California Code, Water Code - WAT § 13710

“Well” or “water well” as used in this chapter, means any artificial excavation constructed by any method for the purpose of extracting water from, or injecting water into, the underground.  This definition shall not include:  (a) oil and gas wells, or geothermal wells constructed under the jurisdiction of the Department of Conservation, except those wells converted to use as water wells;  or (b) wells used for the purpose of (1) dewatering excavation during construction, or (2) stabilizing hillsides or earth embankments.