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Causes and Impacts of Salinity Erosion Several researchers[8-11] have shown that erosion of saline shales and dissolution of efflorescence (surface salts) increase salinity during thunderstorms. Low elevation snowmelt on saline geologic formations may also contribute significantly to salinity. Analyses of the Green River near the Green River, Utah, Station indicate that salinity remains unusually high during peak flows associated with snowmelt runoff events. Reclamation studies on the McElmo Creek Salinity Control Unit found that approximately 32 per- cent of the total salt load could be related to runoff events. Other studies by Reclamation show that 21 percent of the Price River salt load and 14 percent of the San Rafael River salt load are related to natural runoff events. Studies[12] conducted on Mancos Shale in the Upper Colorado River Basin have demonstrated a positive relationship between sediment yield and salt production. Sediment yield increases as a result of either upland erosion or streambank. and gully erosion. Upland erosion is attributed to rill and inter-rill flow. Salt and sediment yields are dependent upon storm period, landform type, and the soluble mineral content of the geologic formation. Studies[13] conducted in the Price River Basin have demonstrated that the highest salt and sediment concentrations occur in the first streamflow event following a long period of no discharge. The accumulation of salts in the channel is attributed to efflorescence resulting from the drying of the channel. Salt yields occurring after the initial flushing of the channel are similar to those found in the surrounding watershed soils. Sediment and the resulting salt yield are highly dependent upon landform type. Three major landform types-badlands, pediments, and alluvial valleys-are associated with the Mancos Shale terrain. Badlands are the most erosionally unstable, with sediment yields as high as 15 tons per acre[14]. Rilling accounts for approximately 80 percent of the erosion[13]. Because salt production is closely related to sediment yield and the badland soils have not been leached of their soluble minerals, they produce the greatest amount of salt of the landform types. Pediments are gently inclined planate erosion surfaces carved in bedrock and generally veneered with fluvial gravels. The surface slopes of pediments are gentle, making them relatively stable. Pediments have deeper soils and higher infiltration rates than badlands; thus, they support a greater vegetation cover and are less erosive. Alluvial valleys are formed by a change in gradient and the deposition of sediment. They are stable except along the channel where headcutting and gullying occur. Most of the salts have been leached from the alluvial deposits; thus, erosion of their landform type yields less salts per unit volume of sediment than the other two landform types. However, channels incised into alluvium incorporate both sediment and salt from sloughed channel banks and salts from efflorescence at the alluvium-bedrock contacts[ 12]. 13