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<br />Q <br />N <br />~ <br />1-". <br /> <br />, <br /> <br />2 <br /> <br />week period and a report was issued that included targeting <br />(identification) of areas within the watershed that were undergoing <br />accelerated erosion and would respond to land treatment pla~ning to' <br />lower rates of sediment and salt yield to the Colorado River. <br />Quantities and rates of sediment and salt that could be controlled <br />by implementation of land treatment measures. were. developed. by' <br />geomorphic unit. The reports were delivered to BLM and scs.field <br />office managers for use in planning and environmental. studies. <br /> <br />The pacific Southwest Inter-Agency committee (PSIAC), 1968, <br />Sediment Yield Procedure was used to model sediment yield rates for <br />various geomorphic units. PSIAC is a resource evaluati.on tcl;lol.that <br />can be used to target severely eroding and high salt.yiel!iing areas <br />within hydrologic units. This sediment yield model isadoQumente!i <br />reliable procedure that may be applied to individual geomorffihic <br />units in conjunction with a sediment delivery ratio to predict <br />sediment yield and salt yield. <br /> <br /> <br />INTRODUCTION <br /> <br />salinity control work in the Colorado River Basin has been . <br />accomplished during the last decade by achieving greater irrigation <br />efficiency on irrigate!icropland. Rangeland watershed salinity <br />control was deemed too expensive for the very large .numberof acres <br />of rangeland within the river basin. The Soil Conservation service ! <br />(SCS, 1986) Sand Wash Watershed Rangeland sediment and Salinity <br />Control Project is an example of cost effective rangeland salinity <br />control at approximately $36.00 per ton. <br /> <br />Salinity control planning and problem area identification on . <br />rangeland can be accomplished by modelling rangeland waters~ed~ <br />using a geomorphic-hydrologic unit model baseincol:1juncti,OPwlth . <br />resoUrce targeting procedures. These types o.f studies' have>shoWJ1 <br />that a typical rangeland watershed will haveapproximately7,%,.to . <br />15% of the area in severely eroding condition. These severely. " <br />eroding areas yield salts from soil and rock fragments carried as <br />sediment in storm runoff and are responsible for.approximatt!lly.75% <br />to 90% of the accelerated or excessive sediment load being yielded <br />to the colorado River due to present or historic management., . <br />practices. The Pacific Souhtwest Interagency Committee(PS~AC) . <br />1968 sediment Yield Procedure was used to document and quantify the <br />sediment and salt related yields from the severely ero!iing areas. <br />The salt yield was estimated as a percentage of. the total sediment <br />yield. <br /> <br />The Colorado River Basin Rangeland Salinity Control Project was <br />proposed by the SCS in a water quality issue paper (Rasely and <br />Petersen, 1988) and implemented as a pilot study to test the <br />resource modelling procedures and cost effectiveness of controlling <br />salinity on rangeland watersheds (USDA, SCS, 1989). The project <br />was organized with a primary interdisciplinary rangeland evaluation <br />team consisting of a geologist-team leader (SCS), range <br />conservationist (Bureau of Land Management-BLM) and a hydrologist <br /> <br /> <br />i~ <br />i <br />"~ <br />,i <br /> <br />\< <br />:~ <br /> <br />.! <br />,~ <br />,] <br /> <br />) <br /> <br />