Watershed
The stream drains much of the southern portion of the city of Livermore, and it also flows through and drains a considerable fraction of the city of Pleasanton. Water quality measurements in this stream indicate a pH level of 7.0, or neutral with respect to acidity; phosphate levels were not detectable.
In the middle reaches of Arroyo del Valle south of Livermore, there has been considerable historic grazing use. Depth to groundwater in this reach of the watershed typically ranges from 50 feet (15 m) to 100 feet (30 m) and flows to the west. Subsequent to this reach, the Arroyo del Valle flows down the moderately sloping hills to enter gravel pits, where extraction (but not processing) has historically been conducted by Lone Star Industries.
Del Valle Dam forms the reservoir Lake Del Valle in southeastern Alameda County.
The upper reaches of Arroyo del Valle stretch into northeastern Santa Clara County where the mainstem if formed by the confluence of San Antonio Creek and Arroyo Bayo. San Antonio Creek's origin is on the western slope of 3,804 feet (1,159 m) Mount Stakes, west of the Santa Clara-Stanislaus County border, about 32 miles (51 km) southeast of Livermore. San Antonio Creek traverses the San Antonio Valley as it heads west to Arroyo del Valle. Arroyo Bayo also has its origin on Mount Stakes southwestern slope and traverses Upper San Antonio Valley as it also heads west to Arroyo del Valle.
Read more about this topic: Arroyo Del Valle