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<br />I <br />t <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />3754 <br /> <br />USDA - Soil Conservation Service, Final Report of the Grand <br />Valley Salinity Study <br /> <br />One of the overall objectives of the SCS participation in <br />the Grand Valley Salinity Control Study was to determine the <br />contribution of salt loading from irrigated and related upland <br />areas. The SCS Project Area encompasses the Colorado River Basin <br />from Cameo to the state line, excluding Plateau Creek and the <br />Gunnison River Basin. Salt contribution was reported to be <br />600,000-700,000 tons per year. Apparently, no attempt was made <br />to account for the remaining portion of the Grand Valley salt <br />yield. <br /> <br />USGS - BLM Groundwater Contribution <br /> <br />The USGS and BLM present an estimated salt load contributed <br />by groundwater for the Colorado River mainstem below Glenwood <br />Springs to the state line, excluding the Gunnison River. The <br />average total salt load for this stretch of river between 1966 <br />and 1975 was 1,113,100 tons per year. Measured base flow during <br />the study period was1,040,000 tons per year which indicates that <br />about 93% of the total annual salt load through this stretch was <br />produced by groundwater sources. <br /> <br />BLM 1978-79 Status Report <br /> <br />In their 1978-79 Status Report, the BLM attempted to <br />estimate the amount of the salt load in groundwater attributable <br />to irrigation return flow. Drainage channels in the <br />Grand Valley that were thought to be yielding only irrigation <br />return flow were monitored for flow and quality. The total <br />measured baseflow salt load for the Colorado River between <br />Glenwood Springs and the state line was 1,040,000 tons per year. <br /> <br />-22- <br />