Waters of the State Definition Under California Law

In California, “waters of the state” means any surface water or groundwater, including saline waters, found within the state’s boundaries. That definition comes from Section 13050(e) of the California Water Code, and it is deliberately sweeping.¹ There is no size threshold, no requirement that water flow year-round, and no need for a connection to a navigable river or the ocean. If water sits on or beneath the ground inside California, the state has regulatory authority over it, and discharges that could affect it generally require a permit.

For anyone planning construction, grading, agricultural work, waste handling, or anything that moves fill or releases pollutants, this definition is the starting point for figuring out whether state water law applies to the project. In most cases, it does.

What the Definition Covers

The reach of Section 13050(e) is best understood by walking through the categories of water it captures.

Surface Water

Rivers, lakes, ponds, streams, and coastal waters all qualify regardless of size or remoteness. Saline inland bodies, including the Salton Sea, are included. The state does not require continuous flow: perennial streams, intermittent streams that dry up seasonally, and ephemeral channels that only carry water during and briefly after storms are all protected.²

In practical terms, a dry creek bed remains a regulated feature. Dumping fill or waste into a dry wash in Southern California or the Central Valley can draw the same enforcement response as discharging into a flowing river. The relevant question is whether the channel naturally carries water during storm events, not whether water happens to be present on the day of the work.

Groundwater

Every drop of water beneath the surface is included, from aquifers to the saturated zone where soils and rock are fully filled with water. Jurisdiction applies whether or not anyone is currently pumping that groundwater for drinking, irrigation, or industry.¹

This is where many landowners get caught off guard. Storing waste on bare ground, operating leaking underground tanks, or applying chemicals near a recharge area can create liability under state water law even when no visible water body is anywhere nearby. The discharge does not have to reach a stream to be regulated; reaching groundwater is enough.

Wetlands

In 2019, the State Water Resources Control Board adopted formal wetland identification procedures through Resolution No. 2019-0015.³ An area qualifies as a wetland if it meets three criteria:

Continuous or recurrent saturation of the upper soil layer caused by groundwater, shallow surface water, or both.
Saturation lasting long enough to create anaerobic (oxygen-depleted) conditions in that soil.
Dominance by plants adapted to wet conditions, or no vegetation at all.

That third point matters: a saturated, anaerobic area can be a regulated wetland even if nothing grows there.⁴ All natural wetlands count, along with wetlands created by modifying a surface water feature and certain artificial wetlands that have become relatively permanent or were approved as compensatory mitigation.

Artificial wetlands that are built and actively maintained for a specific purpose, such as wastewater treatment, stormwater management, crop irrigation, or industrial cooling, are generally excluded, unless they were designated in a water quality plan or approved as mitigation.⁴ Anyone proposing to discharge dredged or fill material into a state-regulated wetland must first try to avoid impacts, then minimize what cannot be avoided, and compensate for any remaining loss under a “no net loss” standard.

Man-Made Water Features

A feature is not exempt simply because someone built it. Canals, drainage ditches, reservoirs, and stock ponds can all fall within state jurisdiction.² The question is whether the feature has taken on the characteristics of a natural water body or replaced one. A drainage ditch that has existed long enough to support aquatic plants and wildlife may be regulated as a state water. A lined industrial containment pond that is isolated from surrounding hydrology and actively maintained for a specific purpose has a better case for exclusion, but the burden sits on the landowner to prove isolation. If the feature receives natural runoff, connects to groundwater, or has developed ecological function, expect the state to assert jurisdiction.

Why the State Definition Reaches Further Than Federal Law

California’s definition has always been broader than the federal “waters of the United States” standard under the Clean Water Act, and the gap widened in 2023. In Sackett v. EPA, the U.S. Supreme Court held that federal jurisdiction reaches only relatively permanent, standing, or continuously flowing waters with a continuous surface connection to navigable interstate waters. The Court rejected the earlier “significant nexus” test, which had extended federal protection to wetlands and water features with meaningful ecological connections to navigable waters even without a continuous surface link.

The State Water Board responded by noting that the ruling “only narrows the scope of federal jurisdiction” and “does not weaken California’s more stringent wetlands protections.”⁵ Under the Porter-Cologne Act, the state retains authority over roughly 1.6 million acres of lakes, 1.3 million acres of bays and estuaries, 211,000 miles of rivers and streams, and 1,100 miles of coastline. Isolated wetlands, ephemeral streams, and seasonal vernal pools that may no longer qualify for federal protection remain fully regulated as waters of the state.

The practical lesson: a determination from the U.S. Army Corps of Engineers that a site lacks federal jurisdiction does not relieve you of state obligations. Skipping state permits on the strength of a federal “no” is one of the more expensive mistakes a project proponent can make.

Who Regulates California’s Waters

Day-to-day regulation is handled by nine Regional Water Quality Control Boards, each covering a specific geographic basin.⁶ Each regional board adopts a Basin Plan that designates beneficial uses for the waters in its region (drinking supply, agricultural irrigation, fishing, recreation, wildlife habitat, and so on) and sets water quality objectives to protect those uses. Because objectives are tailored to local conditions, the same discharge may be allowed in one region and prohibited in another.

