Water Quality Improvement Project
Lake Whatcom

Current Developments

Photo of Lake Whatcom On April 7, 2016, EPA approved a water quality improvement plan for Lake Whatcom. The plan, called the Lake Whatcom Watershed Total Phosphorus and Bacteria TMDL (total maximum daily load) addresses the lake’s decline in water quality which is attributed to an elevated amount of phosphorous, which causes excessive growth of algae blooms and low dissolved oxygen levels.

Ecology finalized and submitted the plan to EPA in November 2014.

The approved plan identifies the reductions in phosphorus and bacteria loading needed to restore the health of Lake Whatcom. It also establishes a link between increasing phosphorus levels and urban development.

The plan says that 87 percent of the developed area around the lake needs to store and filter water like a natural forest.

The requirements of the TMDL are now official. Implementation will be the responsibility of the city of Bellingham and Whatcom County.

Next steps:

  • A TMDL work plan, including a budget and timeline, is due to Ecology by October 7, 2016
  • In 2018, Ecology will issue the new municipal stormwater permits that will incorporate the targets set forth by the TMDL work plans.


Lake Whatcom is a large natural lake in Whatcom County. The northwest end of the lake lies within the city of Bellingham, and 22 small watersheds drain into the lake. Lake Whatcom serves as the drinking water source for about 96,000 people in the Bellingham area. The lake is popular for recreation, and the area around it has become a popular place to live.

Water quality issues

The lake has been threatened by declining water quality and in 1998 was put on the state’s list of polluted water bodies. The primary concern is low levels of dissolved oxygen as a result of increased levels of phosphorous and fecal coliform bacteria. A lack of oxygen threatens the survival of fish and aquatic plants. In addition, too much phosphorous can create an overgrowth of algae which can increase drinking water treatments costs and may require the use of more treatment chemicals.

Stormwater is the primary vehicle for phosphorous. Roofs, roads, driveways and lawns speed the flow of stormwater to the lake without the benefit of filtering out the phosphorous. In undeveloped areas, stormwater is allowed to slowly seep into the ground where it is filtered naturally before it reaches the lake.

The problems in Lake Whatcom triggered a water quality improvement project, the Lake Whatcom TMDL. From the beginning, the goal was to determine how much pollution the lake can process and still achieve acceptable levels of oxygen (See Study Area map).

Why this matters

Phosphorus is the main cause of Lake Whatcom’s low-oxygen problem. Phosphorus occurs naturally, but development increases phosphorus entering the lake in stormwater. Computer predictions show the lake would meet state standards for oxygen if there was 86 percent less development than existed in 2003. Since then, zoning laws have allowed more development in the watershed.

Sources: Runoff from bare soil and developed areas. Phosphorus occurs naturally in soil and human and animal waste, and is added to some detergents.

Connection to algae and oxygen: Phosphorus feeds algae growth. Bacteria that consume dying algae deplete the oxygen that fish and other aquatic life need to survive. When oxygen levels are low, phosphorus is released from lake sediment and re-enters the water, perpetuating the cycle. The dissolved oxygen levels in Lake Whatcom fail to meet state water quality standards now, and they have the potential to get much worse, making the problem much harder to fix.

Treatment of drinking water: Excess phosphorus creates larger algae blooms, which require more treatment to make the water safe for drinking. That process creates more trihalomethanes, a byproduct that some studies link to cancer.

Effect of development: Roofs, driveways and lawns interrupt the absorption and filtration provided by forests and soils, instead sending phosphorus-laden stormwater rushing to the lake. Communities must modify existing and future development to create the same effect as removing development.

Fecal coliform bacteria originate in human and animal waste. Runoff carries the bacteria from the ground and from failing septic systems into the lake. Eleven tributaries feeding Lake Whatcom fail to meet state standards for fecal coliform bacteria. The bacteria create a health risk for people who work or play in and around the water.

Technical information

Unless otherwise specified, the following documents are Ecology publications:

Lake Whatcom Watershed Total Phosphorus and Bacteria Total Maximum Daily Loads: Volume 2. Water Quality Improvement Report and Implementation Strategy

Lake Whatcom Watershed Total Phosphorus and Bacteria Total Maximum Daily Loads: Volume 1. Water Quality Study Findings

Dissolved Oxygen in Lake Whatcom/Trend in the Depletion of Hypolimnetic Oxygen in Basin I 83-97

Quality Assurance Project Plan: Lake Whatcom TMDL Study

Quality Assurance Project Plan: Characterization of Groundwater Discharge to Lake Whatcom

Lake Whatcom Total Maximum Daily Load Groundwater Study

Related information


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Last updated December 2015
  Water resource inventory area (WRIA) 1 map, Washington State.


WRIA(s): #1 (Nooksack)
County: Whatcom

Water-body Name:
Lake Whatcom

Fecal coliform bacteria

# of TMDLs: ---

Submitted to EPA for approval

Contact Info:
Steve Hood
Phone: 360-715-5211
Email: Steve.Hood@ecy.wa.gov

Bellingham Field Office
Department of Ecology
1440 - 10th St., Suite 102
Bellingham, WA 98225-7028