If you’ve been following our blogs for a while, you probably know that our partner agencies rely on both local and imported water to meet the needs of customers in our region. We are constantly looking for ways to optimize our water supply to ensure that there is water now and for generations to come. One approach that has been useful in other parts of the State, country, and around the world to augment local water supplies is cloud seeding. We’re here to break this down in simpler terms and clue you in on an innovative initiative for our region’s watershed.
What is cloud seeding?
Cloud seeding is used to increase the amount of precipitation in the form of snow or rain during storms in higher elevation target areas to supplement local water supplies. Stormwater is captured in groundwater basins in the watershed.
SAWPA conducted a Feasibility Study (study) to assess the potential benefits of cloud seeding for our region’s water supply, which determined that it is feasible and cost-effective for our region. Following the study, SAWPA launched the Pilot Program on November 15, 2023, which will continue through April 2027 to demonstrate that cloud seeding works in our region. Once the four-year pilot program concludes, we’ll use the data to assess the precipitation benefits, while monitoring cost effectiveness, and decide whether or not the Pilot Program should be part of our region’s water management strategy in the future.
How does cloud seeding work?
You may be wondering how cloud seeding really works. The idea is to use particles, in this case silver iodide, to generate more precipitation in clouds so rain and snowfall increase by 5-15%. Here is a breakdown of the process:
1. Silver iodide particles mixed with acetone are vaporized and released into the atmosphere using ground-based seeding generators.
2. The silver iodide particles rise into cold, high-altitude air through storm wind currents near our mountain ranges. The moisture in the air condenses to form ice crystals around the particles.
3. As time passes, those ice crystals grow progressively larger, resulting in snowflakes large enough to fall to the ground in the form of additional precipitation. Pretty cool, right?
Is cloud seeding safe?
SAWPA’s Program was thoroughly studied through an environmental impact review process by the California Environmental Quality Act, otherwise known as CEQA. Also, the use of silver iodide for the purpose of seeding clouds has been shown to be safe for people and the environment, and it has been used for this purpose for decades. In over 50 years of experience, there have been no measurable human or environmental effects caused by silver iodide.
In fact, SAWPA’s CEQA Study shows that the amount of silver measured in the environment before and after cloud seeding events is not toxic to humans. The acetone is used to release the silver iodide particles into the air and is converted as part of this process into water and carbon dioxide. As a result, there is no human or environmental exposure to acetone during the operations. Silver iodide does not have a significant impact on human health or the environment at the low levels used as part of this initiative.
What are the benefits of cloud seeding?
Let’s talk about the good stuff. SAWPA is currently piloting and studying the water supply benefits of cloud seeding. It has the potential to:
- Increase precipitation by 5% to 15%, resulting in a greater streamflow in the Santa Ana River, which benefits river habitat.
- Increase the water supply for the region, enhance groundwater recharge, and reduce our reliance on imported water.
- Increase the snowpack for snow season recreational activities.
What time of year does cloud seeding take place?
Cloud seeding operations are conducted annually from November 15 to April 15 during winter storm season. Cloud seeding only takes place when storm clouds of specific weather conditions occur. Some factors taken into consideration are the type of storm, air temperatures in the clouds, meteorological conditions, and wind direction. Essentially, we are enhancing storms, not creating them.
Storms are monitored in real-time, and the decision to cloud seed depends on various factors including the size of the storm, the occurrence of sequential storms, the potential for flooding, the risk of debris flows, and the suspension criteria developed by SAWPA in collaboration with watershed stakeholders. As a result, not all storms are seeded during the operational period. SAWPA’s feasibility study suggested that based on storms from past years, about eight to 10 storms would be seeded during a winter storm season.
We hope this blog helped you understand a bit more about SAWPA’s Santa Ana River Weather Modification Pilot Program and the benefits it provides for our region.
To learn more, call our weather modification hotline at (951) 289-5440 or email SAWPA directly at weathermodification@sawpa.gov
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