California Water Code: California Waters

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Learn everything you need to know about the California water code and how California defines different types of waters.

Why are Waters Defined Differently by State?

In the U.S., the Clean Water Act (CWA) protects waters. Jurisdictional Waters of the U.S. (WOTUS) are given extensive protection under this act. However, this act provides vague definitions for these waters, leading to the ambiguity of interpretations of these waters. States have added additional definitions to waters to gain clarity and protect waters that do not fall under the jurisdiction of the CWA as interpreted by different administrations.

Additionally, water use and needs vary by state—the different biogeographic regions in each state impact primary water sources and regulations are regionally specific. Protected waters house ecosystems that vary significantly by state. This variety of life and water use creates the need for state-specific regulations.

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California Water Code

The California Water Code outlines California Waters of the State. This act regulates the discharge of waste or fill into these waters. The defined waters of California include:

  • Any surface or groundwater (including saline waters) within the boundaries of the state

  • Various wetlands

  • All waters considered to be Waters of the United States (WOTUS)

Porter-Cologne Water Quality Control Act

The Porter-Cologne Water Quality Control Act is the state regulation that protects water quality for both surface water and groundwater- unlike the groundwater forward protection within federal laws. This act establishes regulatory power over California water for the California Water Board and the State Water Resources Control Board. The water agencies comply with federal regulations and establish complementing state water standards.

Sustainable Groundwater Management Act

California passed the Sustainable Groundwater Management Act (SGMA) in 2014, requiring local agencies to form groundwater sustainability agencies (GSAs). These local water agencies regulate high and medium groundwater basins by implementing groundwater sustainability plans (GSPs). These agencies serve a crucial role as California relies heavily on groundwater for its annual water supply, especially in a drought. These water management plans serve to protect and prevent water shortages in the state. Reductions in the quality or quantity of groundwater can yield significant impacts on Californians and their drinking water supply and the environment.

The California State Water Board

The State Water Board is a five-member board tasked with regulating statewide water regulations and supporting the efforts of the Regional Water Quality Control Boards. These boards regulate all the state's water resources and provide direction to ensure water quality is coherent with the guidelines provided within the Clean Water Act. The state and regional water quality control boards regulate nearly 211,000 miles of river and stream networks, 1.6 million acres of lakes, and extensive bays and coastlines. Managing water quality and regulating contaminants entering these waters is a key role of this board.

Regional Water Quality Control Boards

A California drought is not an uncommon occurrence, but each region in the state will face different water challenges. The nine regional water quality control boards regulate different biogeographic regions of California. The watersheds for these regions have diverse topography, climate, geology, and hydrology- presenting unique needs for each region. Water conservation needs may vary due to the difference in drought frequency between regions, impacting regional water use regulations. Higher-level boards uphold rules established at the regional level. These regulations develop both the regional water quality standard and enforcement actions.

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Free Permitting Checklist

Practical Tips to Avoid Environmental Risk on all Your Projects

Download our environmental permitting checklist to get a step-by-step list of ways to protect your project from the 9 most common environmental risks.

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California Wetlands

California wetlands are defined and regulated by the California State Water Board. The state-level further defines wetlands in addition to the definition provided in the Clean Water Act's description of Waters of the United States (WOTUS). The state-level provides additional wetlands definitions to accommodate the ambiguous and constantly changing federal definition.

California Wetlands Definition

California wetlands are defined as "An area is wetland if, under normal circumstances, (1) the area has continuous or recurrent saturation of the upper substrate caused by groundwater, or shallow surface water, or both; (2) the duration of such saturation is sufficient to cause anaerobic conditions in the upper substrate; and (3) the area's vegetation is dominated by hydrophytes or the area lacks vegetation."

Protection for Wetlands

State protections did not adopt California wetlands until 2019. Until this point, their protection was dependent upon the interpretation of the Waters of the United States (WOTUS). The Porter-Cologne Act, the current definition of WOTUS, and additional state and local restrictions protect wetlands in California. Waters not protected under provincial or federal regulations may qualify for protection under the internationally broad state definition of wetlands. Proper delineation and environmental due diligence will determine if water is a protected wetland and requires specific permitting or compliance steps.

