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16 the Colorado River, For instance, the central to lower reach of the w ~ Dirty Devil-River, from Hanksville to Lake Powell, carries low l'V ~. quality water, but the exact delineation of the areas contributing most of the dissolved constitutents is not specified. This generality in assigning a given salinity to a long channel reach and its immedi- ate tributaries may be misleading to government officials whose duty it is to plan the reduction of salt yields from diffuse source areas. It is also very general because the water quality data upon which this and other similar maps (e.g., Iorns, Hembree and Oakland, 1965) are based is very meager, Most of it is derived from samples taken from main stems or main tributary basins (from which little can be con- cluded about the source areas) or from mountainous watersheds yield- ing very high quality runoff. Note, for example, that there are only four locations in the Utah section of the Upper Basin (Fig, 1,8) where both chemical quality and sediment discharges are recorded, and all are on large rivers; in addition, there are only nine sections, all in rivers draining more than 100 square miles, for which water quality data is available (for some, this includes merely two analyzed water samples per year). Also, note that all sites where data were obtained on the specific conductance of surface water (Fig. 1-8) are for large rivers or small mountain streams, Although the identification of major source areas of salts is not sufficient to delineate potential salinity hazard areas, it is interesting to note that the watersheds within the Upper Basin with high sediment yields occupy the terrain of the major source areas of salts. This areal correspondence may point to a causal relationship between sediment transport and solute pickup.