Members of the Wyoming Legislature’s Agriculture, State and Public Lands & Water Resources Committee heard a multi‑hour briefing on cloud seeding on behalf of the Wyoming Water Development Office and university and contractor partners. Presenters described the meteorological basis for glaciogenic (winter) cloud seeding, how Wyoming’s program has operated, and environmental monitoring that has accompanied the work. The briefing also recapped this year’s budget actions that ended state funding for airborne operations and limited ground operations to projects fully funded by non‑state sponsors.

The Water Development Office said Wyoming’s program presently relies on 13 ground generators: 10 targeting the Wind River Range and 3 targeting the western slopes of the Sierra Madre Range. Staff described an operational season that typically runs from early November to mid‑April and 24/7 forecasting and monitoring when operations are active. In 2024–25, staff reported roughly 177 hours of seeding events called for the Wind River Range and about 230 seeding event hours for the Sierra Madres; total “generator hours” (generators running multiplied by hours active) averaged roughly 1,071 per winter in the Wind River Range across multiple seasons, officials said.

University researchers explained the physical idea behind winter cloud seeding: when clouds contain “supercooled” liquid droplets at temperatures just below freezing, introducing ice‑nucleating particles (typically silver iodide in glaciogenic programs) can cause ice crystals to grow at the expense of supercooled liquid, producing more snow. University of Wyoming staff reviewed recent observational campaigns (for example ‘‘SNOWIE’’) that combined aircraft, ground radar and numerical modeling. Researchers said the field experiments demonstrated localized signatures consistent with seeded plumes and that model‑based seasonal evaluations give an estimated positive but case‑dependent signal. Scientists cautioned that statistical proof from random tests alone is challenging because of natural variability, and that robust conclusions require physical observations and model evaluation across many cases.

Environmental contractors and laboratory staff addressed chemical concerns, describing trace‑chemistry monitoring protocols and long‑term baseline sampling in snow, stream water and sediments. They reported that silver concentrations attributable to seeding are typically measured in parts per trillion — many orders of magnitude below natural crustal levels reported for soil and sediments (parts per million to parts per billion). They also described the chemical behavior of silver: silver ion (Ag+) is the toxic form in laboratory tests but is not the dominant species released from silver iodide under typical field conditions, and most total silver in soils and sediments is already present from natural mineral sources. Speakers described permitting steps taken previously (environmental assessments, temporary use permits for state land, reporting requirements to NOAA and the Wyoming State Engineer for operations).

Presenters summarized cost/benefit numbers drawn from prior Wyoming and regional studies. The Water Development Office cited one hydrologic assessment of Medicine Bow–Sierra Madre that reported an ensemble mean cost of about $60 per acre‑foot for the precipitation seeding effect and about $81.87 per acre‑foot for the modeled streamflow effect; earlier pilot studies were cited with broader ranges (roughly $35–$124 per acre‑foot depending on methods and the season analyzed). Officials emphasized the difference between single‑storm impacts and seasonal or multi‑season water yield, and they noted that accurate season‑scale estimation requires detailed observations and model calibration.

Committee members asked about who pays (Wyoming said the legislature removed statewide funding for aircraft and ground operations in 2025 and allowed ground‑based operations only if fully funded by Colorado River water users or other sponsors), about downstream or “rob Peter to pay Paul” effects, and about gaps in instrumentation and evaluation. Utah and other state speakers described their larger, modernized programs and an ongoing field campaign (Snowscape) aimed at better calibrating models with radiometers, gap‑filling radars, aircraft and drone trials. Several presenters recommended continuing rigorous observational campaigns and improved instrumentation to reduce uncertainty.

At the meeting’s close the committee voted to ask the Legislative Service Office (LSO) to draft a cloud seeding moratorium and baseline study bill for committee consideration — the motion to request a draft was approved by the committee. The committee separately requested a draft joint resolution on broader atmospheric experiments; that resolution draft was also approved for preparation by LSO.

Why it matters: Wyoming officials and water users framed cloud seeding as one tool in an upper‑basin effort to augment flows into the Colorado River system. The program’s proponents argue modest, repeatable gains across seasons may help manage water shortages; opponents and some public commenters said uncertainty about environmental and public‑health effects requires stricter limits or a moratorium until more data are available. The committee’s vote to request LSO drafts means both options — further regulation and moratoria or continued program operations with more monitoring — will be examined in bill form.

Ending note: Presentations emphasized both the technical limits (cloud physics, case dependency) and the need for stronger observational data if the state is to make definitive, long‑term policy choices about cloud seeding.