Clean Water

Clean water is the lifeblood of the Estuary. Altered freshwater flow, excess nutrients, toxic contaminants, and high temperatures can harm aquatic life and make the Estuary unsafe for swimming and fishing.

American White Pelicans in the San Joaquin River Delta. Florence Low, California Department of Water Resources.

Good Water Quality is Essential for a Healthy Estuary

Water quality is the foundation of a healthy ecosystem in every part of the Estuary, from the smallest streams to the most expansive tidal marshes. Animals and plants that live in the water are highly sensitive to changes in salinity, water temperature, dissolved oxygen, and contaminants. Impacts on small organisms cascade up the food chain, disrupting aquatic and terrestrial habitats. Clean water is essential for Quality Habitat and Thriving Communities alike, ensuring that people and wildlife can thrive in the Estuary as they have for generations.

Indicators

Clean Water

Freshwater Flow

Measures the amounts, timing, and variability of fresh water flowing into the Estuary compared to the flows that would have occurred without dams and water diversions

Harmful Algal Blooms

Tracks indirect measures of harmful algae concentrations via measurements such as chlorophyll, toxin, and nutrient concentrations (Under development)

Safe for Aquatic Life

Assesses concentrations of toxic pollutants in water and fish from the Bay

Protecting Water Quality in a Changing Landscape

When clean water flows through the Estuary, it drives abundant sources of food and healthy habitats that allow wildlife populations to thrive. Vital habitats such as marshes, wetlands, and eelgrass beds rely on high-quality fresh and salty water. Low freshwater flow into the Estuary, limited by water diversions, dams, and other human uses upstream, threatens the balance of salt and nutrients.

Expanded research, monitoring, and real-time tracking of water quality and freshwater flows are pivotal for addressing current and emerging threats to the Estuary’s health. Upstream, restoration and pollution prevention are critical for ensuring clean freshwater continues to flow through the Estuary.

Clean Water for Future Generations

Clean water supports a healthy food chain, helping birds like this Black Oystercatcher access diverse intertidal prey and maintain healthy foraging habitat. Becky Matsubara, Flickr, CC BY 4.0 (2022).

Harmful algae blooms, driven by nutrient pollution, pose a threat to both humans and wildlife. An unprecedented bloom in the Bay in 2022 led to large fish die-offs. This image shows algae at Eden Landing in Hayward, CA. Joey Kotfica, Metropolitan Transportation Commission (2024).

Mussels and other shellfish are important indicators of estuary health. Because these species are prone to accumulating harmful levels of algal toxins, they must be closely monitored to protect the health of the Estuary and its residents. Kelly M. Grow, California Department of Water Resources (2020).

Nine of the ten largest Sacramento-San Joaquin watershed tributaries to the Estuary are dammed and managed for flood control and water supply. In this image, freshwater flows through the Oroville Dam, eventually making its way to the Sacramento River. Ken James, California Department of Water Resources (2023).

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