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<br />" <br /> <br />N <br />ClC <br />C,Q <br />1'.1\ <br /> <br />11 <br /> <br />acre-feet per square mile (approximately 3.3 ton per acre) with a <br />sediment yield. classification of 4 - High. Laboratory tests on <br />sal t content of sediment are 10%, 8..5% and 9%. It is determined <br />that 9% is a representative figu~e. The annual salt yield from the <br />geomorphic unit is, 9% of 3..3 t.ons per acre or approximately 0.3 <br />tons per acre. The geomorphic unit has a channel outlet to an <br />intermittent channel with 3.2 miles of canyon-type channel delivery <br />to the Green River. There are minor occurrences of sand bars and <br />flood plain deposits along the channels within the geomorphic unit. <br />It is estimated that approximately 90% of the sediment from the <br />geomorphic unit actually ,are transported to the Green River. This <br />percentage is known as the sediment delivery ratio, (BOR). Inthis <br />example it will be assumed that the trapped'sediment contains its <br />percentage of slat. It some cases the: sediment deposited in bars <br />and flood plains will have already yielded its salt to solution <br />through mechanical and chemical erosion ,and therefore, the SOR will <br />not apply to the salt value (then the salt percent should be <br />applied to the sediment tonnage before the BDR is applied). <br /> <br />The Present Condition annual salt yield to the COlorado River is <br />estimated by the following. calculation: <br />0.3 ton/acre x 1760 acres x .9 (BOR) = 475 tons of salt (Present). <br /> <br />The above example was fOr the Present condition. Thel"uture <br />without Project condition is determined to be a continuation 'of the <br />Present conditions with a slight increase in the Upland Erosion <br />factor by 2 points and a 2 point increase in the Channel Erosion <br />factor. Thereby giving a total rating of 76 points for an annual <br />sediment yield of 1. 275 acre-feet per square mile (approximately <br />3.8 tons per acre). The FWOP annual estimated salt yield 'is <br />calculated as follows: <br />3.8 ton/acre x .09 salt % x 1760 acres x .9 BOR = 542 tons of salt <br />(FWOP). <br /> <br />The next rating is for the Future With Project condition. It is <br />determined in the field that this geomorphic unit would respond to <br />a change in management and land treatment planning. ,The proposed <br />changes are some livestock exclusion of major channel areas, <br />fencing, chaining or harrowing of strips of sagebrush to disturb <br />the potential for rapid collection of overland flows and to disrupt <br />concentrated flow paths. Gully areas up to 2 feet deep will be <br />filled with litter and sediment. An appropriate vegetative mix is <br />proposed for the reseeding. Cattle will be limited to a late <br />spring-early summer use. The following is the FWP rating for the <br />geomorphic unit: <br /> <br />Factors <br /> <br />sediment Yield Characteristics <br /> <br />Rating <br /> <br />a Geology <br />b Soils <br /> <br />Lacustrine shales, Jur-Morrison <br />Hi shrink-swell, dispersive, <br />hi CaC03, minor rock frags <br />Infreq convective storms, freeze- <br /> <br />5 <br /> <br />8 <br /> <br />c Climate <br />