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<br />(0 <br />Ul <br />~ <br />~ <br /> <br />In summary, salt contributions from the Upper Basin can be outlined as <br />follows: <br /> <br />Natural Groundwater (diffuse & point sources) <br />Surface Runoff from Rangelands (BLM, private, & State) <br />Surface Runoff from Forests & Error in Calculations <br />Irrigation Returnflow <br />Industrial & Municipal <br /> <br />38% <br />15% <br />5% <br />41% <br />1% <br /> <br />~~l 100% <br /> <br />This exercise gives a gross accounting of sources of salt in the Upper <br />Basin. It was done for the purpose of trying to better identify the <br />contribution of natural sources, an area that has been ignored because <br />of the difficulty in obtaining data. Hyatt et al. (19) states that only <br />20 percent of the 1931 to 1960 average annual salt load from the Upper <br />Basin is traced to its area of origin through actual measurements. <br />Therefore, most estimates of the natural salt load are derived by deter- <br />mining the salt load from agriculture, industry, municipalities, and <br />natural point sources, then attributing the remaining salt to "other <br />natural sources." It is believed that the estimates presented in this <br />report give a more accurate value for the salt load contributed from <br />natural diffuse sources. <br /> <br />15 <br />