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Watsonville Slough System Water Quality Report Card

Drag the image slider to see water quality conditions over time.
  • About

    Given the importance of the Watsonville Slough System and the many past and present impacts, many local and regional partners are dedicating significant time and effort to improving the water quality of the slough system.  This includes local government, non-governmental and special district agencies, public and private landowners, local growers and Pajaro Valley residents.

    In support of this effort, Watsonville Wetlands Watch volunteers sample water quality throughout the slough system.  This work is coordinated and conducted in partnership with the City of Watsonville and County of Santa Cruz who run the samples and also greatly support the community science water quality monitoring program with technical expertise and laboratory analysis.

  • WQI scores over time

    Play the video to see the chagnes over time.

  • Project Tierra

    Project Tierra is a community-science program that engages students and community volunteers in collecting and recording environmental science data in order to monitor the overall biodiversity and health of the Watsonville wetlands.

    While the program’s environmental focus produces data for the students as well as the larger scientific community on water quality and on plant and bird populations, the field-based research also increases the community’s understanding of the importance of biodiversity, sustainable land management practices, and environmental stewardship.

    Contact Cara Clark for more more information.

  • How To Help

    If you would like to volunteer to sample water quality with Watsonville Wetlands Watch and volunteer to restore local wetland habitats, please visit our volunteer opportunities page or call us at the Fitz Wetlands Educational Resource Center located at the top of Pajaro Valley High School, or call us at 831-728-1156.

    View Volunteer Opportunities

Assessing the Water Quality Score

In order to provide an assessment of the health of the wetlands, we use a Water Quality Index Score for each sampling location. The assessment method was developed by the Canadian Council of Environmental Ministries and is used throughout North America as a way to assess the health of wetlands. Sampling parameters include temperature, dissolved oxygen, pH nitrates, phosphates, and turbidity (murkiness of the water).

A score is assigned to each sampling location based on the levels of these monitoring parameters that are healthy for wetlands. We then look at the Water Quality Index scores over time at each sampling location to understand the health of the wetlands and how it changes over time. This is used to guide management of the wetlands and environmental restoration efforts to improve water quality and wetland health.

What Can We Do to Improve Water Quality in Our Wetlands?

Over 70% of the streets in the City of Watsonville drain directly and untreated to the surrounding wetlands. Due to ongoing and historic water quality impairment, the wetlands are listed as impaired by the California Water Quality Control Board. The good news is that every day actions can help to improve the water quality in our wetlands. Every action, small or large, makes a difference!

Ways We Can Help to Improve Water Quality and Wetland Health:

  1. Limit use of fertilizers and pesticides in areas where runoff will end up in the wetlands.
  2. Pick up and bag all dog poop on the trails and in areas where it will drain to wetlands and contribute to bacteria increases in the wetlands.
  3. Use established car wash locations rather than your yard, where soap can drain to the wetlands.
  4. Restore native habitat and plant trees in your front yard! For free trees go to To learn more about the City of Watsonville’s rebate programs for water conservation go to:
  5. Don’t dump or litter and pick up trash when you see it to keep it out of our wetlands and waterways.
  6. Contribute to habitat restoration efforts by volunteering with Watsonville Wetlands Watch.
  7. Volunteer to clean up wetlands and sample water quality!

About Project Tierra and the Watsonville Slough System Water Quality Report Card

Project Tierra is a community science monitoring program for the wetlands in Watsonville. Volunteers and local students conduct regular monitoring to help understand wetland and environmental health. They monitor water quality, bird populations, aquatic invertebrates, and native plants. Water quality sampling data was compiled by Watsonville Wetlands Watch. Water quality samples were analyzed by the City of Watsonville and County of Santa Cruz, who have been instrumental in enabling the ongoing sampling of water quality in the slough system. Funding for Project Tierra and this report card comes from the Resources Legacy Fund and other private foundations that support Watsonville Wetlands Watch’s education and volunteer programs.

A Water Quality Report Card for the Watsonville Slough System

The Watsonville Slough System is an 800 acre wetland system that underlies the City of Watsonville and surrounding areas. This wetland system is one of the largest remaining wetlands on the California Coast. The diverse habitat areas of the wetlands support over 270 resident and migratory bird species and 23 native plants and animals that are State and federally listed as threatened, endangered, and species of special concern. The wetlands support flood control for City residents and surrounding farms, buffer the community from the impacts associated with sea level rise, are a sponge for atmospheric carbon to reduce the effects of climate change, naturally filter the water draining to the Monterey Bay, and provide a place for residents and visitors to enjoy nature and walk on the City’s nine miles of recreational trails and greenbelt.

Water Quality Monitoring

Monitoring of the environmental health of the water in the wetlands provides us with a snapshot of their health. This helps us to answer the question, “How healthy are our wetlands?” and to understand how water quality changes over time. Every one to two months, volunteers from Watsonville Wetlands Watch’s Project Tierra Community Science Monitoring Program sample water throughout the wetlands. Water sampling is also done on the ‘First Flush,’ which occurs after the first large rain of each year (typically in October or November), and on Snapshot Day, an annual water quality monitoring data collection coordinated throughout the Monterey Bay National Marine Sanctuary.

You Can Help!

If you would like to volunteer to sample water quality with Watsonville Wetlands Watch and volunteer to restore local wetland habitats, please visit our volunteer opportunities page or call us at the Fitz Wetlands Educational Resource Center located at the top of Pajaro Valley High School, or call us at 831-728-1156.