The San Juan River drains approximately in Colorado, New Mexico, Utah and Arizona; the watershed land area is almost the same size as the state of West Virginia. The main stem of the river does not actually flow through Arizona, but comes very close at the Four Corners. The highest point in the San Juan River watershed is Windom Peak, located near the headwaters of the Animas River. The lowest elevation, where the San Juan River flows into Lake Powell, has a normal maximum elevation of but typically fluctuates dozens of feet per year due to seasonal nature of runoff in the Colorado River Basin affecting the reservoir level. Most of the watershed is rural, with some extremely remote, uninhabited areas. About 75 percent of the watershed is shrubland, rangeland and grassland. Due to the low rainfall and lack of substantial groundwater reserves, agricultural use is scarce, except for river valleys and in higher foothill areas influenced by wetter montane climates. About 2.3 percent of the watershed is dryland farms, and 1.6 percent is irrigated. Forests cover about 20 percent of the watershed, mostly at high elevations.