For the past 20 years, atmospheric scientists at Idaho Power have been seeding clouds to augment the state’s precious water supplies by wringing more snow from the sky. The company began winter cloud seeding in the Payette River watershed in 2003 to enhance winter snow accumulation at high elevations and increase summer power generation at its hydroelectric facilities.

But the benefits go far beyond generating power, and the company’s cloud seeding — in partnership with the state and water users — has extended to the Boise, Wood and Upper Snake river basins.

“Snake River Basin snowpack really is the lifeblood of our region’s economy,” said Shaun Parkinson, meteorology and cloud seeding leader at Idaho Power.

“Everyone benefits from having more water in the system — wildlife, fish, recreationists from skiers to anglers, irrigators, industry, municipalities, water managers and, ultimately, Idaho Power customers,” he said.

In the Payette Basin, Idaho Power’s longest-running project, a target-control analysis estimates the average annual increase in snowpack in seeded areas to be 10% to 12%, he said.

On average, cloud seeding increases natural river flows by about 1.24 million acre-feet annually across the four basins, he said.

That’s enough to nearly fill Palisades Reservoir, which has a capacity of 1.4 million acre-feet.

“This water is then used for a number of different uses such as irrigation diversions, aquifer recharge, reservoir storage, power production and many additional uses,” he said.

Welcomed by water users

“Idaho’s water user community recognizes cloud seeding as a tool to help bolster our state’s water supplies,” said Paul Arrington, executive director and general counsel of the Idaho Water Users Association.

“In a time when many areas of the state face water supply challenges, cloud seeding is an important arrow in our quiver,” he said.

The amount of additional water is not only a function of how much cloud seeding is able to produce but also how much snow melts and how the reservoir system is managed, Idaho Power’s Parkinson said.

“We specifically target high-elevation snowpack because that is the last water to run off in the late spring and summer, providing important streamflows at a time when irrigators and electricity customers need it the most,” he said.

The total cost of operating the three aircraft, 57 remote ground generators and weather instrumentation involved in cloud seeding is about $4 million a year. Idaho Power covers all costs associated with seeding the Payette Basin and one-third of the costs of seeding the Boise, Wood and Upper Snake basins.

The cost is about $3.22 per acre-foot of water generated, far less expensive than renting water.

Water in Idaho can be rented from Idaho Water Resource Board’s Water Supply Bank or from a rental pool, such as Water District 1. The Water Supply Bank doesn’t prevent others from selling or renting water as long as they are allowed by law. The Shoshone-Bannock Tribes also operate a Tribal Water Supply Bank.

The cost of renting water varies widely, depending on the source and the basin.

“However, even at the low end, rented water is much more expensive than what we can add via cloud seeding,” said Brad Bowlin, Idaho Power communications specialist.

Idaho Power hasn’t rented water in several years. But when it did, prices ranged from $30 to $50 an acre-foot, he said.

In Water District 1, the U.S. Bureau of Reclamation pays $17 to $25 an acre-foot to rent water for flow augmentation, he said.

How it works

Idaho Power seeds clouds by introducing additional ice nuclei in the form of silver iodide into winter storms that have an abundance of supercooled liquid water — water that is in the liquid phase and below freezing, said Derek Belstrud, Idaho Power senior atmospheric scientist.

“The additional ice nuclei increase precipitation from passing winter storm systems. If a storm has abundant water and appropriate temperatures, the conditions may be optimal for cloud seeding to increase precipitation,” he said.

Idaho Power uses two methods to seed clouds — remote ground generators at high elevations in the mountains and airplanes that burn special flares within storm clouds.

“Either method successfully releases silver iodide into passing storms. Minute water particles within the clouds freeze on contact with the silver iodide particles and eventually grow and fall to the ground as snow,” Belstrud said.

For wintertime seeding to work, there needs to be three major atmospheric components. The wind needs to be blowing in a direction that it will be forced up and over mountain ranges that are downwind from the seeding apparatus.

There also needs to be abundant supercooled liquid water, and temperatures need to be 23 degrees Fahrenheit or lower, he said.

Idaho Power uses a network of public and private weather stations and weather instruments to monitor conditions, as well as high-resolution computer weather models that forecast seeding conditions.

“Cloud seeding can only be used to increase the amount of precipitation from an existing storm. This is why we say it’s a water-management tool and not a drought mitigation tool. We can only work with water that Mother Nature is already providing,” Belstrud said.

Areas for additional snowpack can be targeted. It typically takes about 20 to 30 minutes for the seeded snowflake to grow to a size that can fall to the ground, though the temperature and amount of water in the clouds influence it.

“Understanding these variables, scientists release silver iodide from upwind locations conducive to putting additional snow in the ‘target area.’ However, the variability of these conditions preclude cloud seeding from being overly precise in where the additional snow falls,” he said.

Unintended consequences?

“Research has shown no evidence that cloud seeding in one location causes a reduction in precipitation in neighboring areas. During a storm, a relatively small portion of the overall atmospheric water falls to the ground as precipitation,” Belstrud said.

“Typically, a well-run cloud seeding program would affect less than 1% of the total available water in a storm system,” he said.

The amount of silver iodide used in cloud seeding is small and difficult to detect. Collected snow from seeding only contains a few parts per trillion of silver.

“Similar amounts of silver have also been detected from dust events where wind picks up surface dust from one location and then deposits that dust on the snowpack,” he said.

