Beginning a new chapter in one of America's oldest conservation battles, environmental groups Monday are expected to turn in enough signatures to qualify a November ballot measure in San Francisco that would require the city to draw up a plan to drain Hetch Hetchy Reservoir.

The reservoir in Yosemite National Park and the Tuolumne River that flows into it are the main water source for 2.5 million Bay Area residents who live in San Francisco or on the Peninsula, as well as in parts of San Jose and Alameda County....