SAN FRANCISCO (Reuters) - A new survey of California winter snows on Thursday showed the most populous state is facing one of the worst droughts in its history, Governor Arnold Schwarzenegger said.

The state, which produces about half the United States' vegetables and fruit, is in its third year of drought and its main system supplying water to cities and farms may only be able to fulfill 15 percent of requests, scientists said.

The snowpack on California's mountains is carrying only 61 percent of the water of normal years, according to the survey by the state Department of Water Resources. Last year the snowpack held 111 percent of the normal amount of water, but spring was the driest ever recorded.

"California is headed toward one of the worst water crises in its history, underscoring the need to upgrade our water infrastructure by increasing water storage, improving conveyance, protecting the (Sacramento) Delta's ecosystem and promoting greater water conservation," Schwarzenegger said in a statement.

"We may be at the start of the worst California drought in modern history," added Water Resources Director Lester Snow in a separate statement.