French and Pilchuck watersheds

Water quality issues

Although we think water temperatures are good in the French Creek watershed for most of the year, high water temperatures occur during the warm weather months. 

French Creek is considered core summer salmonid habitat. This means its waters are expected to remain cool (below 16°C or 60.8°F) for optimal conditions. Maintaining cooler water temperatures helps improve habitat for fish and other aquatic life.

What we have done

We originally began a combined temperature and dissolved oxygen (DO) total maximum daily load (TMDL) project for the French Creek and Pilchuck River watersheds in 2012. During the initial phases of the project, we worked with the EPA and a scientific consulting firm to design the study. During the summer of 2012, we conducted extensive field studies.

As part of the 2013 data assessment, we determined that we could not use some of the data collected in lower French Creek because stream flows were extremely low. When looking at our Pilchuck River data, we determined that additional flow and groundwater data was needed. We collected that data during the summers of 2014 and 2016.

We separated the French Creek project from the Pilchuck

In fall of 2016, we separated the Pilchuck River Temperature/DO TMDL from the French Creek Temperature/DO TMDL to speed delivery of useful information to salmon recovery specialists working in that watershed. We also decided to conduct additional modeling and analysis for the Pilchuck River TMDL. This helped ensure that work would provide the broadest and most meaningful implementation actions to benefit salmon recovery.

We were able to complete the Pilchuck River Dissolved Oxygen and Temperature Total Maximum Daily Load (TMDL) water quality improvement plan in 2020 and EPA approved the TMDL in early 2021. French Creek water cleanup project work is still ongoing.

We completed modeling for the French Creek temperature project in 2024 and are developing a draft modeling report. The temperature modeling report will inform the next steps of the French Creek water cleanup project, including actions needed in the implementation plan to get to clean water.  We will have a presentation on the modeling report in late Fall/early Winter 2025. The implementation plan will highlight the benefits of recomended actions, such as planting trees, along with a plan for improving water quality. We will hold a kick-off meeting in early 2026 with local interested parties including the French Slough Flood Control District. During this meeting, we plan to explain our preliminary findings and work with partners to develop the implementation plan for improving water quality.
 

Why this matters

Oxygen dissolved in water is vital for fish and aquatic life to "breathe” to survive. It is more difficult to transfer oxygen from water to blood than it is to transfer oxygen from air to blood. Therefore, it is critical that an adequate amount of oxygen is maintained in the water for this transfer to take place efficiently and to sustain aquatic life. Oxygen is also necessary to help decompose organic matter in the water and bottom sediments as well as for other biological and chemical processes.

Water temperature influences what types of organisms can live in a water body. Cooler water can hold more dissolved oxygen that fish and other aquatic life need to breathe. Warmer water holds less dissolved oxygen. Many fish need cold, clean water to survive.

Each water body has unique characteristics and influence. For example, water quality and fish passage in French Creek are significantly affected by the French Slough pump station and numerous changes to the watershed in the floodplain area. There were structural changes on the lower reaches of the Pilchuck River.  The middle and lower sections of the river are also affected by summer irrigation withdrawals and municipal wastewater discharges from the city of Granite Falls.