At any time when there’s a massive storm within the western United States, pilots are prone to fly into the attention and see clouds containing a substance referred to as silver iodide. The aim is to extend rainfall.
Cloud seeding has been round for the reason that Nineteen Forties. It has grow to be widespread of late because the West struggles with a drought of historic proportions. Governments, utility corporations and even ski resorts are footing the invoice.
Though it was assumed to be efficient for many years, latest research have helped show that cloud seeding works and there’s no proof that silver iodide is dangerous at present ranges. Consultants say cloud seeding typically produces a 5% to fifteen% improve in precipitation.
There isn’t any remedy for drought, however cloud seeding might be an essential water administration instrument.
“We won’t make storms occur and we won’t create situations on this storm which can be perfect. They occur naturally,” mentioned Jason Carkeet, utility specialist and hydrologist with the Turlock Irrigation District in central California. Turlock began its cloud seeding program in 1990.
“What we’re doing is simply taking benefit of the present situations, the pure situations, and attempting to make the storm once more extra environment friendly from a water provide standpoint,” Carkeet mentioned.
How cloud seeding works
When executed from the air, cloud seeding entails loading an plane with silver iodide. Flares are positioned on the wings and fuselage.
The pilot reaches a sure altitude, the place the temperature is right, and shoots the flares into the cloud. The silver iodine causes particular person water droplets throughout the clouds to freeze collectively and type snowflakes, which finally grow to be so heavy that they fall.
Away from the freezing course of, the droplets wouldn’t coalesce and grow to be massive sufficient to fall as rain or snow.
“The cloud is initially all water,” mentioned Bruce Boe, vp of meteorology at Climate Modification Worldwide, a non-public firm that has supplied cloud seeding providers since 1961. “Finally, by the point it will get to the highest of the mountain, it might doubtlessly be 50% ice or possibly greater than that. Besides, there may be nonetheless lots of liquid water left there.”
Boe mentioned there is a “window of alternative” to get the precipitation sufficiently big to fall “earlier than it hits the mountain and begins to descend and heat up.”
Pilot Joel Zimmer, who works for Climate Modification Worldwide, attaches a silver iodine flare to the underside of a cloud seeding aircraft.
Katie Brigham | CNBC
For cloud seeding pilots like Joel Zimmer, who works with Climate Modification Worldwide to seed clouds for the Turlock Irrigation District, flying into the storm might be an thrilling however intense expertise.
“As soon as the wheels are up, you are within the clouds,” mentioned Zimmer, whose route consists of seeding throughout the Sierra Nevada mountains. “And we’re in a cloud the entire mission till we’re flying the strategy again into the airfield after which we shoot out of the clouds and have a view of the runway. It feels such as you’re a lieutenant within the Navy. You do not see something.”
From a water provide viewpoint, it’s most respected to seed clouds over mountains, the place the water is definitely saved as snow till the spring runoff.
“When it is out within the plains like North Dakota, it is nonetheless a profit as a result of it helps recharge the soil moisture,” Boe mentioned. “However it could’t be saved and used later.”
Whereas Texas makes use of cloud seeding to assist farmers irrigate fields, it is extra widespread within the West, the place states like Idaho, California, Colorado, Utah and Wyoming use it to assist refill their rivers and reservoirs. Most applications use plane for cloud seeding, however some use floor flares.
“It is much more widespread than folks assume,” Carkeet mentioned. “Extra reservoirs have seeding applications than non-seeding applications.
Value and affect
Boe says the fee is nearly all the time value it.
“It makes lots of sense for water managers to go forward and do this, even when the rise is a number of proportion factors,” he mentioned.
Idaho Energy spends about $4 million a 12 months on its cloud seeding program, which produces an 11% or 12% improve in snowpack in some areas, leading to billions of gallons of further water at a value of about $3.50 per acre-foot. That compares to about $20 per acre-foot for different strategies of accessing water, corresponding to by way of water provide banks.
And whereas Turlock will solely see a 3% to five% improve in runoff from its plan — which has a most price of $475,000 — California will take all the additional water it could get.
“That is one of many issues that makes it so arduous to quantify, you do not see a doubling or tripling of precipitation,” Boe mentioned. “You see a rise, however add it up over the winter after which it could grow to be important.”
Watch the video to be taught extra about what it takes to make it rain.