An hour’s drive northeast of San Francisco lies California’s most important water source and the West Coast’s largest estuary. Stretching across 1,100 square miles and five counties, the Sacramento-San Joaquin River Delta and its dozens of manmade islands support a $5 billion agricultural industry and supply water to over 25 million Californians. But the Golden State’s endless thirst and population growth has the delta on the brink of ecological disaster, experts predict. Decades of overpumping, agricultural runoff and tepid water temperatures have nearly extinguished a once-booming salmon population and polluted water quality.