Water availability

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.

We rely on a variety of data sources to evaluate the state's current and future water supply. You can see links to streamflow, snowpack, precipitation, groundwater, drought monitoring, climate forecasts and agricultural reservoirs on our Water supply monitoring page.

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

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 the following:

• Research establishing the continuity of ground and surface waters. 
• Instream flow rules granting water rights to surface waters to protect instream resources including fish, navigation, and aesthetics.
• Climate changes and warmer temperatures that affect precipitation, streamflows, and snowpack.

Due to Washington’s varied land uses, hydrology, and precipitation levels, the amount of water available for new water right permits varies dramatically across the state. 

Learn more about watersheds and WRIAs including our new water availability focus sheets.

History of water rights

Washington follows Western Water Law, which gives priority to those who first put a water source to a beneficial, ongoing, and consistent use. This approach is called “prior appropriation,” also known as “first-in-time, first-in-right,” which was codified by the Washington Legislature in 1917.

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.

• Learn more or check to see if you’re affected

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.