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~ m 00 CO The adjusted dissolved-solids concentration in the Colorado River below Glenwood Springs (site 52) was 807 mg/L. The estimated base-flow salt load in the Colorado River below G1enwood Springs was 974,000 ton/yr (fig. 8), and the' base-flow discharge was 1,226 ft3/s. This estimate included adjustments ,for Williams Fork, Dillon, Green Mountain, and Ruedi Reservoirs. The total calculated contributions from the Colorado River upper headwaters subbasin was 645,000 ton/yr, and the adjusted discharge addition was 470 ft3/s. In the reach between Dotsero and Glenwood Springs, the salt load of the Colorado River increased by 719,000 ton/yr. The Roaring Fork River added 183,000 ton/yr, and other measured tributary inflow to the Colorado River in this reach added 1,500 ton/yr. The remaining 534,000 ton/yr in this reach probably 'originates from many hot and warm springs. If these springs are the primary source of the additional salt, they contribute about one-half of the annual base-flow salt load for the Upper Colorado River Basin ,above G1enwood Springs. Under this assumption the combined discharge of the Dotsero-Glenwood Springs hot springs group was estimated using equation 3 outlined in the "Data Collection and Method of Analysis" section of this report. An estimated discharge of 18 ft3/s was computed for this group of springs. Salt-load distribution The areal distribution of the sources of flow and estimated salt load in the Colorado upper headwaters subregion indicates that the Blue River produces an estimated 1 percent of the base-flow salt load and 15 percent of the base-flow discharge; the Eagle River produces an estimated 14 percent of the base-flow salt load and about 16 percent of the base-flow discharge; the Roaring Fork River produces an estimated 19 percent of the base-flow salt load and about 30 percent of the base-flow discharge; and the Dotsero-Glenwood Springs hot springs produce about 55 percent of the estimated base-flow salt load and an insignificant volume of flow. Combined, these sources represent 89 percent of the estimated base-flow salt load and 61,percent of the base- flow discharge of the Colorado upper headwaters subregion. The graph of salt load, dissolved-solids concentration, and discharge for the main stem of the Colorado River (fig. 9) depicts the impact of these various sources on salinity levels of the Colorado River. A slight increase in salt load and dissolved-solids concentration in the main stem of the Colorado River is apparent until its confluence with the Eagle River. The most apparent impact is the large increase in salt load and dissolved-solids concentration of the Colorado River downstream from the Eagle River near Glenwood Springs due to the discharge of highly saline mineral springs along this reach. The base-flow salt loads measured at selected sites in the Colorado upper headwaters subregion were compared with the total annual salt load reported by BLM (Bentley and others, 1978). The estimated base-flow salt load of 30