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Water Quality Improvement Project
Spokane River and Lake Spokane Area:
Dissolved Oxygen

The Washington State Department of Ecology (Ecology) has worked in partnership with state, local and federal government, tribes, industry and the community to improve dissolved oxygen in the Spokane River and Lake Spokane since 1998.

Dissolved oxygen is important for fish, invertebrates and other aquatic life because they need oxygen to live. Excess nutrients like nitrogen and phosphorus in the Spokane River and Lake Spokane deplete dissolved oxygen and can also cause toxic algae blooms that are harmful to human and animal health.

Portions of the river and lake have excessive algae blooms during low flow in the summer months due to low dissolved oxygen and high phosphorus levels, which violate the Washington State water quality standards.

Washington State is required by the Clean Water Act to develop water a quality improvement plan because several segments of the river and lake were included on the state’s 1996, 1998 and 2004 303(d) lists of impaired water bodies.

Improving the river and lake

Reducing nutrients is key to improving dissolved oxygen levels and reducing algae blooms. Nutrients like phosphorus and nitrogen come from a variety of sources including wastewater treatment plants that discharge water into the river through a pipe. Discharges from pipes are called point sources. Ecology is working with point-source facilities along the river through the National Pollutant Discharge Elimination System (NPDES) permit process to upgrade treatment technology that will help meet water quality goals. The permits limit the amount of nutrients and outline other water quality requirements that point sources discharge into a body of water. NPDES-permitted facilities along the Spokane River in Washington include:

Spokane River Watershed.  Washington State Department of Ecology. The Spokane River flows from its source at Lake Coeur d’Alene in Idaho through the city of Spokane, Washington. It then flows northwesterly through Lake Spokane and the Spokane Tribe of Indian’s reservation on is path to Lake Roosevelt. The river drains an area of about 6,640 square miles in two states. Approximately 2,295 square miles are within Washington with the remainder of the watershed in Idaho.

There are three facilities in Idaho that discharge treated wastewater to the Spokane River.

Nonpoint sources are also a significant source of nutrients to the river and lake. These sources come from our activities on the landscape which enter surface water through runoff or groundwater. Nonpoint sources in the Spokane watershed include runoff containing fertilizer and pesticides from lawns and croplands, organic debris from forest land, soil erosion, faulty septic tanks, and stormwater. People can reduce nutrients from these sources by applying best management practices. Examples include vegetated buffers along waterways; keeping lawn clippings, manure, and livestock out of surface water; and allowing water from your property to soak into the ground rather than flowing onto streets or over the ground into ditches.

The 2010 Spokane River Dissolved Oxygen Total Maximum Daily Load report (TMDL) requires the following improvements over a ten year time period:

  • Remove more than 90 percent of total phosphorus from point sources in Washington.
  • Reduce up to half of nutrients from nonpoint sources in Hangman and Coulee creeks, the Little Spokane River, and surrounding Lake Spokane.
  • Improve dissolved oxygen conditions in Lake Spokane by Avista Utilities.

Status of actions to improve water quality

Ecology is working with wastewater dischargers, Avista, local conservation districts, environmental groups, and many others to implement the water quality improvement plan. Following is a description of some of the activities taking place to reduce nutrients in the river and lake. Another place to get information about what is happening with the TMDL project and work to reduce nutrients is the Spokane River Forum. The Forum’s purpose is to serve as a clearinghouse and information exchange for all Spokane River and Lake Spokane issues.

Water Quality Monitoring on Lake Spokane at Suncrest

NPDES Permit Schedule

Nonpoint Source

Avista Water Quality Attainment Plan

Other Plans

Monitoring Information

Monitoring data can be found in our Lake Spokane Nutrient Monitoring, 2010-2011: Data Summary Report. Wastewater dischargers and Avista are also required to monitor and report water quality information for the river.

More about dissolved oxygen in water

Modeling information

Related information


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Last updated May 2016
  Water resource inventory areas (WRIAs) 54-57 map, Washington State.


#54 (Lower Spokane)
#55 (Little Spokane)
#56 (Hangman)
#57 (Middle Spokane)

Pend Oreille

Water-body Names:
Spokane River
Lake Spokane

Dissolved Oxygen

# of TMDLs: 9


Contact Info:
David Knight
Phone: 509-329-3590

Eastern Region
Department of Ecology
4601 N Monroe St.
Spokane, WA 99205-1295