Water quality improvement

We work to protect the quality of Washington's marine and fresh waters for the benefit of people and wildlife. We evaluate whether state water quality standards are being met. We also partner with stakeholders to improve water quality where problems are identified.

Managing water quality

We conduct a yearly planning process to determine and prioritize which water quality improvement projects are most needed for that year.

A water quality improvement project:

  • Assesses pollution levels and pollution sources in the project area.
  • Sets out actions needed to reduce and clean up local waters so that they meet water quality standards.

Our goal is to make measurable improvements in water quality by:

  • Issuing discharge permits to address point source pollution.
  • Implementing best management practices (BMPs) that prevent runoff pollution.
  • Educating the public.
  • Partnering with local governments and businesses.

Water quality improvement process

Data collection

The process starts with collecting data on water bodies across the state. Our scientists, as well as dozens of other organizations, collect high quality data that can be used to assess the status of water quality in streams, lakes, and marine waters throughout Washington.

Even though a vast amount of data is collected, we often only have a limited amount of data for any given pollutant in any individual waterbody.

Data assessment

We evaluate the data and information we receive against the water quality standards. The water bodies are placed into categories based on their water quality status. We then provide a water quality assessment report that groups waters into categories that describe the status of their quality.

The waterbodies in this assessment that do not meet water quality standards are considered to have impaired designated uses and are placed on Washington’s 303(d) list. We then use the 303(d) list to determine where local pollution levels are high and where to start new water quality improvement projects.

Getting to clean water

Once the project areas are selected, we choose a project process:

  • Total Maximum Daily Load (TMDL)
    The TMDL process cleans up polluted water so that it meets state water quality standards.
  • Straight to Implementation
    Straight to implementation allows us to clean up a watershed without having to use a TMDL process. Straight to implementation can be useful for cleaning up waters when we already know what the pollutant sources are in a water body and what we need to do about them.
  • Complex pollution projects
    These projects may include concurrent pollution impacts on land, water, and other issues. We participate in these multiple-issue projects, when needed, to determine the best way to protect water quality within the project scope.


Once the pollution problem and the pollution sources are determined, we write a water quality improvement plan. We work with local governments, communities, and other interested groups in the watershed to implement it.

Find TMDL projects in your county

Funding opportunities

Sometimes implementing BMPs and the steps to improve water quality can be costly. We and the Environmental Protection Agency (EPA) can provide grant money to communities and landowners to help them integrate BMPs that prevent or capture pollution. Find out more about funding that is available.

Monitoring progress

At certain points in the cleanup process, we monitor the project water body to check its progress in getting to clean water.

Effectiveness monitoring shows us how well the health of the water body is improving. We use the results to refine BMPs, identify additional pollutant sources, and compare existing water quality to the desired water quality goal.

Arriving at the goal — clean water

When monitoring shows that the water body is meeting state water quality standards, the status of the water body is changed to Category 1 in the state’s water quality assessment. This means it meets tested standards for clean water. The water body will continue to be monitored occasionally to insure that it continues to meet state standards.

Getting involved

Everyone plays a role in reducing pollution to protect and preserve the quality of the state's waters. Partnerships are one of the most productive ways to protect water quality. Find out more by visiting Washington Waters — Ours to Protect.