Arroyo Hondo is a northwestward-flowing river in Santa Clara County, California, United States, that lies east of Milpitas. The area is privately owned by the San Francisco Water Department and is closed to public access because of its usage as drinking water. Bounded to the east by Oak Ridge and to the west by Poverty Ridge, Arroyo Hondo empties into the Calaveras Reservoir where it joins Calaveras Creek. It is formed by the confluence of Smith Creek and Isabel Creek which drain the west and east slopes of Mount Hamilton, respectively.