KPBS: An environmental group has listed a California river as America’s most endangered river. The river is one of the main sources of water for San Diego and millions of Californians. KPBS Reporter Ed Joyce has the story. The Sacramento and San Joaquin Rivers funnel water through the 1,000 square mile Delta, a web of channels and islands that forms the hub of California’s water system. Steve Rothert with American Rivers says the Sacramento-San Joaquin River system is on the verge of …