Cloud Seeding
Cloud Seeding
Turlock Irrigation District employs a program known as “cloud seeding,” which works to augment natural precipitation to increase surface water runoff in the Tuolumne River Watershed. Cloud seeding is a scientific technique used to boost a cloud’s capacity to generate precipitation. The process is performed by igniting flares emitting silver-iodide particles which act as nuclei for water molecules to bond with, create ice crystals and fall to the Earth’s surface as precipitation in the form of rain or snow.
Cloud Seeding Process
While cloud seeding has been active in California since the 1950s, TID began their cloud seeding program in 1990. When cloud seeding, water crystals form on microscopic ice nuclei, which are extremely small particles of dust or dirt in the atmosphere. Cloud seeding injects artificial glaciogenic material into the convective bands and cloud mass, providing a mechanism to move the moisture from the cloud mass to the surface of the earth where it is needed.
Cloud seeding is performed November through April, during dry and average water years, when the optimal conditions in naturally occurring storms are present. When natural storm conditions are present, the plane is flown into the storm to test for cloud seeding potential and if conditions are met, the operation will take place. The program may change each year to reflect watershed and hydrologic conditions. Additionally, program suspension criteria are in place to prevent flights based on storm severity and to avoid contributing to naturally occurring hazardous situations such as rain fall over burn scared areas with erosion potential, atmospheric rivers, etc.
Safe & Effective
The practice of cloud seeding in the Tuolumne River Watershed has proven to be a cost-effective and positive addition to water resources management goals and objectives. TID and MID participate in cloud seeding to assist naturally occurring storm events to increase precipitation production, predominantly in the form of snowfall, to help increase available annual water supplies for agricultural production, environmental needs and to generate carbon-free energy for the region. Analysis has shown a potential increase of 5-15% in precipitation volumes.
Cloud seeding programs are conducted throughout California and are common throughout the world. The California Department of Water Resources labels cloud seeding a “safe and effective means of augmenting local water supplies” and outlines the benefits of precipitation enhancement in the Resources Management Strategies of the California Water Plan.
Prior to implementing the program, the TID/MID program had to be evaluated by a strenuous California Environmental Quality Act (CEQA) process and was approved. Multiple studies on cloud-seeding conducted by the US Bureau of Reclamation, the California Department of Water Resources, North Dakota Atmospheric Resource Board, North American Weather Modification Council, and others, have determined that cloud-seeding does not negatively impact humans, animals or plants.
Silver and silver compounds have a low order of toxicity. Silver concentrations in surface water runoff have been measured from both seeded and unseeded watersheds. While a range of results has been recorded for both circumstances, available data suggest that silver in seeded waters occurs within the same concentration range as silver in unseeded surface water.
The American Society of Civil Engineers (ASCE) recognizes cloud seeding and has produced an operations guidelines manual. The Weather Modification Association and the North American Weather Modification Council provide excellent information on international programs, studies, methodology, and seeding material. Turlock Irrigation District’s program is in compliance with the California Environmental Quality Act and conducted in accordance with all applicable laws and licensing.
As studies have shown no negative impacts caused by cloud-seeding, and given that the program has been shown to increase snowpack in seeded areas, creating more runoff and surface water that can be put to beneficial use for irrigation, clean hydropower generation and environmental needs, TID and MID will continue to operate a cloud-seeding program when the correct weather conditions are present. Our program includes continuous monitoring and reporting, to confirm that we continue to see benefit from the program.
Contact
If you have any questions regarding the Cloud Seeding Program, please contact Turlock Irrigation District at (209) 883-8222.