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

Ecology teamed up with the United States Geological Survey (USGS) to evaluate nutrient contribution to Lake Spokane through groundwater from on-site septic systems. This study builds on a broader study conducted by Spokane County, which recommends further investigation of densely populated areas that rely on on-site septic systems for wastewater treatment. Data gathered will be used to evaluate if there is a nutrient contribution to the lake from areas with higher residential development compared to an area without homes.

More information about water quality monitoring on Lake Spokane at Suncrest

NPDES Permit Schedule

Ecology issued Washington municipal and industrial wastewater NPDES permits in November 2011, which began a ten-year compliance schedule for the Washington wastewater dischargers. Dischargers must meet certain milestones outlined by their compliance schedules and are working toward installing advanced treatment to reduce nutrients. By 2021, the wastewater dischargers will need to be in compliance with the nutrient limits established by the water quality improvement plan.

The Environmental Protection Agency issued permits for the Idaho wastewater dischargers in October 2014, which requires similar milestones and compliance.

Nonpoint Source

Local conservation districts and other organizations are continuing to work with landowners on reducing nonpoint sources by installing best management practices. Many incentive and cost-share programs are available to help off-set the cost for landowners to make needed improvements. These improvements are described in the Nonpoint Source Phosphorus Reduction Plan developed by Spokane County. The plan identifies types of best management practices and where they should be applied.

Local municipalities are also expected to help reach water quality goals through stormwater management. Municipal stormwater permits require the cities of Spokane and Spokane Valley along with Spokane County to reduce stormwater flows or eliminate stormwater outfalls to the river. The city of Spokane is also using their newly adopted Integrated Clean Water Plan to manage stormwater.

Avista Water Quality Attainment Plan

Avista identified actions in their Lake Spokane DO Water Quality Attainment Plan, to increase dissolved oxygen and reduce excess nutrients, which is available at their water quality website.

Other Plans

Both tributaries, Hangman Creek and the Little Spokane River have water quality improvement plans to reduce bacteria, temperature and turbidity. Actions and best management practices in these watersheds will also reduce the amount of nutrients entering the streams, river, and lake. Water quality improvement plan studies for dissolved oxygen and pH are in various stages of development for Hangman Creek and the Little Spokane River. Monitoring is underway on Coulee Creek and its tributary, Deep Creek, to gather information about nutrient sources.

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 April 2015
  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
Email: David.Knight@ecy.wa.gov

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