After traversing the cities of Livermore and Pleasanton it joins South San Ramon Creek to become Arroyo de la Laguna, which in turn flows to Alameda Creek and thence to San Francisco Bay.

[5] Frank Latta, in his book on Joaquin Murrieta, says it got its name from the nickname of the man who ran the Murrietta gang's water stations and holding corrals in this area along La Vereda del Monte, the route of their drives of captured mustangs and stolen horses to the south.

[10] Arroyo Mocho originates on the western slope of 3,684 feet (1,123 m) Mount Mocho[2][5] in the far northeast corner of Santa Clara County[11] and flows west to Mines Road which it follows northwest into Alameda County.

[12] Although historically it sank into the area between Livermore and Pleasanton now the site of multiple gravel pits, there is an engineered channel connecting it to Arroyo de la Laguna.

[14] Elevations in the Arroyo Mocho basin are between 60 and 1200 meters; mean annual precipitation is 428 mm on average.