The upper watershed comprises 90 percent of the total area and supplies a commensurate proportion of the river flow. Stretching from the foothill to alpine regions of the Sierra Nevada, it consists of rugged narrow canyons and ridges with an average local relief of or more from river to rim. Much of the watershed is at high elevation, with 40 percent of the total area above winter snow line. The average precipitation in the upper basin as a whole is . The vast majority of the upper basin is either undeveloped or commercial timber land, with very small areas of agriculture, ranching, and mountain meadows above the tree line. The higher elevations are mostly federal Forest Service land and designated wilderness, while the middle elevations are a patchwork of state, federal and privately owned land. Much of the private timber land has been subject to checker-board clearcutting, which has greatly fragmented wildlife habitat.