California Streams

The drinking water for 7.3 million people in California originates from water systems fed by intermittent, ephemeral, or perennial streams. Of these stream networks, 66% are temporary streams. These streams play a vital role in the health of California waters and public health. Natural causes, such as wildfires and human interaction, impact California streams.

Protection for California Streams

The regulation for non-perennial streams falls under the jurisdiction of the California Water Boards. The California Water Code nor the 2020 Navigable Waters Protection Rule interpretation of Waters of the United States (WOTUS) did not initially protect non-perennial streams. This interpretation of WOTUS reduced protected California waters by 60-80%, a severe blow to the state's health. However, the increased belief in the importance of temporary streams has led to their further protection. The current California Water Code and interpretation of Waters of the United States as defined in the Clean Water Act protects all California streams. Though all streams are covered, California dedicates most stream research to perennial streams. As this research expands, California water regulations are likely to shift.

The Regional Water Quality Control Boards serve nine different subregions. Local levels may add additional regulations to suit the regions' specific needs:

  • The North Coast

  • The Chaparral along the Central Coast and foothills of the Central Valley 

  • The Sierra Nevada

  • The Central Valley floor

  • Southern California Coastal watersheds

  • The Desert-Modoc, which combines the Modoc Plateau and southern Desert areas

Most of the perennial streams in the state are in the North Coast and the Sierra Nevada regions. The arid areas and headwaters of the state's mountainous regions have stream networks comprised of mostly temporary streams. Due to these differences, regional regulations regarding streams and their adjacent wetlands and waters may vary.

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The Central Valley Project

The Central Valley Project is a federal project located in central California, covering the Sacramento-San Joaquin Delta and over 400 miles. This delta draws water from the Sacramento and San Joaquin rivers, serving as one of California’s most significant water sources and a water storage region to prevent flooding. This project is a system of dams, canals, hydroelectric power plants, reservoirs, and other facilities that began in Northern California and have continued to expand throughout the state. This water system is crucial for the water supply of the state and minimizing the possibility of a water shortage. This system is the urban water supply for areas such as the San Francisco Bay area. The state water board and federal laws regulate this water project. This network of waters serves as a habitat for many species protected by the Endangered Species Act (ESA) and protected by other federal infrastructure laws. CA water law will require additional regulations for project developments that will impact the quality of this water system.

How does California Water Law Impact Land Developers?

Protected California waters can delay a project timeline or result in expensive fines. Should there be a protected water feature on a project site, developers must take the proper permitting and mitigation steps for environmental compliance. These steps can take weeks to accomplish, and protected water features can deem a project site non-developable. Identifying environmental risks early during site selection can mitigate these setbacks or be largely avoided.

How to Find Protected California Waters on Your Project Site


Environmental Consultants

Environmental consultants are trained to survey sites for potential environmental impacts. The consultant can recommend necessary permits and steps to ensure environmental compliance if they find an environmental risk-such as protected water. This traditional process is completed manually by an environmental consultant over weeks or months.

Transect Protected Waters Map

Environmental due diligence software such as Transect uses machine learning to automate the mapping of protected waters. This software uses prior precipitation trends and current data about water locations to assess a specified region. The software provides the likelihood of regulated water appearing on a site and includes a corresponding confidence level. This mapping tool can select the right location for a project or discover a buildable area within a given plot. Transect will also provide a site-specific list of permits required to comply with federal, state, and local laws. Transect generates this report in minutes.

Transect Software helps land developers discover these waters on any given parcel of land.

To learn about more Environmental Regulations in California, check out the California section of our Environmental Regulations by State reference page.

Free Permitting Checklist

Practical Tips to Avoid Environmental Risk on all Your Projects

Download our environmental permitting checklist to get a step-by-step list of ways to protect your project from the 9 most common environmental risks.

Download Your Checklist