Silver iodide has been used as a seeding agent in several western states for decades without any known harmful effects. Cloud seeding has also been conducted in the Snowy Mountains of Australia, and the environmental effects of silver iodide were studied extensively and no harmful effects were found, he said.

“Silver iodide is insoluble in water, which is a characteristic that keeps it from having harmful effects, Belstrud said.

Downwind effects of cloud seeding have been found to be neutral to positive as far as generating precipitation.

Flood risks can be mitigated by suspending cloud seeding when there is adequate snowpack.

State support

After implementing a five-year cloud seeding pilot project in the Upper Snake Basin as part of the state’s Comprehensive Aquifer Management Plan, Idaho Power in 2016 approached the state about forging a long-term partnership for cloud seeding.

“So the state has really been on board since 2016, at least with the collaborative program,” said Kala Golden, cloud seeding program manager for the Idaho Water Resource Board.

That program is a partnership between the Water Board, Idaho Power and water users to fund cloud seeding in the Boise, Wood and Upper Snake river basins.

Idaho Power also funds and operates an independent cloud seeding project in the Payette River Basin, and infrastructure is shared between the programs.

At first, the Water Board provided one-time funding for capital investment and infrastructure for generators and weather instrumentation operated by Idaho Power in the three river basins.

Then it began sharing costs for operations and maintenance, which led to the development of a state program.

“Currently, the board contributes about two-thirds of the total collaborative program costs, and that’s for operations and maintenance,” she said.

The Water Board has also shared costs with Idaho Power for the development of sophisticated modeling tools.

“Those modeling tools provide forecasting and guidance for the program operation and, ultimately, once fully developed will be used to conduct ongoing analysis looking at how effective we’re being with cloud seeding,” she said.

The Water Board has contributed about $2.5 million of the $6 million to develop the modeling tools, which include a weather research and forecasting cloud seeding model as well as a hydrologic model calibrated to Idaho’s basins.

“The benefit of that is that these models can be used for things beyond cloud seeding,” she said.

For example, once fully developed they could be used to investigate streamflow in basins that don’t have snow telemetry sites.

“The state has also started some early investigative studies looking at opportunities for the development of cloud seeding projects to support other areas of the state,” she said.

Since 2017, the state has invested more than $14 million in cloud seeding operations, modeling, investigative studies, analysis and assessment. In 2021, the Idaho Legislature designated the Water Board as the state agency responsible for oversight and management of cloud seeding programs in the state.

“There’s a lot that’s been happening with our cloud seeding program the last couple of years and really industrywide if you talk to other states, other programs,” she said.

Growing interest

The principle of cloud seeding was discovered in 1946 by meteorologist and chemist Vincent Schaefer, then working in General Electric’s research laboratory in Schenectady, N.Y. He seeded clouds from an airplane with dry ice pellets and produced precipitation.

Only a few days later, colleague Bernard Vonnegut — the older brother of novelist Kurt Vonnegut — discovered the effectiveness of silver iodide to enhance the formation of ice crystals in clouds.

The technology has been used since the late 1940s to enhance precipitation and to dissipate fog and reduce the size of hailstones, Idaho Power’s Parkinson said.

“It is used all around the world and in many western states,” he said.

There’s been an explosion of interest in cloud seeding in Idaho, other states and globally, the Water Board’s Golden said.

Most would attribute that to the 2017 SNOWIE — Seeded and Natural Orographic Wintertime Clouds: The Idaho Experiment — project. It was funded by the National Science Foundation and conducted by the National Center for Atmospheric Research in partnership with Idaho Power and other universities and research organizations.

“The SNOWIE study provided the very first unambiguous evidence of the effects of cloud seeding,” she said.

The study validated what Idaho water managers already knew.

“We’ve based our program on the best available science with support from some of the most qualified individuals and entities in the industry. I think that has been instrumental in gaining support for the program,” she said.

“In terms of winter-time cloud seeding, I would say we here in Idaho operate one of the most sophisticated, advanced cloud seeding programs in the world,” she said.

That has been the result of the state’s and Idaho Power’s investments in sophisticated modeling technology and the use of cutting-edge science and information, she said.

“Certainly other states view our programs as sort of being the cutting-edge technology or the leading in the industry. We’ve been very fortunate in our state to have the support of the Water Board and the Legislature to have funding for this program,” she said.

The challenge in a lot of other states is convincing their leadership to provide funding for these programs, she said.

New technique

Idaho’s efforts to boost water supply could expand in the future. USDA Agricultural Research Service is developing a new technique to increase rainfall during warm months.

Led by Dan Martin, an ARS research engineer at College Station, Texas, researchers are seeding clouds with electrically charged water particles May through September.

Testing, which began in 2017, has shown the technique can increase rainfall by 25% to 30%.

That could mean a tall drink of water — literally — for water supplies in the thirsty West.

Average annual cloud seeding program cost per river basin:

• Payette: $870,000, funded by Idaho Power.

• Boise: $910,000, funded by Idaho Power, Idaho Water Resource Board and water users.

• Wood: $670,000, funded by Idaho Power, Idaho Water Resource Board and water users.

• Upper Snake: $1.5 million, funded by Idaho Power, Idaho Water Resource Board and water users.

Equipment

• Payette, Boise and Wood basins: 32 remote ground generators, 2 airplanes.

• Upper Snake: 25 remote ground generators, 1 airplane, 25 manual ground generators operated by the High County Resource Conservation and Development Council nonprofit.

Airplanes and pilots are contracted with Western Modification Inc.

Source: Idaho Power and Idaho Water Resource Board