SACRAMENTO, Calif. (AP) _ U.S. Interior Secretary Donald Hodel said Tuesday his proposal to restore a section of Yosemite National Park by draining a reservoir must develop a plan for an alternate water supply to make up for water that will be lost.

Hodel met with California environmentalists and public officials in a two- hour roundtable discussion he said would help resolve the issue, then left for a tour of the Hetch Hetchy Reservoir.

''Today, what we're doing is brainstorming,'' said Hodel, who repeatedly emphasized that his idea is only a suggestion that still needs extensive research to determine its feasibility.

Hodel, long at odds with the conservation movement, drew the support of environmentalists for the proposal he first made in August that the O'Shaughnessy Dam on the Tuolumne River be breached to drain the reservoir behind it.

''I think it's a good idea,'' he said about the plan. ''It would be a wonderful thing if we could restore this valley to Yosemite National Park.''

The procedure would restore Hetch Hetchy Valley, about 150 miles from San Francisco, and alleviate some of the visitor pressure on Yosemite Valley, which draws 3 million tourists a year. Hetch Hetchy Valley has been likened in beauty to a smaller Yosemite Valley.

Hodel, dressed in jeans and cowboy boots, sat in front of photographs of the late naturalist John Muir in Yosemite Valley, in a pristine state as it appeared at the turn of the century.

Leaders of San Francisco and other Bay Area communities that rely on the reservoir for their water told Hodel they will resist his proposal unless they can be ensured water of comparable purity and cost.

Hetch Hetchy Reservoir provides water to 2 million Bay Area residents.

Representatives of sporting organizations said they worry about what effects draining the reservoir may have on fishing, rafting and other recreation on the Tuolumne River.

San Francisco Mayor Diane Feinstein, who has called Hodel's proposal ''the worst idea I have heard since the sale of weapons,'' said in a statement there may be no alternative water source to the reservoir.