Glen Tootle

UTK civil and environmental engineering

Cloud seeding, a close relative of rainmaking, has something of a “sleight of hand” reputation.

Still, with increasing populations in Utah, Arizona, Colorado, Wyoming, Idaho, and Nevada, not to mention California’s ever-present agricultural demands, arid western states spend millions of dollars a year on cloud seeding projects.

"But, the question of the day," says JDRD team leader Glen Tootle, "is, does it work?"

In 2006, the state of Wyoming set out to find the answer through an $8.8 million cloud seeding project, targeting snowfall in the Sierra Madre and Wind River mountain ranges. Both feed the North Platte River basin and provide excellent locations for ground-seeding and experimental-control areas.

"The increase doesn’t have to be huge to be significant," Tootle says. "Basically, cloud seeders will tell you the increase will fall within the general range of snow fall; maybe a 5, 10, or 15 percent increase."

Tootle says the project is unique. Unlike other seeding projects that put all the money into operations, Wyoming hired the National Center for Atmospheric Research (NCAR) to conduct an independent study to determine whether snowfall levels were the result of seeding or would have occurred anyway.

Tootle and companion LDRD project leader Aroop Ganguly have joined forces to help NCAR determine if an increase in snow will actually make any difference to the ranchers, farmers, or anyone else in the watershed who goes to the tap for a drink of water.

"Especially given the consensus in the scientific community that temperatures are on the rise," Tootle says.

It will be some time before data are available from the Wyoming project. In the meantime, Tootle and the team are running preliminary computer scenarios “to see how a one-half degree Celsius rise in

JDRD Project: Adaptation of water resource systems to climate change through weather modification;
LDRD Project: Uncertainty assessment and reduction for climate extremes and climate change impacts, Auroop Ganguly.

temperature every 10 years and a 2 percent, 5 percent, or 10 percent increase in snow pack might affect stream flow.

"Many people have played the game of increasing or decreasing temperatures or precipitation to see what happens to stream flow, but what makes this a nice scientific contribution is adding weather modification to our scenarios," Toole says.

Tootle says the project also has far-reaching potential in the Tennessee Valley, where increasing temperatures and flat-line precipitation could alter water supplies and hydroelectric power.

The Study Area: The North Platte river is a 680 miles long tributary of [the] Platte river that collects water from the North Platte Headwaters watershed in Colorado and Upper North Platte watershed in Wyoming. North Platte Headwaters watershed is surrounded by Elkhead, Rabbit Ears, and Laramie mountain ranges whereas Upper North Platte watershed has Sierra Madre and Medicine Bow mountains in the west and the east, respectively . . . . [The] North Platte river feeds lake Simona located north of the basin. [In figure above:] (a) Western United States show location of North Platte basin. (b) North Platte basin . . . showing tributaries and snow augmentation mountain ranges.

Graphic and caption from: “Weather Modification and Climate Variability Impacts on Streamflow” by Haroon Stephen, Glenn Tootle, Cody Moser, and Oubeid Aziz: AWRA5 2009 Spring Specialty Conference, Anchorage, Alaska, May 4-6, 2009.