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30 The drain baseflow (Return from irrigation, Hydro-Salinity App. p.52 & 53. In the 1989 EIS Suppl. 4.1 tns/ac ft is used) is: preproj F w/o F with 18,000 ac ft 21,000 ac ft 17,000 ac ft 97,000 tons salt 120,000 tons salt 97,000 tons salt 5.2 tns/ac ft 5.7 tns/ac ft 5.6 tns/ac ft 3820 mg/l 4180 mg/l 4110 mg/l Salt Budget (USBR, App.B, p.53) for McElmo Creek: Drain Return Surface Return Return from Irrig. Canal Onfarm Pre 97,000 3,000 Tons of salt 100,000 33,000 67,000 F/WO F/W 120,000 4,000 124,000 42,000 82,000 97,000 10,000 107,000 20,000 87,000 USBR budgets for the onfarm portion: The future with project results in an increase of 20,000 tons per year in onfarm salt loading from the pre-project condition. There would be little chance for reducing the 87,000 tons of onfarm salt loading, as the USBR budget is based on 7 % ditch seepage and a 67 % onfarm application efficiency. SCS assumed a 45% present irrigation application efficiency and 70% with project. The onfarm program requires the USBR delivery system improvements to help facilitate gravity pressurized sprinkler systems on certain laterals. The USBR Dolores Project - 1989 EIS Supplement pp. 31,34,41,42 Project Salt Loading Canal lining/pipe Net Salt loading +43,150 tons/year -24,500 tons/year +18,650 tons/year USBR Canal Lining/Pipe 41. 3 miles 24,500 tons/ 41.3 miles = 593 tons per mile Seepage Reduction is 6,000 acre feet or 145 ac ft per mi This translates into 4.1 tons of salt loading / acre foot.