cluding annual shortages of more than 25 percent of requirements in 11 years, and more than 75 percent of requirements in each of 2 consecutive years. The studies with Falcon Dam only, also indicate that in years of above normal runoff during a 59-year period like that of record, a total of 17,200,000 acre-feet of U.S. waters originating above the Amistad site would waste to the gulf, or otherwise be lost, an average of 290,000 acre-feet annually. The 17,200,000 here referred to is also revised from amount shown in Project Report dated September 1958, Senate Document 65, 86th Congress, 1st session, to include more recent data. Urgent need therefore exists from the viewpoint of the United States to join with Mexico in construction of additional international storage works on the Rio Grande as provided for in the 1944 water treaty for control of floods and for optimum feasible conservation and regulation of the flow of the river. PROPOSED AMISTAD DAM AND RESERVOIR Article 5 of the 1944 water treaty further provided that in planning the construction of international storage dams on the Rio Grande the Commission shall determine (a) The most feasible sites; (b) The maximum feasible reservoir capacity at each site; (c) The conservation capacity required by each country at each site, taking into consideration the amount and regimen of its allotment of water and its contemplated uses; (d) The capacity required for retention of silt; (e) The capacity required for flood control. The joint planning for a second major international dam was undertaken by the two sections of the Commission soon after ratification of the treaty, and concurrently with the planning for Falcon Dam. In addition to the engineers of the two sections, technical advisers participated in the investigations and planning, including, for the United States, engineers of the Bureau of Reclamation and of the Corps of Engineers, and eminent private consultants; and for Mexico, engineers of the Ministry of Hydraulic Resources. The joint findings by the Commission set forth in its minute No. 207, dated June 19, 1958, are that: (a) The Amistad site located 12 miles upstream from Del Rio, Tex., and 1 mile downstream from the mouth of the Devils River, is the most favorable of the many sites investigated upstream from Falcon Dam, for a second major international storage dam for flood control and conservation of waters; (b) on the basis of the preliminary studies, the following capacities would be required at the Amistad site to provide, in combination with Falcon Reservoir, optimum feasible control of floods and conservation and regulation of waters belonging to each country above Falcon Dam: Proposed Amistad Reservoir storage capacity Flood control_. Conservation and silt storage: Storage capacity (c) a concrete gravity structure with gated spillway, all in the channel section flanked by earth embankments, would be the most suitable type of construction for a dam to provide the proposed reservoir capacity. The proposed dam to provide the reservoir capacity of 5,660,000 acre-feet would be 253 feet in height above the river bed and would have a total axial length of 6.5 miles. The dam would create a lake which, at maximum flow line, would extend 82 miles upstream along the Rio Grande, 15 miles upstream along the Devils River and 17 miles along the Pecos River. A total of 87,400 acres would be inundated at maximum flow level. In the channel portion of the site, there would be constructed a concrete gravity section 2,154 feet long at the crest. This section. would be flanked by earth embankments, one on the Mexican side 4.1 miles long, and on the United States side 2 miles long. The dam structure would require about 1.3 million cubic yards of concrete and 11.9 million cubic yards of earthwork. A paved highway 26 feet in width would be provided along the crest of the dam which could be used for an international crossing if the two Governments desire The concrete channel section of the dam would be triangular shaped with a base about 200 feet in length, and include a 1,070-foot gated overflow spillway to consist of eighteen 50-foot gates to permit a maximum spill of 1,550,000 cubic feet per second. Irrigation outlets would be provided on each side of the concrete section at an elevation which could essentially empty the reservoir, and they would have a total capacity of 12,000 cubic feet per second with storage of 200,000 acrefeet. The concrete section would include a service bridge over the spillway section, and elevator and stairways to reach the galleries, adits, and gate operating chambers. To enable optimum development of the hydroelectric power potential at the Amistad site, preliminary plans provide for steel penstocks in each of the nonoverflow sections of the concrete gravity part of the structure. The earth embankment sections would have a width of 35 feet at crest elevation with downstream slope of 2:1 and upstream slopes of 212:1 and 3:1. The embankment would consist of an inner zone, or core, of impervious materials, flanked by transition zones of semipervious materials, covered by outer zones of free draining materials. Field investigations developed that there are ample materials in the vicinity of the site of adequate quality both for concrete aggregate and for the earth embankments. There would have to be acquired rights-of-way for lands on the U.S. side totaling 56,600 acres, most of which will be confined to the generally steep-walled channel of the Rio Grande and the bottoms of the canyonlike tributary and arroyo channels. Remaining lands are largely being used for sheep grazing. About five ranch headquarters are located in the reservoir site. Only 25 or 30 acres of arable lands would be submerged. Two small hydroelectric powerplants of 1,500 and 2,000 kilowatts on the Devils River, and a steam electric plant of 7,500 kilowatts on the same river, would be inundated. Preliminary findings, subject to revision, indicate that there will have to be relocated about 211⁄2 miles of U.S. highways, about 5 miles. of country roads, 29 miles of Southern Pacific railroad, about 16 miles of telephone trunkline, and the raising or relocation of several miles of transmission lines. The Bureau of Sport Fisheries and Wildlife, U.S. Fish and Wildlife Service, and National Park Service, recommend access and spur roads with parking and picnic facilities for 5 areas on the U.S. shore of the proposed reservoir. FLOOD CONTROL AND CONSERVATION BENEFITS The proposed flood control storage capacity at the Amistad Dam would permit control of all floods of record, including the 1954 flood, to the extent that the maximum rate of release would not exceed 100,000 cubic feet per second. Such control would practically eliminate the threat of flood damages to the cities of Del Rio, Eagle Pass, and Laredo in the United States, the neighboring cities in Mexico and rural developments in the middle section. In addition, spills