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SUMMARY (Continued) Summa ry Ta ble 1 Numeric criteria for the lower Colorado River Station Below Hoover Dam Below Parker Dam !!c.~erial Dam Annual flow-weighted concentration (mg!L)___ 723 747 879 The goal of the salinity control program is to maintain concentra- tions at or below these criteria. Salinity control measures of the Soil Conservation Service (SCS) and the Bureau of Reclamation (Reclamation) to date are removing 140,800 tons of salt annually from the Colorado River system. Over a million tons of salt per year will need to be re- moved by the year 2010 to maintain average salinity below the numeric criteria level of 879 mg!L at Imperial Dam. In the McElmo Creek area, salt loading primarily results from con- veyance seepage in the MVIC system and from irrigation deep percolation into the ground water system. This seepage water dissolves salts from the soil and the underlying Mancos Shale and then surfaces in McElmo Creek. Return flows to McElmo Creek, including surface and ground water, have an estimated combined salinity level of approximately 1,990 mg!L, while the estimated concentration of the ground water alone is approximately 3,900 mg!L. With the Dolores Project in operation, the total salt pickup f rom the a rea would be approxima tely 144,200 tons annually. The objective of the proposed salinity control features is to decrease the amount of salt leaving the study area and entering the Colorado River system. As noted above, the Towaoc Canal would be realigned from the west to the east of the City of Cortez. In the 1977 FES, the Towaoc Canal would convey full service irrigation water to the Towaoc area along the western alignment independent of all MVIC facilities. In recent years, however, a reevaluation of the Towaoc Canal alignment has identified several factors, in addition to achieving salinity control benefits, that favor a rerouting of the canal to the east of Cortez. These factors are significant economic savings in right-of-way and land acquisition costs as well as significant public support because it would prevent the disturbance and loss of agricultural land by using the existing Lower Hermana Lateral and HighUne Ditch alignments. Additionally, using the east alignment and combining the canals would decrease the salt loading effect of the Towaoc Canal by an estimated 7,500 tons per year. The Dolores Project interrelates with other Federal projects cur- rently under investigation or construction by the U.S. Department of Agriculture. These projects include the proposed on-farm improvement 5-3