Arroyo Hondo (in Santa Clara County, California, United States) is a river that lies east of Milpitas, California. It is located at 37°27?51?N 121°46?32?W? / ?37.46417°N 121.77556°W? / 37.46417; -121.77556. The area is privately owned by the San Francisco Water Department and is closed to public access because of its usage as drinking water. Bound to the east by Oak Ridge and to the west by Poverty Ridge, Arroyo Hondo empties into the Calaveras Reservoir. Its main source is on Mount Hamilton.