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Participate in the Cal-WATCH Study

Testing drinking water from wells, intakes, and creeks

Over 60% of Lake County residents receive their drinking water from Clear Lake. For those not using a public water system for household water, testing for contaminants such as cyanotoxins from HABs, nitrates, coliform bacteria, and herbicides is not regularly done.

In this study, our goals are to:

  • Understand whether there are contaminants that may pose a health risk to those drawing water from untreated and untested lake intakes or wells
  • Understand whether similar contaminants may pose a health risk to those who live alongside and draw water from creeks in Lake County
  • Educate residents on potential health risks from untested drinking water
  • Offer a one-time test for contaminants of at-risk wells and lake water intakes

Interested in having your drinking water tested?

To see if you qualify, please complete a short online form by clicking on the link below. A researcher will follow up with you regardless of whether or not you are eligible to participate.

This year, we will also be testing homes alongside creeks in Lake County that do not receive their drinking water from a public water system. To see if you are eligible to have your water tested, please click on the link below.

Complete our screening form

If you are a resident of a home with a well or intake, check out our Cal-WATCH Resources page.

Have you visited Clear Lake in the last week, month, or year? We'd like to know.

We are interested in hearing about what you know about Harmful Algal Blooms and whether or not you may have come in contact with them while visiting beaches/shorelines along Clear Lake or creeks in Lake County. Our survey was developed by state and local agencies and Lake County Tribes to better understand how people and pets encounter and avoid harmful algal blooms (HABs).

This survey is currently closed; however, please contact us if you'd like additional information.

Learn about potential well water contaminants and their impacts

Private wells can be contaminated by naturally occurring sources and human activities as seen in this diagram. To learn more about these potential contaminants and their impacts, click here.

Diagram of how water reaches wells

Source: EPA Potential Well Water Contaminants and their Impacts

There are also measures you can take to protect your health today. Find out if your water is safe to cook and drink. Note that boiling water will not remove algal toxins. When in doubt, use store bought water.

HABs and drinking water contaminants are difficult and expensive to eliminate, but exposures can be prevented through public education in impacted areas. There are measures you can take to protect your health:

If you suspect a bloom or would like to file a report, please call 1-844-729-6466, email, or submit a form at

Additional information on HABs, cyanotoxins, blue-green algae:
Big Valley Band of Pomo Indians Clear Lake Cyanotoxins
Cyanobacteria in Lake County
Freshwater CyanoHABs Program (State Water Resources Control Board)
Office of Environmental Health Hazard Assessment Harmful Algal Blooms
Tracking California Harmful Algal Blooms

Learn more about the CalWATCH project

The Cal-WATCH project (1 NUE1EH001427-01-00) is supported by the Centers for Disease Control and Prevention of the U.S. Department of Health and Human Services (HHS) as part of a financial assistance award totaling $290,000 in year 1, with 100 percent funded by CDC/HHS. The contents are those of the author(s) and do not necessarily represent the official views of, nor an endorsement, by CDC/HHS, or the U.S. Government.