Denver Water wants to know if cloud-seeding works

Brief by Central Staff

Weather – November 2003 – Colorado Central Magazine

Does cloud-seeding really work? Or would any extra snowfall have happened anyway?

Last winter, as Colorado struggled with a drought, cloud-seeders were set up in the mountains. They have chimneys that shoot silver-iodide particles upward, into the clouds. In theory, the small particles provide a place for water molecules to coalesce into snowflakes, which then fall.

Denver Water, which supplies most of the metro area, spent $700,000 last winter on seeding for about 6,500 square miles in the water system’s catchment zone. Other water agencies, as well as several ski resorts, also contributed to the seeding cause.

Last summer, the agency commissioned two studies to determine whether the money was well spent. One study examined 10 sampling sites, and in nine of those sites, there were low concentrations of silver iodide; this indicates that the snow did not result from cloud-seeding.

But another study, based on statistical analysis of snowfall records, show a 14% gain in water content, and a 17% gain in snowfall, in those areas where the clouds were seeded.

“We will be trying to figure this out,” said Steve Schmitzer, chief of water resources analysis for Denver Water, before deciding on cloud-seeding for the winter of 2003-04.

Meanwhile, at a Sept. 30 Water Summit in Leadville, Lake County officials noted that if cloud-seeding worked, it raised local costs for plowing roads, even though the water didn’t belong to the county.

Terry Scanga, general manager of the Upper Arkansas Water Conservancy District, said that future cloud-seeding agreements should include some funds for snow removal in Lake County.

That’s a problem that counties to the south might like to have. Although the northern and central drainages had snowpacks near or above average last winter, the Rio Grande drainage and the San Juans are still suffering from drought.