AZ vs. CA:24 California Exhibits, Vol. XXIV; Miscellaneous

page 156

156 PROBLEMS OF IMPERIAL VALLEY AND VICINITY. DOLORES PROJECT. Irrigable area, 80,000 acres or more. Mean annual temperature, 45°. Mean annual precipitation, 14 inches. Precipitation during growing season, 7 inches. Elevation, 6,000 to 6,500 feet. Interval between killing frosts, 125 days. Transportation, Denver & Rio Grande Railroad, narrow gage; nearest station, Dolores, 20 to 60 miles. -*Irrigation 'plan.-The Dolores reservoir is to be built on Dolores River just below mouth of Beaver Creek, about 10 miles downstream from town of Dolores. Present water level is to be raised 230 feet and diversion to be made 173 feet above stream bed, leaving 120,000 acre-feet of active storage. The canal will follow the south side of the canyon for 14 miles and pass with a 4,800-foot tunnel to the headwaters of Montezuma Creek in the San Juan Basin. From this point the main canal branches to the south and northwest. The lands to be irrigated consist of mesas sloping toward the San Juan River and separated by deeply cut drainage channels. The canal from the reservoir to the point where the irrigable lands are reached will be built through a very difficult country, with a large amount of flume and tunnel work. After passing the San Juan divide, the canal system will not be difficult of construction. Duty of water.-Irrigation diversions of 2 acre-feet per acre will probably prove sufficient, as much of the area has recently been successfully dry-farmed. Water supply.-All water will be derived from the Dolores River. The average recorded discharge at Dolores is 291,000 acre-feet annually, which when adjusted for normal years by comparison with Animas River at Durango would be increased to 319,000 acre-feet. Inflow from Beaver Creek and other drainage to the dam site would add 20,000 acre-feet. On the basis of an average year, the relation of water supply and demand for an 80,000-acre development would be as follows: Water supply and irrigation requirements. [Acre-feet.] Month. Discharge of Dolores at reservoir. Prior rights of Montezuma project. Balance for Dolores project. Demand for Dolores project. Draft on storage. April...................................... May....................................... June....................................... July....................................... August.................................... September................................. October-March............................ Total................................ 48,000 104,000 91,000 29,000 13,000 8,000 46,000 8,000 20,000 30,000 20,000 15,000 7,000 40,000 84,000 61,000 9,000 1,000 46,000 13,000 32,000 48,000 32,000 24,000 11,000 339,000 100,000 241,000 160,000 23,000 24,000 10,000 57,000 With 120,000 acre-feet of storage available there is sufficient holdover capacity to tide the project over short years, excepting only where these occur in a series.