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markedly different habitats abruptly, from a sand-bed alluvial river to canyon confined bedrock river. Vegetation and Precipitation A variety of vegetative communities occur in the basin including: desert shrub, sagebrush grasslands, aspen woodland, montane forests, some wetland areas, riparian communities along the river and tributaries, and some subalpine vegetation along the far eastern border. Much of the erosive topography is covered with the sparse vegetation of the desert shrubs and sagebrush grasslands. This vegetation occurs on gentle to moderate slopes and is characterized by sagebrush, rabbitbrush, serviceberry, and snowberry and various grasses including wheatgrasses, bluegrasses, prairie junegrass, Indian ricegrass, needle grass, cheatgrass and fescue. The distribution of vegetation in the Little Snake basin can be explained by the combination of soil conditions, topography and precipitation. Langbein and Schumm (1958) developed a relationship between mean annual sediment yield and mean annual precipitation. It showed that in areas where the mean annual precipitation was greater than 35 cm per year, the vegetative cover is more dense and more diverse. Soil erosion decreases for areas of higher precipitation because the vegetation protects the soil from raindrop impact and the soil particles are bound together with root systems. For areas with a mean annual precipitation of less than 25 cm, sediment yield is limited by the low rainfall/runoff. A mean annual rainfall of 23 to 30 cm occurs in the lower elevations of the Little Snake watershed (Andrews 1978). This rainfall supports desert shrub and lower grassland vegetation community. The combination of limited rainfall, sparse vegetation and erosive geology in the lower Little Snake basin generates a high sediment yield in the tributary system. 11