Arroyo Seco is an 11.7 miles (18.8 km) watercourse

Watercourse

A watercourse is any flowing body of water. These include rivers, streams, anabranches, and so forth.-See also:* physical geography* Environmental flow* Waterway* Hydrology* Wadi-External links:...

 in Alameda County, California

Alameda County, California

Alameda County is a county in the U.S. state of California. It occupies most of the East Bay region of the San Francisco Bay Area. As of the 2010 census it had a population of 1,510,271, making it the 7th most populous county in the state...

, that traverses through the city of Livermore

Livermore, California

Livermore is a city in Alameda County. The population as of 2010 was 80,968. Livermore is located on the eastern edge of California's San Francisco Bay Area....

. Arroyo Seco means "dry stream" in Spanish

Spanish language

Spanish , also known as Castilian , is a Romance language in the Ibero-Romance group that evolved from several languages and dialects in central-northern Iberia around the 9th century and gradually spread with the expansion of the Kingdom of Castile into central and southern Iberia during the...

. Arroyo Seco lies above the Arroyo Seco watershed, which includes the eastern part of the city of Livermore and also the Lawrence Livermore National Laboratory

Lawrence Livermore National Laboratory

The Lawrence Livermore National Laboratory , just outside Livermore, California, is a Federally Funded Research and Development Center founded by the University of California in 1952...

. The Mocho Subbasin is the largest of the subbasins in the Livermore Valley

Livermore Valley

The Livermore Valley AVA is an American Viticultural Area in Alameda County, California, surrounding the city of Livermore in the Tri-Valley region. Both the AVA and the city are named after Robert Livermore, a landowner whose holdings encompassed the valley. The groundwater basin underlying the...

 watershed. This subbasin is bounded to the west by the Livermore Fault Zone and to the east by the Tesla Fault

Tesla Fault

The Tesla Fault is a seismically active geological fault structure associated with the Diablo Range in the vicinity of the Livermore Valley in Contra Costa County, California.-Geology:...

. Some groundwater

Groundwater

Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

 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

Arroyo Mocho

Arroyo Mocho is a stream in eastern Alameda County, California that traverses the cities of Livermore and Pleasanton.The underlying aquifer is the Mocho Subbasin, whose eastern boundary is the Tesla Fault...

 channel across the Livermore Fault. A number of threatened and endangered species

Endangered species

An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

occur in this watershed.