CHAPTER II. PLAN OF DEVELOPMENT The Colorado River storage project would provide the longtime regulatory storage needed to permit States of the upper division to meet their flow obligation at Lee Ferry, as defined in article III (d) of the Colorado River compact, and still utilize their apportioned water. During periods of low streamflow, the States would release storage water to meet the Lee Ferry flow obligation and in exchange they would divert upstream flow for use in the upper basin. The project would provide some storage water for direct use in the upper basin. In addition, the project would control sediment, abate floods, facilitate recreational development, and aid in fish and wildlife conservation. It also would permit production of a substantial amount of the electric energy needed in the upper basin and adjacent areas. Revenues from the sale of project-generated power would be sufficient to pay all reimbursable Colorado River storage project costs and to assist irrigators in payment of costs of other projects that would utilize waters of the upper Colorado River system. Project works COLORADO RIVER STORAGE PROJECT Eight major storage dams and two high dams providing only minor storage would be constructed on the Colorado River and its principal tributaries above Lee Ferry. The reservoirs formed by the dams would have a total capacity of 48,555,000 acre-feet. Powerplants and other appurtenant facilities would be provided at each dam and necessary transmission lines would be built. The highest dam and the one creating more initial storage capacity than all others combined would be the Glen Canyon Dam of the Glen Canyon unit. This dam, only 17 miles upstream from Lee Ferry, would be a key structure in controlling water releases to the lower basin and in impounding the heavy silt accumulations which enter the river in the southern part of the upper basin. It is the only dam planned on the upper Colorado River proper. Four of the dams would be on the Green River. In order, moving upstream, these would be the Gray Canyon Dam of the Gray Canyon unit, Split Mountain Dam of the Split Mountain unit, Echo Park Dam of the Echo Park unit, and the Ashley Dam of the Flaming Gorge unit. The Split Mountain Dam would provide no active storage capacity and would be useful primarily for power generation, with stream regulation provided by the Echo Park Dam only 21 river miles upstream. The Echo Park Dam, located 3 river miles below the junction of the Green and Yampa Rivers, would back water up both streams, creating the system's second largest reservoir. Echo Park on the Yampa River would be the Cross Mountain Dam. The Whitewater Dam of the Whitewater unit would be located on the Gunnison River 15 river-miles above Grand Junction, Colo. Above the Whitewater Dam would be Crystal Dam of the Crystal unit which would have limited storage and the Blue Mesa Dam of the Curecanti unit which would provide storage regulation for its own and the Crystal powerplants. The Navaho Dam of the Navaho unit would be located on the San Juan River about 19.5 river-miles upstream from Blanco, N. Mex. Locations of the potential project units are shown on the accompanying profile. The profile also shows the locations of existing and potential developments in the lower basin. Detailed data on the structures included in the various project units are given in Chapter III-Designs and Estimates. Regulatory storage A capacity of 23 million acre-feet would be reserved in project reservoirs for long-time regulatory storage. The water stored would be released as needed in drought periods to meet the compact obligation at Lee Ferry. The reservoirs would be refilled during years of favorable water supply. In a dry decade such as that of 1931-40, release of the entire 23 million acre-feet would be necessary to meet the Lee Ferry obligation. A storage release in that amount would be necessary even if water uses in the upper basin were naturally curtailed by the drought, resulting in a depletion at Lee Ferry somewhat less than the compact-permitted 7,500,000 acre-feet annually. Present flows in the upper basin are adequate to meet the 10-year Lee Ferry obligation. Within 20 or 25 years, however, the depletions are expected to increase to the extent that curtailment of consumptive uses will be necessary in protracted dry periods unless some storage water is available for delivery to the lower basin. If the required storage works are to be available when needed, steps toward construction should be taken immediately. An extended construction period will be required and the reservoirs should be filled initially while unused apportioned water is available. The amount of storage capacity, if any, required for assistance in the administration of the Mexican Water Treaty cannot be determined at this time. The plan outlined herein does not provide for, nor preclude, storage for this purpose. It is assumed, however, that any additional water required at Lee Ferry for Mexican use will be made available by applying the principles of curtailment outlined in article IV of the upper Colorado River Basin compact. Irrigation and other water-consuming uses Reservoirs planned for the Colorado River storage project would be located too low on the streams to provide water directly to major segments of lands and to industrial centers in the upper basin. In some instances, however, direct uses would be possible. At the Flaming Gorge Reservoir, for instance, an inactive storage pool of almost a million acre-feet would be maintained to permit a gravity diversion to the Uinta Basin as contemplated under the central Utah project. Also, a considerable amount of active capacity in the reservoir would be provided for regulation of the water reserved for direct diversion. As an alternative, water for the Uinta Basin could be provided by pumping from Echo Park Reservoir. Gunnison River water could be diverted from Whitewater Reservoir above an inactive storage pool of 410,000 acre-feet and conveyed to Grand Valley to replace water now provided from the Colorado River. In exchange, the Colorado River water would become available to potential upstream develop ments including export diversions. Active capacity in the Whitewater Reservoir would be required to provide regulation for the replacement diversion. The entire active capacity of the Navaho Reservoir would eventually be required to regulate San Juan River water for potential developments both upstream and downstream on the San Juan River. Water from the Navaho Reservoir could directly supply the Shiprock project (Indian), the South San Juan project, or by exchange it could benefit possible projects for the exportation of water to the Rio Grande River Basin in Colorado and New Mexico. Capacities in the Flaming Gorge, Whitewater, and Navaho Reservoirs reserved to regulate water for use in the upper basin, if not required immediately for that purpose, could serve in the interim to facilitate the generation of electric energy. As additional investigations are made, it may be found desirable to use other Colorado River storage project reservoirs to store water for irrigation and other consumptive uses in the States of the upper division. Preference to the use of reservoirs for such storage is given in article V (b) of the upper Colorado River Basin compact over the use of reservoirs for assurance of deliveries at Lee Ferry. Sediment control A total capacity of about 20 million acre-feet would be provided in project reservoirs to accommodate the sediment that would be deposited in a period of 200 years. With reduced erosion of the watersheds by improved practices of land management agencies, the period of protection against sediment encroachment would be extended. In the future it may also be desirable to develop other sediment storage sites in the upper basin. More than three-fourths of the sediment in the river will enter the river below all potential reservoirs except Glen Canyon. Fortunately, ample sediment storage capacity can be economically developed in the Glen Canyon Reservoir to protect present and future reservoirs in the lower basin from sediment encroachment. Next largest capacities for sediment retention would be provided at the Flaming Gorge and Gray Canyon Reservoirs on the Green River. A part of the sediment would be carried into the lower levels of the reservoirs where it would occupy inactive reservoir capacity. The major part, however, would settle in shallower reservoir areas and reduce the active capacity useful for other purposes. Power production Powerplants would be installed as project features to utilize the regulated river flows and the hydrostatic heads at project dams for the generation of electric energy. The plants would have a total generating capacity of 1,622,000 kilowatts. Initially, with all the units in coordinated operation, they would have a firm annual output of about 9 billion kilowatt-hours and with ultimate development in the upper basin they would have a firm annual output of about 6 billion kilowatthours. Hydrostatic heads at the dams would vary with changes in reservoir content. Minimum power pool elevations, however, would be maintained at project reservoirs. To aid in creating power heads a minimum inactive capacity of about 11 million acre-feet would initially be provided. Although more than 8 million acre-feet of this capacity |