Cloud seeding has been conducted off and in the central Sierra — including the north fork of the Stanislaus River — since the 1950s.
The 80-year old technology is now in the crosshairs of Congress Member Marjorie Greene who wants to outlaw it in the wake of deadly flooding along the Guadalupe River in Texas that she contends had to do with cloud seeding.
As of March, 25 states had legislative proposals to outlaw cloud seeding spurred by theories circulating on social media long before at least 131 people died in flash flooding in Kerrville, Texas.
California is not among the states seeking a ban supposedly because cloud seeding can cause catastrophic flooding.
There have been some groups, including the National Park Service responsible for the 1,169 square miles within Yosemite National Park, seeking to end the practice due to concerns the chemicals used can cause damage to ecological systems.
The California Department of Water Resources’ latest published study on “precipitation enhancement resource management” references previous research that notes winter orographic cloud seeding can improve precipitation between 4 and 15 percent.
Orographic cloud seeding is where wind blows over a mountain range causing clouds and rain or snow to fall by lifting the air.
It is an entirely different process than what is used in areas such as Central Texas.
A 1992 baseline study about cost effectiveness placed the cost of “new” water produced at $50 per acre foot in terms of the drought water bank measurement at the Delta.
That water, accounting for conveyances losses and such, was marketed at $70 to $75 per acre foot.
There are 16 general areas where cloud seeding typical takes place in California primarily in the central and southern Sierra and parts of the Coastal Range.
There are more done in drought years with the number tapering off to a dozen or so in normal or wet years.
In the 1990s when a cloud seeding flight over Yosemite on behalf of the Turlock and Modesto irrigation districts was conducted, the park service demanded they be stopped due to concerns of the potential impact of silver iodide.
The Department of Water Resources cites research that shows 50 years of off and on cloud seeding on the Mokelumne River watershed basin by PG&E and by water agencies elsewhere indicated “continued (cloud seeding) operations should not result in any significant chronic effect in sensitive aquatic organisms.”
The department has recommended the state step up cloud seeding efforts including trying to find chemicals that would allow the process to succeed at higher temperatures.
The DWR report states, “weather modifications projects are vital resources to enhance fresh water supply for communities within their watersheds. Additional surface water supply helps to cope with the ongoing droughts and to suppress wildfires.”
As such the agency wants to see stepped up state support of cloud seeding as one of the answers to meeting California’s ongoing water needs.
Locally, besides the North Fork of the Stanislaus River, cloud seeing takes place over the Tuolumne River watershed.
None of the clouding seeding involves the South San Joaquin Irrigation District that operates the Tri-Dam Project on the Middle Fork of the Stanislaus River in conjunction with the Oakdale Irrigation District.
To contact Dennis Wyatt, email dwyatt@mantecabulletin.com
