historic river flow. Demand for the water was the histor:l,.e crop <br />irrigation shortage to allow for farm losses and transportation <br />losses based upon the incremental wetted perimeter due to <br />additional diversions. <br /> <br />Return flows from these incremental diversions were computed, <br />but, because of the insignificant quantities involved, they were <br />not rediverted in the "without project" study. Remaining demand <br />and flow after this minimum flow routing was computed for each <br />ditch heading, and major tributary inflow point. Storable flows <br />at the two reservoir sites were computed in preparation for a <br />"with project" study. <br /> <br />"With Project" <br /> <br />The purpose of the "with project" studies is to determine <br />which of the two sites, Weld Oounty or Narrows, is better hydro- <br />logically for reducing irrigation shortages. Shortages can be <br />reduced in three waysl upstream shortages by exchange, shortages <br />of ditches participating in the project situated below the <br />reservoir by direct reservoir releases, and reduction in shortages <br />for nonparticipating ditches below the reservoir through the <br />opportunity to divert return flows from participating ditch <br />losses. <br /> <br />Exchange <br /> <br />Our exchange studies were accomplished in two steps. Step <br />one was to determine the magnitude of "without project" diversions <br />which could have been made by exchange if a reservoir had been in <br />operation through a process of 'satisfying the three requirements <br />of exchange] (1) junior priority demand above the reservoir, (2) <br />flows available at the point of demand, and (3) the right to the <br /> <br />23 <br />