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CHAPTER I PURPOSE AND NEED placed in pipe, and up to about 17,000 acres of fields may be leveled with full implementation (SCS 1977). Plans aimed at reducing erosion and salt contribution are being pro- posed to private owners of dry grazing land north of the Government High- line Canal. The on-farm salinity control program also includes a volun- tary program whereby participating farmers agree to improve wildlife habitat on their land through various farming practices. This improve- ment would then serve as replacement for habitat losses. Reclamation has agreed to provide additional wildlife habitat to compensate for losses due to the on-farm program in the event the voluntary program does not accomplish its goals. The amount of additional habitat would not be determined until the Soil Conservation Service Wildlife Habitat Monitoring and Evaluation Study is completed in about 1989. The SCS is also lining some off-farm laterals, incorporating sizing criteria established by and mutually agreed upon by SCS and Reclamation. Highest priority is being given to laterals that affect on-farm improve- ment measures. Effects of on-farm improvements on water quality and wildlife habitat are also being monitored by the SCS. The SCS estimates that the on-farm improvements could result in a total salt loading reduc- tion of about 130,000 tons annually. In close relation to the Soil Conservation Service and the Bureau of Reclamation studies, the Agricultural Research Service, the Bureau of • Land Management (BLM), Colorado State University, the Colorado State Extension Service, and the Colorado Water Conservation Board are con- ducting or have conducted research and demonstration programs in the valley. Colorado River Basin Salinit In the Colorado River Basin, salt pickup from the Grand Valley Unit and other sources has resulted in the water quality of the Colorado River deteriorating over the long term since riverflows have been developed for beneficial use. At its headwaters in the mountains of north-central Colorado, the Colorado River has a salinity concentration of 50 milligrams per liter (mg/L). The concentration progressively increases downstream as a result of water diversions and salt contributions from a variety of sources. In 1983, the average total dissolved solids (TDS) concentration was about 710 mg/L at Imperial Dam. In 20 of the last 23 years, average annual TDS exceeded 800 mg/L, with a maximum of 896 mg/L in 1970. Unless con- trol measures are undertaken, the concentrations are expected to increase as the Colorado River Basin States continue to develop their compact- apportioned waters.l/ 1/ The waters of the Colorado River are divided by the Colorado River Compact of 1922, agreed on by the seven Colorado River Basin States (Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming). 8