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.

A person in a blue shirt crouches next to a black water dispenser.

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

Yakima County GWMA webpage

Tracking nitrate levels in 170 wells

How to protect your well

Map of area with nitrate data — 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.

Person in an orange vest leans over a piece of white sampling equipment connected to a well. He is standing in grass near a white fence. — 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.

Yakima Health District is delivering free bottled water to people whose wells have high nitrate levels. It is also offering well testing resources like nitrate test strips and is working on community focus groups.
Contact: Shawn Magee or Jocelyn Castillo
Yakima County led planning efforts and continues supporting outreach and implementation.
Contact: Lisa Freund
Washington State Department of Health is funding the free bottled water delivered by the Yakima Health District. It completed an assessment of health risks from nitrate contamination in the Lower Yakima Valley. The agency also provides wellhead protection guidance.
Contact: Holly Myers or Sheryl Howe
South Yakima Conservation District coordinates implementation of the work plan and recommended actions developed by the advisory committee. The agency provides deep soil sampling and agricultural technical assistance for reducing nitrate levels.
Contact: Rodney Heit
Washington State Department of Agriculture studied sources of nitrate in the Lower Yakima Valley. The agency continues to provide agricultural technical assistance.
Contact: Gary Bahr

Learn more

Nitrate is the most mobile form of nitrogen, and it moves easily through soil with rain or irrigation.

When more nitrogen is added to the soil than crops can use, nitrate may leach to groundwater or run off into bodies of water. Using best practices to manage soil nitrogen can help prevent this and reduce impacts to groundwater quality.

Nitrogen can get into your water from:

Leaching — when nitrogen in soils moves below the root zone, traveling with water into groundwater
Runoff — when fields are frozen or oversaturated, nitrogen can move downhill toward drains, ditches, and water bodies
Decomposition — any dead organic matter left behind releases nitrogen into the soil.
Precipitation — small amounts of nitrogen are added to the soil from rain or snow
Fertilizer — applying manure, wastewater, or commercial fertilizers to crops adds nitrogen to soil

The graphic below shows how nitrogen moves through the environment.

Blue and green graphic showing how nitrogen moves through the environment — Click to enlarge the image.

Test your well water. Unlike public drinking water systems, you are responsible for maintaining and sampling your private domestic well. We recommend annual tests to ensure you know what's in your water and what you need to do to protect your health.

If your water doesn't meet drinking water standards, you can drink bottled water or get a water treatment system. You are not required to do anything if your water does not meet standards.

Keep chemicals and animals away from your wellhead. Contaminants can get into your drinking water from spills or leaks of pesticides, fertilizers, gasoline, and oil.

Check that your wellhead is protected. Ensure there is no corrosion compromising the well seal, which helps keep contaminants out of your drinking water.

Be mindful of what you do on your property. Many contaminants come from actions on the land nearby.

Maintain your septic system. Be mindful of chemicals you put down the drain.

Learn more about treating your well water from the Yakima Health District.

A labeled graphic showing how septic waste and above-ground contaminants can leach into groundwater — Septic tanks, pet and household waste, and fertilizers can all leach nitrates into groundwater — and your well — if not carefully managed.

The GWMA project is a community-based effort that requires collaboration between government agencies, local partners, and the Lower Yakima Valley community.

At the request of Yakima County, Ecology designated the GWMA and formed the Lower Yakima Valley GWMA Advisory Committee.

Over the course of six years, the committee developed a plan to reduce nitrate pollution from the many sources in the Lower Yakima Valley. The committee examined fertilizer, livestock, irrigation, and domestic, municipal, and commercial sources. As it built the plan, the committee conducted outreach to inform residents of the issue and gather feedback.

In 2019, the committee adopted recommendations to improve groundwater quality, and Ecology certified the plan. The project plan includes information about groundwater and land use in the GWMA, along with 64 recommended actions.

Now, alongside our GWMA project partners, we are focusing on implementing those recommended actions for clean, safe drinking water in the Lower Yakima Valley. Read more in the program documents section below.

Timeline: a history of the Lower Yakima Valley GWMA

Program certified

On June 20, 2019, the Lower Yakima Valley GWMA advisory committee approved the program by consensus and submitted it to Ecology for certification. On July 27, 2019, Ecology certified the program and is now working with an implementation committee to restart the effort after a delay due to the COVID-19 pandemic.

Ecology certification letter

Program documents:

Translated content

El Área de Manejo de Agua Subterránea del valle bajo de Yakima (GWMA) se formó en 2012 para abordar la meta de reducir la concentración de nitratos en el agua subterránea. El contenido del programa describe el problema de la elevación de los nitratos en el agua subterránea, cómo se estableció el programa GWMA en el valle bajo de Yakima y define las metas y objetivos desarrollados para el GWMA. Este informe explica los efectos ambientales y en la salud de los nitratos en el ambiente, describe los orígenes de nitrato, y las diferentes autoridades reguladoras que afectan el nitrato en el agua subterránea.

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We offer free language services about our programs and services for people whose primary language is not English. We can provide written information in your preferred language and interpreters in person or over the telephone.

Contact our Language Access team: civilrights@ecy.wa.gov

Contact information

Damon Roberts
Water Quality Regional Manager
damon.roberts@ecy.wa.gov
509-823-9626

Melanie Redding, LHG
Hydrogeologist
melanie.redding@ecy.wa.gov
509-309-5583

Media inquiries:

Emily Tasaka
Communications Manager
emily.tasaka@ecy.wa.gov
509-571-0352