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~ . . OC,2125 12/08/87 Page 1 TO: Todd Nielson Supervisory Soil Conservationist Roosevelt, UT Decelltler 8, 1987 SUBJECT: GEOL - 210-16 Salt Loadill3 Estimate for Fruitland Irrigation Area '!his information is in response to your irGUiry of 12-3-87, as to which sub-basin of the Uinta Basin is CCJlilCIrable to the Fruitland area for purposes of assignill3 a salt loadill3 figure. '!he salt loading figure will be used for PIr566 econanic evaluations of the watershed. '!he sub-basin to be used for salt loadill3 calculations is the Upper D.1chesne River Area; marked 0.56 tons/acre-foot on the map you supplied me. '!his sub-basin is geologically canparable to the Fruitland irrigation area in the followill3 ways - - Both areas have the same geologic source material (the Uinta Formation) for the alluvium that is being irrigated. _ Both areas have the same bedrock unit under the alluvium (the Unita Formation). -. '!he Starvation Reservoir is a man-made phenanena and even though it controls the flow of surface water, the presence of the dam is independent of the soil, soil history, geanorphology and subsurface bedrock. _ It should be noted that the uinta Formation is variable in salt content and sedimentary rock type, '!he surface rocks and the alluvium may not be of canparable salt content. However, the alluvial fan material of Fruitland and the river alluvium of the D.1chesne area are of minimal thickness in the view of deep percolation to the Colorado River. Both areas have the same bedrock for irrigation deep percolation considerations, OJNCLUSICN: Use 0.56 tons/acre-foot as the basis for calculating salt loading in the irrigated area of Fruitland Watershed. /-';'/ -/.-,.,-. /' /y :,. ~(/t "U-//;h.--L.-Ct~ ROBERT C. RASELY r7 Geologist cc: Lee Page, Econanist, SCS, SLC John Marste1l3. Soil Con" SCS, SLC OEe 0 ~ 1SQ7