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003141 ", SYNOPSIS report on the Colorado River Storage project and participating projects. The D plans, notwithstanding their greater over-all cost, would not be excluded oy thi8 0rite~~on, Interesting 8CO.lnru.CC comparisons between the large projects and the small projects are noted in Table I. With hydraulic pumping (D plans), the large projects have slightly lower over-all costs per acre and con- sequentlyhigher benefit-cost ratios than small projects. The large projects ,with about triple the irrigated acreage, have substantially higher net benefits (benefits in excess of costs),' With electric pumping (E plans), the large projects have slightly higher over-all costs per acre and lower benefit-cost ratios, but far higher net benefits than the small projects. The comparisons in Table I are based on amortizing construction costs over a 100-year period at 2'.5-percent intereat. If a shorter. period or a higher interest rate were assumed, the comparisons would be even more favorable to the E plans. The analyses indicate that the South San Juan project Would be economically justifiable and that the relative justifi- ability would be substantially the same for any size of development ranging from about 20,000 acres up to the limits of the availabl~ water supply. .. If the South San duan project were limited to the irrigation of lands outside the Navajo Indian Reservation that can be served by gravity flow from the Shiprock project canal, it would serve only about 2,270 acres. The added cost of constructing the Shiprock project facilities large enough to irrigate these lands probably would not exceed $750 an acre, and the added annual 0peration and maintenance cost is estimated at about $1.25 an acre. Both of these costs are materially less than cor- responding costs for any of the larger plans that would require pumping. The Hammond project that would divert the natural flow of the San Juan River to irrigate 3,670 acres of land on the south side ,0f the river near Bloomfield, N. Mex., has beeD recommended for authorization as a participating project with the Colorado River Storage project. As an alternative, the Hammond project lands also might be served by an enlargement of the Shiprock project canal. The desirability of this alternative has not been investigated but should receive attention in future studies. .. Authorization to construct a dam and power plant on the San Juan River at the Navajo site as a unit of the Colorado River Storage project :was recollllllE>nded in the December 1950 report previously mentioned. The unit was intended for power prOduction and to assure deliveries of Colorado River water at Lee Ferry as required by the Colorado River Compact. The report menti'ltled possible need of the storage site .for irrigation of lands in the San Juan Basin and cited a provision J,n the Upper Colorado River Basin Compact of 1946 providing that if such need iv