WASHINGTON. OKANOGAN PROJECT. GENERAL STATEMENT. The principal data relating to the Okanogan project are summarized below: Summary of principal data relating to Okanogan project. County: Okanogan. Longitude: 119° 40′ W. Township: 34 N., R. 26 E., W. M. Irrigable area: 10,634 acres. Watershed area: 140 square miles. Average rainfall: 8 inches. Range of temperature: Maximum 105°, minimum 10°. Average elevation: 1,000 feet. Principal products: Fruit, hay, nuts, vegetables, and grain. Nearest railroad: Great Northern. Nearest station: Republic (50 miles). Principal market: Local. Kind of headworks: Concrete weir. Reservoir area: 700 acres J500 in Conconully reservoir. 1200 in Salmon Lake reservoir. Capacity of reservoirs: 18,000 acre-feet. Duty of water: 3 acre-feet per acre (diverted). Height of dam: 83 feet. Length of dam: 470 feet. Type of dam: Earth embankment. Length of main canals: 20 miles. Length of laterals: 43 miles. Per cent public land: 10. Character of soil: Volcanic ash, sand, and gravel. Value of irrigated land: $100 to $300 per acre. Date of completion of project: 1907. The Okanogan project (Pl. XCI) will provide water for the irrigation of about 8,650 acres of land in Okanogan County, Wash. The water supply is to be obtained from Salmon River, a stream which drains about 152 square miles in the eastern foothills of the Cascade Mountains. It is estimated that Salmon River will furnish sufficient water for the irrigation of 10,000 acres. The following table gives the recorded flow of Salmon River: The irrigable lands have an elevation of 850 to 1,350 feet above sea, level, and lie in a series of benches sloping toward Okanogan River. The soil is mainly sand, light loam, and volcanic ash. Irrigated lands in alfalfa yield a profit on a valuation of $100 per acre, and lands in fruit or nuts, for which the soil is especially adapted, often yield profits on a much higher valuation. Without irrigation the lands are practically worthless. About 1,425 acres are at present under private irrigation from Salmon River. The water rights of appropriators have been defined by a mutual agreement under which those having a full water right limit their claim to 3 acre-feet per acre for the land they actually irrigate, and those who are at present unable to get water throughout the entire season limit their claim to 3 acre-feet per acre for twothirds of the number of acres at present irrigated. Under this agreement the aggregate vested rights in Salmon Creek are entitled to 4,050 acre-feet during the entire season, leaving sufficient unappropriated water in a dry year for the irrigation of about 8,500 acres. The field operations and other work done during 1903, 1904, and 1905 have been described in the Second, Third, and Fourth Annual Reports of the Reclamation Service. During the summer and fall of 1905 field investigations resulting in the present definite plan for storage works and main canal were carried on, and during the succeeding winter plans and specifications were prepared. The lands under the project have been classified and a general scheme of distribution system has been outlined. Office buildings, project engineer's cottage, assistants' dormitory, mess house, and barn have been built and water supply and sewerage systems have been installed. RESERVOIRS. To utilize the entire flow of Salmon River in years of low run-off a total storage capacity of 13,000 acre-feet is necessary. As it is considered desirable to hold over from a low to a high year as much water as practicable the storage works, Salmon Lake reservoir and Conconully reservoir (Pl. XCII), have been planned for a total capacity of 18,000 acre-feet. With this capacity it is believed that the minimum amount of water available for any one year will be 36,000 acre-feet except in case of two successive low years. Salmon Lake reservoir, a natural lake about 31 miles long, immediately east of the town of Conconully, is on a small branch of the North Fork of Salmon River. It has an available capacity of 2,000 acre-feet, the low-water elevation being 2,285 feet and high water 2,295 feet above sea level. It will be necessary to excavate an inlet canal about 1,500 feet long and to build a small concrete outlet structure, with provision for flashboard control. Conconully reservoir, immediately south of the town of Conconully, will be created by building an earthen dam across Salmon River below the junction of the North and West forks. The capacity of the reservoir will be 16,000 acre-feet. The dam will have a maximum height of 83 feet and a length of 470 feet. High-water elevation is 2,287 feet above sea level, and maximum draft is 57 feet. The outlet will be through a reenforced concrete conduit of 4 feet inside diameter, which is controlled by a 36-inch cast-iron gate. On June 27, 1906, only one bid was received for building the necessary storage works. The total bid was $164,153.75, and as this was deemed excessive it was rejected. Bid opened June 27, 1906, for storage works, Okanogan project. Clearing and grubbing Conconully dam site.. .do.. 6 150.00 900.00 Stripping dam site spillway, waste channel, and burrow pits..cu. yards.. Excavation of cut-off trenches: CANALS AND DISTRIBUTION SYSTEM. The supply from the Salmon and Conconully reservoirs will follow the natural channel of Salmon River for about 12 miles to the point of diversion at an elevation of 1,371 feet. The lands to be irrigated are reached about a mile below the point of diversion. There will be about 20 miles of main canal varying in capacity from 100 to 30 second-feet, and about 40 miles of canal with a capacity of less than 30 second-feet. Bids for the main canal were to have been opened on June 27, 1906, but on that date only one bid was received. As this bid was deemed excessive it was rejected. Bid opened June 27, 1906, for main canal and appurtenant structures, Okanogan project. [Specifications No. 89.] |