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<br /> <br />. <br /> <br />...... <br />~ <br />""" <br />(/) <br /> <br />. <br /> <br />. <br /> <br />EVALUATIONS OF EXISTING SALINIIT COh1JITIONS <br /> <br />than using the 1974 historical evaportion since a single year record <br />could show an above-ar-below normal condition. Present evaporation of <br />the Lower Basin Reservoirs was assumed the same as historical since <br />these reservoirs have been operating for a number of years. <br /> <br />Historical flows since 1941 have been affected by the transmounta~n <br />diversions of the Colorado-Big Thompson Project, Duchesne Tunnel of <br />Provo River Project, Roberts Tunnel of the city of Denver, and a number <br />of small in-basin developments in the Upper Basin. More recently the <br />Independence Pass expansion, Collbran, Paonia, Smith Fork, Silt, Florida, <br />Hammond, Bostwick Park, San Juan-Chama, and Emery County Projects and <br />Vernal Unit of Central Utah Project have come into operation. Also, as <br />previously mentioned evaporation from the Colorado River Storage Project <br />Reservoirs, ~avajo, and Fontenelle Reservoirs is now in effect along <br />with the Hayden Powerplant, Four Corners Powerplant. expansion of Hogback <br />Indian lands. and the municipal and industrial uses in Wyoming. In the <br />Lower Basin. corrections have been made for the Southern Nevada Water <br />Project, the Metropolitan Water District diversion at Lake Havasu. the <br />Colorado River Indian Reservation, and the Palo Verde Irrigation District. <br />The depletions from all of the above projects have been extended back to <br />1941, from the time they became operational, so that when increased <br />depletions on existing project or new depletions on new projects occur <br />they can be imposed directly on the present modified condition to show <br />the anticipated effect of all development on the river. In the near <br />future several projects now under construction will become operational. <br />The addition of these new depletions will result in slight increases in <br />dissolved-solids concentrations under present modified conditions. <br /> <br />Quality data for present modified conditions were computed by <br />taking into consideration (1) the flow weighted average of the concentrations <br />of total dissolved solids for the various transmountain diversions. (2) <br />the change in dissolved solids resulting from the existing upper in- <br />basin developments on the basis of an assumed pickup of 2.0 tons of <br />dissolved solids per acre of irrigated land and a depletion of 1.5 acre- <br />feet of water per irrigated acre, and (3) in the Lower Basin a consumptive <br />use of 4 acre-feet per acre and a 2.0 tons per acre pickup for irrigation <br />of the Palo Verde Irrigation District, the Fort Mohave. Chemehuevi, and <br />Colorado River Indian lands. The value of 4 acre-feet per acre is the <br />rate presented in the Colorado River Basin Project hearings before the <br />Subcommittee on Irrigation and Reclamation of the Committee on Interior <br />and Insular Affairs, House of Representatives. <br /> <br />The present modified conditions are shown on Table E and are used <br />as a base value for developing the anticipated effect of new depletions <br />from new projects and the full development of present partially developed <br />projects in the river basin. <br /> <br />Following is a brief description of the large existing dams and <br />reservoirs on the Colorado River. <br /> <br />45 <br />