Water District May Seed Clouds: Process Would Be Conducted in Upper C.V. Watershed

By Daniel Lopez, The Monterey County Herald, Calif.

Nov. 23–Faced with what is expected to be another dry winter, some water officials are considering scientific intervention to increase rainfall on the Peninsula.

The Monterey Peninsula Water Management District is exploring the possibility of conducting cloud seeding in the upper Carmel River watershed to make it rain.

The practice involves introducing an ice-forming agent such as silver iodide into cloud regions to cause supercooled liquid water droplets to freeze. Frozen, the droplets expand, producing more raindrops when they thaw.

“We are looking to eke out as much water from the clouds as we can,” said Darby Fuerst, water resources manager for the district .

He said if the right cloud systems are present, cloud seeding done from December to March could increase rainfall by 2 to 3 inches, or 15 percent to 20 percent.

While the district has never tried cloud seeding, the Monterey County Water Resources Agency has done it starting in 1990. Santa Barbara County has also practiced cloud seeding since 1950.

Monterey County’s past effort was intended to increase rainfall runoff in the San Antonio, Nacimiento and Arroyo Seco River watersheds, according to Peninsula water district staff reports. The seeding produced about 2 and 2.7 inches of additional rainfall, or between 17,000 and 22,600 additional acre-feet of water during the 1991-92 winter season, with added water stored in the San Antonio and Nacimiento reservoirs.

Fuerst said because the Peninsula

Water District’s reservoirs — the San Clemente and Los Padres — are small and normally fill on their own, they would not be good sources for storing extra water. The two reservoirs have a capacity of 70 acre-feet and 1,300 acre-feet of water capacity, respectively.

Instead, Fuerst said the target area would be the upper Carmel River watershed, with the extra water going into the river as runoff. The river supplies 70 percent of the Peninsula’s water and has been overpumped for years.

“We have drawn our resources down,” said Fuerst.

Any added rainfall produced through cloud seeding would increase flow in the river and also replenish its underground aquifer, he said.

During a year with average rainfall, Fuerst said cloud seeding could add an estimated 5,000 acre-feet of water to the river, benefiting steelhead trout, red-legged frogs and riparian vegetation as well.

Fuerst said a set of guidelines would be established so that cloud seeding would be suspended if the rainfall presented a potential for flooding.

The district is working with North American Weather Consultants, Inc., a Utah company that specializes in weather modification services, to determine the feasibility of the plan.

Fuerst said the cost of beginning a program for this winter season, December to March 2008, would cost about $150,000 for a ground application.

A ground application involves setting up hill-top stands on plots of about 10 feet by 10 feet, equipped with flares. The flares, which shoot silver iodide into the weather fronts, are remotely triggered by meteorologists who monitor storms moving through the region.

Aircraft can also be used to complete the seeding and would increase costs to about $300,000.

Fuerst said the program would begin with ground application, and then officials could decide if it should expand.

“Any increase may be helpful this year, but it may create a basis for a continual program,” said Fuerst.

Currently the district does not have any funding earmarked for cloud seeding, but Fuerst said there are funds in the Flood/Drought Reserve that could be applied.

At its regular meeting last Monday, the district board of directors asked that representatives from North American Weather Consultants make a presentation at their Dec. 10 meeting to help them make a decision.

If the district decides to go forward with the seeding, it will require further planning, possible permits and environmental analysis, and will be open to public discussion.

Daniel Lopez can be reached at 646-4494 or dlopez@montereyherald.com.

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Copyright (c) 2007, The Monterey County Herald, Calif.

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