Arroyo Seco (Alameda County)

Arroyo Seco is an 11.7-mile-long (18.8 km)[2] watercourse in Alameda County, California, that traverses through the city of Livermore. Arroyo Seco means "dry stream" in Spanish. Arroyo Seco lies above the Arroyo Seco watershed, which includes the eastern part of the city of Livermore and also the Sandia National Laboratory. The Mocho Subbasin is the largest of the subbasins in the Livermore Valley watershed. 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 50 feet (15 m) across the Tesla Fault and south of the Arroyo Mocho channel across the Livermore Fault.[3] A number of threatened and endangered species occur in this watershed.[4]

Arroyo Seco
Location of the mouth in California
Location
Country	United States
State	California
Region	Alameda County
City	Livermore
Physical characteristics
Source	spring
• location	8 mi (10 km) southeast of Livermore
• coordinates	37°39′57″N 121°36′51″W[1]
• elevation	1,990 ft (610 m)
Mouth	Arroyo Las Positas
• location	north of Livermore
• coordinates	37°42′20″N 121°45′23″W[1]
• elevation	482 ft (147 m)[1]