How Rheotherm Flowmeters Are Helping Make It Snow — Across the American West
As the American West faces one of the most severe water crises in modern history, an unlikely technology partnership is helping communities stretch their water supply — one snowflake at a time. For over 30 years, Rheotherm thermal mass flowmeters have played a critical role in cloud seeding operations, providing the precise flow measurement that makes weather modification possible.
What Is Cloud Seeding and Why Does It Matter?
Cloud seeding is a proven, cost-effective technique for augmenting natural precipitation. The process works by introducing silver iodide particles into clouds, where they act as ice nucleation sites — mimicking the natural process by which snowflakes form. Silver iodide’s hexagonal crystal structure closely mirrors the lattice structure of ice, causing supercooled water droplets to crystallize and fall as snow.
Over 40 million people across seven U.S. states depend on the Colorado River for water. In cities like Denver, mountain snowpack accounts for roughly 80% of the annual water supply. With reservoirs like Lake Mead reaching historic lows and seasonal precipitation becoming increasingly unpredictable, cloud seeding has emerged as one of the highest-return water management investments available — with independent economic analyses consistently finding benefit-to-cost ratios exceeding 10:1.
The Role of Flow Measurement in Cloud Seeding
Effective cloud seeding requires delivering the silver iodide seeding agent to the cloud layer at precisely the right rate. The agent is dissolved in an acetone carrier fluid and burned in a propane flame, releasing ice nucleation particles into the atmosphere. The flame temperature and carrier fluid flow rate must be maintained within a narrow range for consistent, reliable results.
This is where Rheotherm flowmeters come in.
Each cloud seeding generator uses a Rheotherm thermal mass flowmeter to continuously monitor the carrier fluid flow rate. An automated control valve responds to the flowmeter signal to hold the flow at a constant setpoint — compensating for variations in air pressure, elevation, ambient temperature, and tank fill level. Without accurate, reliable flow measurement, the entire seeding operation loses its precision and repeatability.
A 30+ Year Partnership with the Desert Research Institute
Since the early 1960s, the Desert Research Institute (DRI) has been at the forefront of cloud seeding science. Bionetics (formerly Intek, Inc.) began supplying Rheotherm flowmeters to DRI in 1991, when field technician Monte Stark outfitted a new series of cloud seeding generators. Many of those original 1991 units remained in continuous service for over 30 years — a remarkable testament to the durability of the Rheotherm design.
DRI’s technicians put it plainly:
“These flow meters have been the most crucial piece of equipment for our research needs, as they have remained robust enough to handle harsh winter temperatures (-20°F) while maintaining very precise solution flow rates… It’s truly amazing that these flow meters can sit all summer in an acetone solution, sometimes in scorching 120°F weather, and then fire right up when needed in cold Fall/Winter weather.”
Today, a team of just two DRI technicians manages over 30 cloud seeding generators spread across multiple states. Each generator produces approximately 3,000 acre-feet of snow per year. Combined, DRI’s program contributes an estimated 10,000 acre-feet annually — roughly 3 billion gallons of water added to local reserves and enough to supply 20,000 households.
Built for the Harshest Conditions on Earth
Cloud seeding generators are installed in some of the most punishing environments imaginable — exposed mountaintops in remote locations, accessible only by helicopter, buried under 8 feet of snow in winter and baking in summer heat. These conditions rapidly degrade conventional instrumentation.
Rheotherm thermal mass flowmeters are uniquely suited to these demands:
- No moving parts — nothing to wear out or freeze
- No wetted sensing elements — immune to the solvent effects of acetone over time
- Proven thermal mass measurement technology — accurate and repeatable across extreme temperature swings
- Decades of continuous service — original 1991 units survived 20+ years of unattended field operation
A Global Footprint in Weather Modification
DRI’s success with Rheotherm flowmeters led to their adoption by other cloud seeding programs worldwide:
- Snowy Hydro (Australia) — Equipped their cloud seeding generators with Rheotherm meters starting in 2003 to supplement water supply for hydroelectric generation, returning meters for annual calibration nearly every year through 2024.
- Weather Modification Inc. (Fargo, ND) — Chose Rheotherm instruments when they began manufacturing their own generators in 2006. Those meters have been in continuous operation for nearly 20 years.
- China and the UAE — Both operate major cloud seeding programs, as climate variability drives global investment in weather modification technology.
Active programs now run in more than a dozen U.S. states, managed by water utilities, ski resorts, and power authorities. As climate pressure intensifies, demand for proven, reliable cloud seeding instrumentation will only grow.
Precision Where It Counts
Cloud seeding is not a silver bullet for the water crisis — but it is a proven, scalable, and cost-effective complement to conventional water management. The science only works when the instrumentation works. For over 30 years, Rheotherm flowmeters have delivered the measurement accuracy and field durability that demanding cloud seeding environments require.
Want to learn more? Download our full Application Focus document: Rheotherm Application Focus – Cloud Seeding
Or contact our team to discuss your flow measurement application.
Related reading: