How cloud seeding helps replenish western reservoirs

Whenever a major storm hits the western United States, pilots fly in and sprinkle clouds with a substance called silver iodide.The goal is to increase precipitation.

Cloud seeding has been around since the 1940s. It’s been spreading lately as the West battles a drought of historic proportions. States, utility companies and even ski resorts are paying the bills.

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Although it has been proven to be effective for decades, Recent research It helps prove that cloud seeding works and there is no evidence that silver iodide is harmful at current levels. Experts say cloud seeding typically increases precipitation by 5-15% Let

While not a cure for drought, cloud seeding can be an important water management tool.

“We can’t make storms and we can’t create ideal conditions in this storm. They just happen naturally,” said Utilities Analyst and Hydrology for Turlock Irrigation District in Central California. said Jason Kurquito, Turlock started his cloud seeding program in 1990.

“What we’re doing is just taking advantage of existing conditions, naturally occurring conditions, and trying to make storms more efficient in terms of water supply,” Khakeet said.

If done in the air, cloud seeding requires loading silver iodide onto the plane. Flares are placed on the wings and fuselage.

The pilot reaches a certain altitude where the temperature is ideal and fires a flare into the clouds. Silver iodide freezes individual water droplets in clouds together, forming snowflakes that eventually become so heavy that they fall.

Without the freezing process, the droplets would not coalesce and become large enough to settle out as rain or snow.

Bruce Boe, vice president of meteorology at Weather Modification International, a private company that has been providing cloud seeding services since 1961, said: It may be 50% ice or more, but even if it is, there’s still plenty of liquid water left in it. ”

Bo said there is a “window of opportunity” for precipitation to be sufficiently high “before it reaches the top of the mountain and begins to descend and warms up.”

For cloud seeding pilots like Joel Zimmer, who works with Weather Modification International to seed the Turlock Irrigation District, flying through a storm can be an exhilarating but intense experience.

Zimmer, who follows the seeding route across the Sierra Nevada, said: “And then you’re in the clouds the entire mission until you shoot the approach to the airport, and then you pop out of the clouds and you get visibility on the runway. You feel like a navy second-in-command. What do you I can’t see it either.”

From a water supply perspective, it’s most valuable to plant clouds over mountains where water is basically stored as snow until spring runoff.

“Even when you’re in plains like North Dakota, it’s still beneficial because it helps recharge the soil’s moisture,” Bo said. you can’t.”

Texas uses cloud seeding to help farmers irrigate their fields, while states like Idaho, California, Colorado, Utah and Wyoming use cloud seeding to fill rivers and reservoirs with water. is used for Most programs use airplanes for cloud seeding, but some programs use ground-based flares.

“It’s much more common than people think,” says Carkeet. “There are more basins with seeding programs than without seeding programs.”

Boe says the cost is almost always worth it.

“Even if the increase is only a few percentage points, it makes a lot of sense for water managers to go ahead and do it,” he said.

Idaho Power spends approximately $4 million annually on its cloud seeding program. This would increase snow cover by 11% or 12% in some areas and add billions of gallons of water at a cost of about $3.50 per acre-foot. This compares to about $20 per acre-foot for other methods of accessing water, such as through a water bank.

And while Turlock sees only a 3% to 5% increase in runoff from its program (with a maximum budget of $475,000), California uses all the extra water it gets.

“One of the reasons it’s so difficult to assess is that we don’t see doubling or tripling of precipitation,” Bo said. When you add it all up, it can add up to quite a lot.”

Watch the video to learn what it takes to make it rain.