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36 The average reduction in deep percolation returning to the river with the USDA program is 6 inches. The average reduction in salt ~) loading of returnflow is 1,30 tons per acre foot. This en translates into an average salt load reduction of ,65 tons per ~ irrigated acre treated, The USDA program will reduce onfarm salt QQ loading about 50 percent, Several aspects of the salt and water budgets for the Uintah are different than the Colorado units. The first and most significant attribute is the short water supply, This makes defining an average year more difficult, During wet years excess water is applied and there is a lot of deep percolation, and in drought years there still may be excess water added in the spring, but irrigators run out of water in the summer, When new and improved systems are installed the first increment of conserved water may go to reduce water shortages, However, irrigators may still run out of water in the summer. The second attribute in the uintah Basin is the large acreage of wetlands and phreatophetic vegetation, which uses deep percolating and seepage water. This reduces the water returning to the river and salt pickup. Over half of the deep percolating water is used by wetland vegetation, and their is some reuse for irrigation, with improvements in the delivery system and onfarm systems less water will be used by wetland vegetation and will add to instream flow for fisheries, ANALYSIS of USGS WATER QUALITY DATA A trend analysis was used to identify a decrease in the salt load of the Duchesne River before it enters the Green River due to the USDA salinity control program. Water quality data was obtained from analysis of water samples collected on the Duchesne River near Randlett monitoring station by the U.S.Geological survey. Trend analysis is a statistical procedure used to detect changes in stream water quality at a monitoring station over time. SCS used a linear regression analysis, The regression shows a decrease in the salt load since the USDA program started in 1981. A regression analysis was performed on the 1941-1980 pre-project years and the 1981 to 1992 project years, Figure 1 displays the results. The slopes of these regressions are different, which points to an effect on the salt loading of the Duchesne River. USGS publishe~a f~ep~rt intitled "National Water Summary 1990-91- -Stream wateriQuality: Utah", USGS Water Supply Paper 2400, The results of there independent study confirms the conclusions of the SCS water quality trend analysis, Water quality data were analyzed for trends by using the seasonal Kendall test, A downward trend in sulfate concentration, chloride concentration, and dissolved solids at site 8 on the Duchesne River in the Upper Colorado River Basin has been identified in the paper as probably the result of improvements in irrigation water management.