The Spring Mountains divide the Pahrump Valley and Amargosa River basins from the Las Vegas Valley watershed, which drains into the Colorado River watershed, by way of Las Vegas Wash into Lake Mead, thus the mountains define part of the boundary of the Great Basin. The Great Basin Divide, (one of the Great Basin region borders) continues north through the Indian Springs Pass region, then turns due east at the perimeter mountain ranges north of Las Vegas.