SAN FRANCISCO — Flying over the Sierra Nevada as California entered its fourth year of drought, the state’s energy chief looked down and saw stark bare granite cloaked in dirty brown haze — not the usual pristine white peaks heaped with snow that would run the state’s hydroelectric dams for the year.

California’s historically low snowpack is a meager accumulation with serious implications not only for the state but potentially for the entire West if the drought persists.

Snowpack at 12 percent of average in the Sierra Nevada means less runoff to feed rivers and streams that run through dams to generate clean hydroelectric power. Despite the state’s ambitious clean-air goals, officials are turning to dirtier, more costly fossil-fuel plants to fill some of the gap. They also will seek hydro power imports from a region expected to have markedly less to offer this summer.

At a minimum, “we’ll keep the lights on,” said Robert Weisenmiller, chairman of the California Energy Commission. “We’re not concerned about not having power.”

“What we’re concerned about,” he said, “is, the power is going to come from different sources not as benign” for the health of people and the environment as hydro.