Separately, the California Department of Fish and Wildlife (CDFW) regulates physical alterations to rivers, streams, and lakes under Fish and Game Code Section 1602. Before you substantially divert or obstruct the natural flow, change the bed or bank, or deposit debris or waste material into any river, stream, or lake, you must notify CDFW in writing.⁷ This applies to features that are dry for parts of the year, not just those flowing year-round. If CDFW finds the activity will substantially alter the feature and may adversely affect fish or wildlife, you need a Lake and Streambed Alteration Agreement before work can begin. Emergency work to protect life or property can proceed first, but CDFW must be notified within 14 days.

What Triggers a Permit

If you discharge waste, or propose to discharge waste in a way that could affect any water of the state, you must file a Report of Waste Discharge with the appropriate regional board.⁸ The requirement is broad: it covers discharges to surface water, to groundwater, and to land where the discharge could eventually reach water. The regional board then issues Waste Discharge Requirements (WDRs) that operate as the project’s permit, specifying what may be discharged, in what quantities, and under what conditions.

When a discharge goes directly to surface waters that also qualify as waters of the United States, the WDRs double as a National Pollutant Discharge Elimination System (NPDES) permit under the Clean Water Act.⁹ For discharges that reach only state waters, the WDRs stand alone. Either way, operating without the required permit is a violation.

Timing

Plan ahead. NPDES permit applications must be filed at least 180 days before discharge begins, with review typically running six months or longer depending on complexity. WDR applications require at least 140 days of lead time, with the process typically taking about three months. Regional boards generally respond within 30 days to indicate whether an application is complete or deficient.¹⁰

Section 401 Certification

Projects that require a federal permit and may result in a discharge to waters of the United States also need a Section 401 Water Quality Certification from the state, confirming the project will meet state water quality standards. The certifying agency must act within a reasonable period not exceeding one year, and it can grant the certification, grant it with conditions, or deny it. Federal agencies cannot issue the underlying permit until the 401 process is complete.¹¹

Agricultural Waivers

Agricultural operations can sometimes avoid the full WDR process through conditional waivers. Under Water Code Section 13269, a regional board may waive the filing and permit requirements if doing so is consistent with the applicable water quality plan and serves the public interest. Waivers last no more than five years, can be renewed, and can be terminated at any time. Most require monitoring, individually or through a watershed-based program, to confirm the discharge is not degrading water quality.²

Penalties for Getting It Wrong

Enforcement is handled through administrative penalties, court actions, and cleanup orders, and the figures escalate quickly.

For violations of WDRs or NPDES permits, Section 13385 authorizes administrative penalties of up to $10,000 per day of violation, plus up to $10 per gallon for any discharge over 1,000 gallons that is not cleaned up. If the case moves to court, the ceiling rises to $25,000 per day and $25 per gallon. Serious violations carry a mandatory minimum penalty of $3,000 each.¹²

For unauthorized discharges and violations of cleanup orders, Section 13350 authorizes administrative penalties of up to $5,000 per day or $10 per gallon (the board picks one basis, not both). When a cleanup and abatement order is in place, the minimum is $500 per day for each day the discharge continues or the order is violated. Court-imposed penalties under this section can reach $15,000 per day or $20 per gallon.¹³

Beyond the penalty numbers, the regional boards can issue cleanup and abatement orders under Section 13304 against anyone who caused or allowed waste to be discharged where it has reached or will probably reach waters of the state. The responsible party bears the full cost of investigation and remediation, which for contaminated soil and groundwater routinely runs into millions of dollars over many years. In most enforcement actions, the cleanup liability ends up dwarfing the civil penalties themselves.

1
California Legislative Information. California Water Code 13050 (2025)
2
State Water Resources Control Board. Porter-Cologne Water Quality Control Act
3
Legal Information Institute. 23 CCR 2926 – State Policy for Water Quality Control: State Wetland Definition and Procedures for Discharges of Dredged or Fill Material to Waters of the State
4
State Water Resources Control Board. State Wetland Definition and Procedures for Discharges of Dredged or Fill Material to Waters of the State
5
State Water Resources Control Board. U.S. Supreme Court Decision Decreases Wetlands Protection
6
State Water Resources Control Board. The Nine Regional Water Quality Control Boards in California
7
California Department of Fish and Wildlife. Lake and Streambed Alteration Program
8
California Legislative Information. California Code, Water Code WAT 13260
9
State Water Resources Control Board. National Pollutant Discharge Elimination System (NPDES) – Wastewater
10
Central Valley Regional Water Quality Control Board. Do I Need a Permit?
11
U.S. Environmental Protection Agency. Overview of CWA Section 401 Certification
12
California Legislative Information. California Water Code 13385 (2025)
13
California Legislative Information. California Water Code 13350