WSP04560 - Laserfiche WebLink

Home Browse Search

29 .. USBR 1989 Dolores Project Final Supplement to Final EIS and ~ Appendix B on Water Supply /Hydrosalinity. ~ ~ Summary and extracts from the published USBR EIS and appendicies. ~y With the completion of the Dolores Project by USBR the salt load in the outflow of McElmo Creek would increase to 174,000 tons (p.53) of salt annually. with USBR salinity control features the proposed plan shows outflow of 82,000 acre feet with a salt load of 147,000 tons. This is a concentration of 1300 mg/l, which compares to the present average concentration of 2600 mg/l. The flow diagram shows about 34,000 acre feet of good quality (156 mg/l) inflow being spilled into the outflow of McElmo Creek, thereby diluting the concentration of outflow in half. Canal inflow into Montezuma Valley would increase from about 105,000 acre feet to 139,000 acre feet per year. With a concentration of 156 mg/l or .2 tons per acre foot, canal inflow to the Montezuma Valley carries 30,000 tons of salt. The total salt pickup from the area without salinity control would be 144,000 tons/year. The salt load pickup from the irrigated area with the USBR Dolores Project to deliver additional water, but including a salinity control plan would be 118,000 tons. Salt loading comes from both irrigation and diffuse sources, with irrigation being the main contributor. The local contribution from precipitation is estimated to be 13,000 acre feet and 39,500 tons per year (USBR 1988. Appendix B Water Supply/Hyrosalinity p.56). Natural runoff and salt loading is not expected to change with project activities. The irrigation budget displayed on page 52 & 53 assumes 73 % onfarm application efficiency for preproject and future without project and a 67 % efficiency for future with salinity control. These values need some explanation and a reference. The following data was abstracted from USBR Appendix B dated January, 1988. pp. 52,53,56,58. Canal Ditch T. W. Deep Subtot Phreat. Return Seep. Seep. Seep percol. Use Thousand acre feet Pre 10 6 6 8 30 -12 18 F/WO 12 7 6 9 34 -13 ?1 F/W 6 7 6 9 28 -11 17 Note: About 40 percent of the seepage and deep percolation is consumed by phreatophytes or wetland habitat. SCS inventory would place the value closer to 20 percent (4000 acres at 1.5 AF/A would be 6,000 acre feet.)