at Falcon Dam, if any, would be reduced to rates less than 20,000 cubic feet per second so that damages from this source would be practically eliminated. Of the estimated total flood damages to U.S. properties which may be anticipated under existing conditions of development, amounting to $1,864,000, it is estimated that the proposed Amistad Dam would enable the saving of all but $3,000 annually, and hence would result in flood benefits to the United States alone estimated to amount to $1,861,000 annually. The foregoing $1,864,000 and $1,861,000 are revisions of amounts shown in Project Report dated September 1958, Senate Document No. 65, 86th Congress, 1st session to include more recent data. The total conservation storage capacity proposed at the proposed Amistad Dam for the two countries, amounting to 3 million acre-feet, would, in combination with Falcon Reservoir, permit essentially the optimum feasible regulation of the waters of the Rio Grande for each country within the limits of its specified water allotments as provided by the treaty. The U.S. share of storage at the Amistad Dam, amounting to 1,686,000 acre-feet, or 56.2 percent of the total conservation capacity, would, in combination with this country's share of the conservation storage in Falcon Reservoir (1,220,000 acre-feet), permit reduction in U.S. spills at Falcon Dam and wastes to the Gulf from an average of 190,000 acre-feet annually to less than 9,000 acre-feet annually. The foregoing average of 190,000 acre-feet is a revision of amount shown in Project Report dated September 1958, Senate Document No. 65, 86th Congress, 1st session, to include more recent data. Assuming that authorities of the State of Texas will prohibit increase in its water demands from the Rio Grande below Fort Quitman, in order that such additional waters as may be made available by a dam at the Amistad site would be used to firm up the supply for existing demands, the additional regulated supply for the United States, over that with Falcon alone, is estimated to average about 86,000 acrefeet annually. Such quantity would reduce irrigation shortages with Falcon alone by nearly 50 percent. The value of such quantity of water is estimated to amount to $1,892,000 annually. The silt storage capacity proposed at the Amistad Dam, amounting to 550,000 acre-feet, would be sufficient to retain all silt entering the reservoir, over a 50-year period. It would also prolong the life of the silt storage capacity at Falcon and hence the conservation storage capacity of that reservoir beyond the original design of 50 years. COST OF DAM AND RESERVOIR TO THE UNITED STATES The treaty further provides in article 5: The cost of construction, operation, and maintenance of each of the international storage dams shall be prorated between the two Governments in proportion to the capacity allotted to each country for conservation purposes in the reservoir at such dam. On the basis of the contemplated division between the two countries of conservation storage, the total cost of construction, operation, and maintenance of the dam would be divided 56.2 percent to the United States and 43.8 percent to Mexico. Each country would bear the costs of lands and appurtenant works required in its territory, including acquisition of lands needed for the dam and reservoir, damages, relocation of railways, highways, and utilities, construction camps, and access roads. The total cost of the dam and related works to the United States and Mexico is estimated to amount to $79,120,000-revision of amount shown in Project Report dated September 1958, Senate Document No. 65, 86th Congress, 1st session, to include more recent data on the basis of price levels as of January 1960, divided between the dam, penstocks, and related works as follows: Dam___ Penstocks_ Related works. Total__ Total estimated cost, United States and Mexico 1 Revision of amounts shown in Project Report dated September 1958, S. Doc. 65, 86th Cong., 1st sess., to include more recent data. The U.S. estimated share of the construction costs would be approximately as follows: Less present worth of terminal land salvage after 50 years_ Subtotal_. Total____ 1 Estimated $26, 870, 000 57, 079, 000 450, 000 1 56, 629, 000 1 Revision of amounts shown in Project Report dated September 1958, S. Doc. 65, 86th Cong., 1st sess., to include more recent data. The U.S. estimated annual costs would be as follows: 1 Revision of amounts shown in Project Report dated September 1958, S. Doc. 65, 86th Cong., 1st sess., to include more recent data. OPERATION AND MAINTENANCE Pursuant to the terms of the 1944 water treaty, a dam at the Amistad site would be operated and maintained jointly by the Governments of the United States and Mexico through the International Boundary and Water Commission, with each Government retaining full jurisdiction over the portion of the project lying within its own territory. The dam and reservoir would be operated in coordination with the downstream Falcon Reservoir to provide optimum flood control, conservation, and regulation of the waters of the Rio Grande for the two countries, in accordance with the terms of the treaty. The basic principle of operation of the Falcon-Amistad Reservoirs system for storage and regulation of U.S. waters, would be, as it is at present for Falcon Reservoir, that use of waters for domestic and irrigation purposes is paramount, that releases will be made for such purposes as determined and requested by Texas State authorities, and that a sufficient quantity of U.S. waters will be maintained in storage in Falcon Reservoir to immediately supply downstream requirements. Flood control releases would be made from the Amistad Reservoir, when necessary as determined by the Commission, at the minimum practicable rates and, if possible, not in excess of the safe capacity of the channel downstream. If power facilities are provided at a dam at the Amistad site, the release of waters for domestic, irrigation, and flood control purposes would be incidentally utilized for generation of hydroelectric energy. To the extent consistent with these paramount purposes, additional releases would be made by each country, as determined by the respective Section of the Commission, to enable optimum generation of hydroelectric energy, and all such releases would be reregulated in Falcon Reservoir. No U.S. waters required for irrigation would be retained in storage in the Amistad Reservoir solely to maintain a power head. I think this is important and I emphasize it. All boating, fishing, and hunting within a reservoir at the Amistad site would be subject to the regulations and laws of each country within the portion of the reservoir area in its territory. On the U.S. side, it is anticipated that recreational control would be provided by the Texas State Parks Board, and that hunting and fishing would be under the jurisdiction of the Texas Fish and Game Commission. |