Clouds over Los Angeles County were seeded with silver iodide to increase the amount of rainfall during Monday’s storm, marking the first cloud seeding done by the Department of Public Works since 2002.
Los Angeles County has used cloud seeding to boost water supplies since the 1950s, backing off in times of heavy rain or when wildfire devastation creates an outsized risk of flooding or debris flows.
A 2009 cloud seeding contract for services was terminated following the Station Fire, which burned roughly 250 square miles of the Angeles National Forest.
Then, last October, the state’s severe drought led the Board of Supervisors to approve a new one-year contract with Utah-based North American Weather Consultants for up to $550,000 per year.
This week’s storm offered a good opportunity for “the first go-round for cloud seeding” this season, DPW spokesman Steve Frasher said.
NAWC has set up land-based generators in 10 locations between Sylmar and Pacoima, Fraser said. Only some of those generators were used Sunday night, as weather conditions were not ideal in all areas.
The generators shoot silver iodide into the clouds, creating ice particles. Water vapor freezes onto those particles which fall as rain.
Cloud seeding cannot create clouds, but increases the amount of rainfall from existing clouds. That stormwater is then captured in dams and spreading grounds in the Pacoima, Big Tujunga and San Gabriel watersheds.
The county estimates that seeded clouds produce about 15 percent more rainfall.
Historically, cloud seeding has generated an additional 1.5 billion gallons of stormwater annually countywide, but Frasher said measurement is “between an art and a science” and impossible to precisely quantify.
A big storm with sustained rainfall is required for seeding to work, and Frasher said the next chance to build water reserves may come this weekend.
–City News Service
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