William Mulholland, the civil engineer responsible for the Owens Valley - LA aquaduct, traced the flow of subterranian water from the Owens valley to the LA basin. He dropped a radioactive isotope tracer in to Owens lake and the activity shoed in the ground water of Los Angeles.
For the last 75 years, anybody who has a well in the LA basin owes the LA Dept of Water and Power a fee based on the production of that well,as Mulholand showed that the water was from the Owens Valley, and those watr rights were owned by the LADWP.