A controversial rainmaking technique once used as a top-secret weapon of war is now routinely carried out in southern San Luis Obispo County by the Santa Barbara County Water Agency.

Known as cloud seeding, the operation involves launching a rainmaking chemical into storm clouds, with the idea of augmenting the water supply in Twitchell Reservoir and the Santa Maria groundwater basin.

PHOTO COURTESY OF NORTH AMERICAN WEATHER CONSULTANTS

PYROTECHNIC PRECIPITATION : Flares resembling fireworks—complete with spark arresters—are set to launch silver iodide into winter storm clouds to increase rainfall in Santa Barbara and San Luis Obispo counties.

Successful tests on local storm clouds conducted by the U.S. military in the 1960s and ’70s were used for a more sinister purpose, however: warfare. American forces carried out secret aerial cloud-seeding operations designed to wash out the Ho Chi Minh Trail with heavy monsoon rains in North Vietnam, from 1967 until 1972. Cloud seeding as a weapon of war was subsequently banned by international treaty.

Santa Barbara County has been seeding storm clouds with silver iodide nearly every winter since 1981, both from mountaintop stations and from airplanes. The chemical makes water droplets in clouds artificially condense into ice that falls as rain—or so the theory goes.

The water agency’s rainmaking program has targeted the Huasna Valley area in southern SLO County—part of the Twitchell Reservoir watershed—since 1992.

But the scientific community is divided on the effectiveness of cloud seeding. The National Academy of Sciences has concluded “there is still no convincing scientific proof of the efficacy of intentional weather modification efforts.”

That hasn’t stopped Santa Barbara County supervisors and water districts from approving a cloud-seeding program year after year. Last winter’s operation cost $310,000, while a reduced program for the upcoming winter has a budget of around $120,000, with North American Weather Consultants of Sandy, Utah, contracted for the work. The contract is due for approval

by Santa Barbara County supervisors in early November.

Proving conclusively that the silver iodide seeding technique actually produces more precipitation than would otherwise have fallen downwind is a challenge, according to a report to Santa Barbara County supervisors by cloud-seeding contractors North American Weather Consultants. Mountainous regions are considered the

best bet for success.

A naval weapons laboratory’s research results from decades ago, known as “Santa Barbara II,” concluded that rainfall was increased over a large area of SLO and Santa Barbara counties from ground-based silver iodide flares and from airplane wingtip silver iodide generators. Research conducted in San Luis Obispo and Santa Barbara counties by the Naval Weapons Center in China Lake, Calif.—along with its contractor North American Weather Consultants—was applied to top-secret weather warfare against the North Vietnamese from 1967 to 1972.

“The [local] program has an interesting background,” North American Weather Consultants President Don Griffith said in a phone interview from his office in Utah. “[It] was a trial for some of the technologies they were developing.”

Although the Vietnam War rainmaking program was initially denied by the U.S. defense secretary, the American military eventually admitted flying more than 2,600 missions to drop silver iodide into storm clouds over North Vietnam, code-named Operation Popeye.

“We regard the weather as a weapon,” Naval Weapons Center admiral Pier Saint-Amand told the U.S. Senate in 1972, once the cloud-seeding missions became public—and were discontinued—after reports in the Washington Post and The New York Times.

At the time, Sen. Claiborne Pell, chairman of the Senate Foreign Relations Committee, said, “Rainmaking as a weapon of war can only lead to the development of vastly more dangerous environmental techniques whose consequences may be unknown and may cause irreparable damage to our global environment. This is why the United States must move quickly to ban all environmental or geophysical modification techniques from the arsenals of war.”

An international treaty prohibiting weather warfare, the Environmental Modification Convention, came into effect

in 1978.

These days, with many countries carrying out cloud seeding and other weather modification techniques, a World Meteorological Organization report states, “The implications of any projected longterm weather modification operation on ecosystems need to be assessed.”

For this winter’s cloud-seeding program, the Santa Barbara County Water Agency will set up pyrotechnic silver iodide flares on a ridge near Santa Maria, aimed at storm clouds moving into SLO County and northern Santa Barbara County. Known as AHOGS—for automated high-output ground-based seeding—the flares will be remotely detonated by computers in North American Weather Consultants’ offices in Utah using a cell phone Internet connection. Timing of the firing will be guided by weather information that computers will receive from radar stations at Vandenberg Air Force Base.

According to the water agency’s senior hydrologist, Dennis Gibbs, rainfall in the Huasna Valley is likely to increase at least 10 to 15 percent because of the cloud seeding, helping to fill Twitchell Reservoir.

“It’s the cheapest source of water. We’re not taking anybody else’s rain. We’re giving nature a helping hand,” Gibbs said.

And in major storms that could create flooding, the cloud-seeding contract now contains a provision allowing the project meteorologist to suspend the automated firing of the silver iodide flares to reduce the risk of floods.

Still, some people in SLO County are questioning the Santa Barbara County Water Agency’s plans.

“My problem is that I don’t know if it works, or where else the rain would have fallen,” said Michael Winn, a director of the Nipomo Community Services District and a longtime member of the SLO County Water Resources Advisory Committee. “If they’re not taking water that otherwise would have fallen somewhere else, cloud seeding doesn’t work. You can’t have it both ways. I’d like to see serious studies over 20 or 30 years, on what happens when you do and don’t seed.

“I just want to make sure it’s done carefully, with controls, before blanketing the whole coastal range of San Luis Obispo County with silver iodide,” Winn said.

For others, it’s the overall management of the planet’s atmospheric water resources that’s an important issue.

As political observer and SLO County Water Resources Advisory Committee member Eric Greening told SLO County supervisors recently, “I think the whole issue needs study and maybe a big slowdown. Our involuntary and still uncontrolled effects on the climate are bad enough without deliberately trying to change the climate, too.”

Contributing writer Kathy Johnston can be reached at kjohnston@newtimesslo.com.