Arroyo Seco is an 11.7-mile-long (18.8 km)[2] watercourse in Alameda County, California, that traverses through the city of Livermore, emptying into Arroyo Las Positas.

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.

[3] A number of threatened and endangered species reside in this watershed.

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