Cloud Seeding Begins in the Sierra

By Alex Breitler

From his offices in Fresno, Steve Johnson explained how cloud seeders spent one of the driest Januaries on record:

"We’d look at the forecast maps and pray," he said.

Johnson’s planes are soaring over the Sierra Nevada once again this week, scattering silver iodide particles to squeeze just a bit more snow out of some long-awaited storms.

The twin-engine planes have been frozen to the ground for the most part this winter, said Johnson, general manager of Atmospherics Inc., a "weather modification" company. Cloud seeding is no use if there aren’t any clouds.

When conditions are right, however, cloud seeding across California can bolster the state’s runoff by perhaps 3 percent to 4 percent. And that could be important this year, with the snowpack in the Sierra Nevada a measly 40 percent of normal.

Right now, the state would need about double its normal precipitation for the rest of the winter and spring to catch up, said Department of Water Resources hydrologist Maury Roos. Cloud seeding won’t do it alone, but it can help.

"When you get into a dry year, every drop is valuable," Roos said.

Experiments with cloud seeding began in the 1940s; today there are about a dozen programs to enhance precipitation, mostly snowfall in the mountains.

Utilities that depend upon spring runoff to produce energy are some of the main sponsors. Pacific Gas and Electric Co. seeds clouds in the upper Mokelumne River headwaters; the Modesto Irrigation District seeds the upper Tuolumne River watershed.

"Cloud seeding is not going to make up the deficit we have now — we have to have some storms," said Arlen Huggins, whose Reno-based Desert Research Institute seeds clouds using remotely operated ground units.

But there may be more potential than the state has estimated: Huggins said small cloud-seeding research projects have shown precipitation can increase as much as 50 percent.

Throughout California, cloud seeders sow about 13,000 square miles, an area nearly 10 times the size of San Joaquin County. The cost is about $3 million, making cloud seeding one of the cheaper ways to increase water supplies, compared with building dams and reservoirs.

Seeding generates about 300,000 to 400,000 acre-feet of extra water, enough to cover the city of Stockton 8 to 10 feet deep, reports say.

With the exception of far Northern California, there are few mountainous regions that aren’t already targeted by cloud seeders, so there is little room to expand geographically. On the other hand, few of the cloud seeders likely have enough equipment to cover all their territory, said the research institute’s Huggins.

The practice doesn’t enjoy unanimous support. The Northern California Power Agency’s plan to cloud seed the upper Stanislaus River beginning this year met protests from environmentalists.

The Central Sierra Environmental Resource Center was concerned about altering weather over designated wilderness areas and what effect the silver particles might have on declining frog populations. Cloud-seeding operations are only lightly regulated by the state; no permits are required, but seeders must inform the Department of Water Resources of their plans.

But state reports say silver has fairly low toxicity and that the amounts released in cloud seeding can’t compare with exposure from industrial emissions or even tooth fillings.

Johnson’s Fresno-based company uses a radar station in Modesto to track storms and conditions such as wind speed, direction and temperature. An employee there can direct pilots toward the most promising precipitation.

"Our clients need the water," Johnson said. "The state of California needs the water."

Contact reporter Alex Breitler at (209) 546-8295 or abreitler@recordnet.com.