Over the last few decades, both commercial and residential water users have made huge strides in increasing efficiency. Still water experts writing for the Public Policy Institute of California say the state has work to do to protect the water supply from future disruptions.
For example, the Delta provides about 30 percent of southern California's water, yet the report says an earthquake could put this water source out of commission for up to two years.
Also, scientists predict that rising temperatures will reduce the state's natural water storage in the Sierra Nevada snowpack.
As snowpack shrinks, groundwater basins will become even more important. Yet the report notes the state currently doesn't track groundwater use -- even though it's about one-third of overall water use.
The authors recommend improving groundwater management, and modernizing how we measure and price water in the state. And they say improving environmental management of water would benefit many of the state's ecosystems-- and its citizens.