Skip to main content

COVID-19 Updates: Get the latest public information related to coronavirus disease 2019 (COVID-19) at

Public Works will re-open our front counter to the public on July 6 and start providing some modified services.  Our hours will be 8 – 5, with closure from 12 – 1:30 for sanitation. Masks are mandatory in our building, and we ask that you adhere to physical distancing protocol. We will have limited services at our front counter and will not be accepting drop in meetings.  Please contact 805-781-5252 to make an appointment with staff.  Bus passes can be purchased at the Kiosk on the corner of Osos and Palm or by phone via Follow us on Twitter @SLOCountyPWD for the latest updates.

Return to the top of the page

Winter Cloud Seeding Program for Lopez Lake

Project Contacts

For more information please contact Jill Ogren via email.

Frequently Asked Questions

What is Cloud seeding?

To put it simply, cloud seeding is a process that takes advantage of weather conditions to increase the amount of rainfall produced from clouds.

How does cloud seeding work?

Cloud seeding helps clouds produce more rain by adding tiny particles to the clouds. Inside the seeded clouds, water vapor freezes onto the particles making the vapor heavier. These heavier frozen particles then fall towards the ground as rain. Cloud seeding does not create new clouds; it increases the amount of rainfall from existing clouds. Cloud seeding typically helps existing clouds produce 10-15% more rainfall than if the clouds were not seeded.

Is cloud seeding safe?

A proposed project does not present a significant safety risk and is not expected to conflict with any regional emergency response or evacuation plan. Other counties, including Los Angeles County and Santa Barbara County, use cloud seeding to enhance their water supply. The County conducted an Environmental Study to identify and minimize any risks.

Does the County currently have a cloud seeding program?

Yes, on December 17th 2019 the BOS approved a program for the Lopez Reservoir Watershed.  The program is set for January 8, 2020 to April 15th 2020 and tentatively set for Nov 15 2020 thru April 15 2021 and Nov 15 2021 thru April 15 2022.  The project objective is to enhance rainfall in the upper watershed of Lopez Reservoir. The seeding program would use a combination of seeding by aircraft and land sites. It has been estimated that precipitation increases would be between 9% and 17% in the reservoir watershed area.

Does cloud seeding harm the environment?

There is no evidence that suggests cloud seeding creates any significant negative environmental impacts. To understand how any potential risks can be minimized, review the Environmental Study released by the County in February 2018.

What materials are used in cloud seeding?

The most common material in cloud seeding is silver iodide.

Contact Public Works via web form, email, or call us at (805) 781-5252.