This water supplies irrigation in the Valley, etc... The complex has many missions. Water supply, hydroelectric, flood control, recreation, environmental, etc...
This dam,like many others was more than likely designed for flood protection primarily after some apocalyptic flooding in the 1950s where the flooding was the heaviest on record. I know that sounds bizarre considering the bad drought the state has been in, but it wasn't always that way.
I understand your idea - they'd essentially need to pump it to above ground or below ground storage tanks.
What you are yalkinge about is called "pumped storage" when dealing with hydroelectric. I am sure they do it in Cali for water supply... Somewhere? But it all races down elevation to the cities by the sea anyway. Water just travels down aqueducts & canals. In Oroville's case, starting @ the Feather river. Water can even go uphill in spots without pumps, if it continues on downhill. I think Mulholland devised a system out of Owens Valley to supply LA @ turn of 20th century? Water from Lake Oroville goes all the way to Los Angeles too. Helps supply them as well.
In our neck of the woods, pumped storage is used for power generating... Like here @ Kinzua:
Edited by ExiledInIllinois, 13 February 2017 - 01:44 PM.