37°41′1.75″N 121°46′15.92″W / 37.6838194°N 121.7710889°W
The Mocho Subbasin is the largest of the groundwater subbasins in the watershed of the Livermore Valley in Northern California. This subbasin is bounded to the west by the Livermore Fault Zone and to the east by the Tesla Fault. Some groundwater flow occurs across these fault boundaries, but flows are discontinuous below a depth of fifty feet across the Tesla Fault and south of the Arroyo Mocho channel across the Livermore Fault.[1] Surface watercourses in this unit include Arroyo Valle and Arroyo Seco.