Water availability

Each year, the state’s water supply is dependent on rainfall, snowpack, and temperature.  Surface and groundwater availability varies by watershed and the sub-basins within those watersheds. Water availability also depends on the water rights held by property owners in each area.

If you have questions about water availability for a particular property, you’ll want to start by knowing your watershed, also known as a Water Resource Inventory Area or WRIA. You might also want to know some basics about Washington water law so you better understand how decisions about water use allocations are made.

Statewide water conditions

Water availability is directly related to how much annual precipitation the state receives. We monitor current water and snowpack supplies and future weather conditions so we can inform the public and other agencies about trends and possible shortages. Read about current conditions around the state.

In partnership with USGS and others, we also monitor surface water levels around the state. Stream and river gauges are critical tools for maintaining instream flow levels, to support the health of fish populations, recreation, and aesthetics. View real-time data from our network of stream-gauging stations across the state.

Know your watershed

Washington has 62 major watersheds, which are areas defined by higher elevation that capture precipitation and funnel rain and snowmelt through smaller sub-basins into streams, tributaries, and rivers.

Due to Washington’s varied terrain and precipitation levels, water availability varies dramatically. To help study and manage watershed resources, we have divided the state into 62 Water Resource Inventory Areas (WRIAs).

Water availability is defined by water rights

While water may be physically present in a stream or well, it is only legally available if you have the right to use it.

Washington follows Western Water Law, which gives priority to those who first put a water source to a beneficial, continuous use. This approach is called “prior appropriation,” also known as “first-in-time, first-in-right,” which was codified by the Washington State Legislature in 1917. Learn more about Washington water rights on The history of water law page.

Diverting and using surface water — the freshwater from streams, lakes, or river sources — always requires a water right. In general, pumping groundwater from a well requires a water right permit unless it falls under the groundwater permit exemption, which limits most uses to less than 5,000 gallons per day.

Additional considerations

Early decades of water rights management focused on issuing and managing water rights and compliance. But as environmental scientists learned more about water’s limited availability, our work expanded to include the protection of the state’s water resources for the people, farms, and fish that depend on them.

As we look to the future, water availability studies include consideration of:

Is water available for my project?

Ultimately, water availability varies by sub-basins within a watershed. Some WRIAs receive less precipitation, have high water demand, and are very water-constrained. Certain areas have rules that require new uses of water be mitigated, or balanced, by returning an equal amount of water to the watershed.

A 2018 law impacts new residential permit-exempt wells in some rural parts of the state. The law lays out interim standards until local communities develop plans to invest in projects that help fish and streamflows.

Alternative water sources

When water right permits are not available for a new project, there are alternative sources of water to consider:

Water banks

Sometimes senior water rights holders find more efficient ways to use water to irrigate their fields, or may let some acreage go fallow. They may make excess water available to others through water banks, who act as brokers, water clearinghouses, and market-makers. Learn more about water banks.

Aquifer recharging

Storing water in underground aquifers is less expensive and safer than surface water reservoirs. Supplementing an aquifer’s water table by injecting or infusing water during times of abundant supply can increase water supply availability during seasonal low water periods. Learn more about aquifer storage, recovery, and recharge.

Rainwater collection

Using rain barrels and cisterns to collect rain water can add to both urban and rural water availability. Rainwater must be used on the property where it is collected, and it must be collected from existing, non-dedicated structures. Learn more about rainwater collection.

Reclaimed water

Reclaimed water is wastewater that has been cleaned and treated to remove nitrogen and pathogens so that it can be available for non-potable uses like crop irrigation, wetland enhancement, landscaping, and dust control. Read more about reclaimed water, including the reclaimed water rule