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18 002254 . The additional water, 1,200,000 acre-feet, required for exchange purposes would be conserved in two storage reservoirs proposed on Trinity River. Helena Reservoir with a gross stor- age capacity of 2,800,000 acre-feet would be built on the main Trinity River downstream from Lewiston Dam. This reservoir would develop an annual new water yield of 600,000 acre-feet which would be diverted to the Sacramento River. Subsequently Eltapom ReseF- voir, with a gross storage capacity of 3,100,000 acre-feet, would be constructed on the South Fork of Trinity River. This reservoir also would develop an annual yield of 600,000 acre-feet which would be diverted to Helena Reservoir with subsequent diversion to Sacramento River. Power generating facilities would be incor- porated with these proposed developments. Estimated capital costs of these reservoirs and associated facilities are $540,000,000. Annual OM&R costs would be offset by power revenues with a net annual amount remaining of about $12,300,000. The estimated total capital cost for this prospective plan, including tunnel diversions and conveyance to Lake Havasu on Colorado River, exchange conveyance facilities, and storage reservoir systems is $1,750,000,000. The annual OM&R and pumping costs are offset by power generated with an estimated annual revenue remaining of $9,900,000. Under this proposal, therefore, the additional 1,200,000 acre- feet of water would be stored and conveyed to Lake Havasu at an estimated average annual equivalent cost of $58 per acre-foot, including interest at 3 percent and amortization of the facilities in 50 years. The average annual acre-foot cost given is computed by using incremental costs of enlargement of part of the California Aqueduct. Appropriate allocation of costs between the California Aqueduct and the proposed incremental enlargement under this plan may reflect some increase in this acre-foot value. . This plan contemplates diversion of water from several east side San Joaquin Valley streams by relatively high elevation tunnels. Since this water is now being used downstream, exchange facilities and water supplies will be required. Approval of these exchanges will require negotiations with the downstream water users. Such negotiations could be both lengthy and complex. The reservoir storage systems and related diversions to Sacramento River proposed under this plan should be authorized for construction and operation by the Bureau of Reclamation as a part of the Pacific Southwest Water Plan even though they will be inte- grated closely with existing and proposed features of the Federal Central Valley Project.