California's water is limited and putting politics aside, we desperately need to manage this finite resource. Aggressive conservation is one small step in that direction. This plan aims at reducing the per capita use from 192 gallons per capita per day to 154 gallons per capita per day, which in my opinion is a decent start, considering the state of water consumption in the US and the world.
Through Metropolitan Water District of Southern California, San Diego County imports up to 90% of it's water from the Colorado River and Northern California (see figure below). The remaining 10% is pooled together from local water sources like groundwater, surface water, recycled water, seawater desalination and conservation.
Courtesy: Marsi Steirer, San Diego Public Utilities Department
While conservation is key to sustainable water management, it cannot be the ultimate answer. The key is having a varied portfolio of sustainable supply choices, including the use of greywater and recycled water.