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~ co ~ ~ salinity of the diversion averages 130 mg/L. while McElmo Creek salinity is about 2,600 mgJL at the Colorado-Utah State line. Data collected during the study included the following: (1) 15 ponding tests were run on Montezuma Valley Irrigation Company canal sections, and 115 miles of canals within the Basin were characterized according to soil structure; (2) ground water research in the Basin consisted of 125 wells monitored for water table elevation. salinity, and hydraulic conductivity; (3) computer models were used to determine what proportion irrigation, canal seepage, and precipitation contribute to total salt load (subbasin by subbasin); and, (4) irrigation research was done on 7 test farms in the Basin representing various soil types. farm sizes, irrigation methods, and farm management. Results indicate seepage rates for most of the Montezuma Valley Irrigation Company distribution system are low to moderate except for locations where canal sections have been cut through shale and sandstone and seepage rates are high. Only when results from the four subbasins were combined into a total Basin water budget could surface water, ground water, precipitation, and salts associated with water movement be determined, but the use of the Basin water budget is limited because of the apparent inaccuracies of data used to calculate the budget. Through a Multiple Objective Planning Process and Public Involvement Program, several alternatives were proposed to reduce salinity. The Reclamation recommended plan is to line three sections of Montezuma Valley Irrigation Company canals--two on the Lone pine Lateral and one on the Upper Hermana Lateral--and to install laterals from the proposed Towaoc-Highline Canal (a Dolores project feature) to serve the Rocky Ford Ditch Service area. The Rocky Ford Ditch would then be abandoned as part of the plan, and its flows would be combined into the proposed Towaoc-Highline Canal. The plan will reduce ground water seepage from canals by 4,060 acre-feet a year and reduce the amount of salt returned to McElmo Creek. The McElmo Creek Unit was authorized as part of the OOlores project, a participating project of the Colorado River Storage Project. Included are seepage control from the Towaoc-Highline Combined Canal, Rocky Ford laterals, Lone pine Lateral, and the Upper Hermana Lateral. The McElmo Creek USDA salinity control report was published in 1983. The recommended implementation plans call for treatment of about 19,700 acres with sprinkler irrigation systems (10,400 acres gravity and 9,300 acres pumped) and about 270 miles of onfarm ditch and lateral lining. By combining the Dolores Project and the McElmo Creek salinity project, the more efficient gravity pressure sprinkler systems can be installed to an additional 9,000 acres over the original USDA implementation plan. The DOl and USDA projects are fully compatible; however, a fully coordinated effort has been initiated so the design and implementation of DOl delivery and distribution systems complement the design and installation of onfarro systems. A reevaluation of the USDA implementation schedule is underway to allow for coordinated on-farm and off-farm planning. VII-22 -