Dissolved Oxygen TMDL

Total Maximum Daily Loads (TMDLs), also known as water quality improvement projects, are required by the Clean Water Act (CWA) to return water bodies on the Water Quality Assessment 303[d] list to a healthy condition. TMDLs established today can also help manage water quality on a watershed scale to prevent the loss of beneficial uses in the future.

The Spokane River and Lake Spokane are listed on the 303[d] list for impairment of dissolved oxygen (DO). Modeling indicates that the main cause of the DO depletion is excess algae in the water bodies. The algae growth is primarily caused by excessive nutrients, with phosphorus being the growth limiting nutrient.

Spokane River Forum, DO TMDL Information


The Spokane River Forum is a non-profit organization that creates materials, events and activities that promote regional dialogues for sustaining a healthy river system while meeting the needs of a growing population. The purpose of the Spokane River Dissolved Oxygen TMDL Implementation Advisory Committee (Advisory Committee) is to enable Washington Department of Ecology (Ecology) to provide and receive feedback on implementation of the Spokane River DO TMDL.

Dissolved Oxygen Water Quality Improvement Project


The Spokane River Dissolved Oxygen Water Quality Improvement Project, Department of Ecology site provides information on the DO water quality improvement project for the Spokane River.

Nonpoint Source Phosphorus Assessment


Completed in 2011, the purpose of this study was to identify and evaluate existing scientific data to quantify nonpoint source (NPS) phosphorus loads in the Spokane River/Lake Spokane watershed. Where data was not available, the study determined possible data gaps and suggested studies for quantifying them.