Lower Yakima Valley Groundwater Management Area

We're working with local and state partners to reduce nitrate contamination in groundwater in the Lower Yakima Valley. Many people in this area use groundwater wells for drinking and cooking at home.

This community-wide project aims to reduce sources of nitrates, improve the aquifer so it meets drinking water standards, and educate residents about the problem and how they can protect themselves. We are using a long-term, holistic approach to address this issue because nitrates come from many sources.

We provide ongoing technical assistance, well monitoring, and education and outreach support to our partner agencies in the groundwater management group. More information is available on the Yakima County website.

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What's happening now?

We are working with state and local agencies to address the problem, including implementing 64 recommended actions developed by an advisory committee.

We are currently monitoring nitrate levels in 170 wells throughout the area. Our data tell us how nitrate levels change across the area and how results may depend on seasonal variability or the conditions of a particular well. This helps us evaluate the success of our efforts to reduce nitrate pollution.

Read our newsletter with the latest updates on this project.

Free bottled water

With support from Ecology, the Yakima Health District and state Department of Health are delivering free bottled water to residents whose wells have high nitrate levels. Cleaning up groundwater takes time, so in the short term we want to make sure everyone in the Groundwater Management Area has clean, safe drinking water.


Quick links

In blue: the portion of the Lower Yakima Valley formally included in this project. This area is known as the Groundwater Management Area. Click to enlarge the map.


What is the GWMA?

The Lower Yakima Valley Groundwater Management Area (GWMA) is the area where we are working to reduce nitrate contamination in groundwater. The GWMA covers much of the Lower Yakima Valley watershed. Its designation helps focus resources on an area that provides drinking water for about 56,000 people.

Why are nitrates a concern?

Nitrate is a chemical that can come from human waste, animal waste, fertilizer, commercial activities, and even natural sources. It is the most common groundwater contaminant and can easily move through soil with rain or irrigation.

Our data estimates that 21% of wells in the Lower Yakima Valley may have elevated levels of nitrate. This can pose health risks to vulnerable populations like infants, pregnant people, and people with certain health conditions.

Learn more about the health impacts of nitrate from the Yakima Health District and Department of Health.

Ecology staff collecting a sample from a residential drinking water well to test for nitrates. This is part of a project to regularly sample 170 wells throughout the GWMA.

Working together for clean drinking water

We are working with county, local health, state, federal, and agricultural partners. These groups participate in a committee tasked with implementing the approved plan to reduce nitrate concentrations. Learn more in the program documents section below.

Our staff continue to lend support through community outreach, research, data collection, and technical expertise to make this effort a success.

Our partners

Many agencies and organizations are working to help people safely use groundwater in the Lower Yakima Valley.

Learn more

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