Water Quality Improvement Project
Lake Chelan Area:


Lake Chelan is located in north-central Washington State. It is the longest and deepest natural lake in the state. Lake Chelan collects water from a watershed that is 924-square-miles. Ninety percent of the watershed is forested or open lands, with the majority managed by the United States Department of Agriculture’s Forest Service (USFS) and the National Park Service. The lake itself occupies two distinct basins: the northwestern Lucerne Basin and the southeastern Wapato Basin. Lands used for agriculture and orchards comprise three percent of the watershed’s land area, almost all located in the more developed area surrounding the Wapato Basin. A cluster of three small lakes: Roses Lake, Wapato Lake and Dry Lake, are located about a mile north of the town of Manson and drain to Lake Chelan.

Water quality issues

Persistent, man-made chemicals, a legacy of past agricultural and industrial activities, contaminate the sediment, water and fishes in Lake Chelan and Roses Lake. These toxins are the pesticide DDT and its associated breakdown products, as well as polychlorinated biphenyls (PCBs). Federal and state governments banned the use of these toxins more than 25 years ago, but they still persist in water, land and fish in the Lake Chelan watershed today. The improvement of Lake Chelan’s sediment, water quality and fish will depend on minimizing the movement of these contaminants from the surrounding lands to the lake and its tributaries. This Water Quality Implementation Plan addresses 303(d) listings for DDT and PCBs in fish tissue in Lake Chelan and Roses Lake.

DDT and PCB compounds enter Lake Chelan and Roses Lake and accumulate in the tissues of the fish living in these waters. The levels of these chemicals in the tissue of burbot, kokanee and lake trout exceed federal and state water quality standards set to protect human health. The state of Washington completed a Water Quality Improvement Report (WQIR), also known as a Total Maximum Daily Load (TMDL), to address these contaminants in the fish of Lake Chelan and Roses Lake.

Why this matters

Dichloro-Diphenyl-Trichloroethane (DDT) is a colorless, odorless, chlorinated insecticide that is water resistant. It tends to accumulate in sediment, plants, aquatic plants and animals, and fish. DDT is regularly found in waters near fruit orchards. It was widely used from the mid-1940s until 1958, when the U.S. Department of Agriculture (USDA) began a program to phase it out for its insect control programs due to concerns about its persistence in the environment and toxicity to non-target organisms, such as aquatic life. In 1972, the U.S. Environmental Protection Agency (EPA) banned DDT for all uses except for emergencies.

Despite the ban, DDT persists in the environment. Soils containing DDT can end up in streams and other surface water bodies through erosion. As DDT is transported to streams, it is absorbed by the plant and animal life within the stream system and then moves up the food chain. DDT biomagnifies at higher levels in each step of the food chain (plants, aquatic biota, fish, humans). DDT can also be found in ground water, as water infiltrates through contaminated soils into aquifers.

Pesticides and polychlorinated biphenyls (PCBs) can be toxic to fish and wildlife that use a contaminated water body.

In the past, PCBs were used as coolants and lubricants in electrical equipment such as transformers and capacitors. The United States banned the manufacture of PCBs in 1977 because they build up in the environment and can be harmful to humans and wildlife. PCB exposure can occur if you:

  • Eat food, including fish, meat, and dairy products that is contaminated by PCBs.
  • Drink PCB-contaminated water.
  • Breathe air near hazardous waste sites that contain PCBs.

Phosphorus fuels the growth of algae. When algae die, they remove oxygen from the water. Fish and aquatic life need oxygen to survive.

Status of the project

Residues of DDT persist in soils where it was applied, most often on agricultural lands. These residues move with soils when erosion occurs. DDT can also move through the soil profile to ground water during irrigation, snowmelt, and rain events. The most practical means to minimize the additions of DDT to the lake are taking steps to minimize (1) soil erosion to surface water and (2) DDT transport through the soil profile to ground water from the agricultural lands.

Many actions were taken to reduce the input of DDT and PCB contamination in the environment. DDT and PCBs were both banned in 1970s, which established the beginning of environmental recovery. Reduced soil erosion and improved management of riparian lands also contributed to the reduction of DDT in the Lake Chelan watershed. Regulatory restrictions, as well as collection and disposal of old PCB electrical equipment, reduced the quantity of PCBs entering the environment.

Additionally, the Lake Chelan Watershed DDT and PCB TMDL Water Quality Improvement Report identified several actions to reduce inputs of these legacy pollutants to Lake Chelan and Roses Lake. Water quality standards for DDT and PCBs in fish tissue are expected to be met by 2055. Milestones will be established and evaluated along the way.

Management activities target primarily DDT. However, PCB actions are being implemented, such as education, PCB transformer recycling, cleanup of old PCB sites, pesticide pickup days, etc. PCBs levels will also be followed.


  • The Lake Chelan Watershed DDT and PCB TMDL Water Quality Improvement Report was approved by EPA on September 11, 2006.
  • The final Implementation Plan was submitted to EPA on August 5, 2008.


  • Lake Chelan Total Maximum Daily Load for Total Phosphorus was approved by EPA January 26, 1993.

Technical information

Unless otherwise specified, the following documents are Ecology publications.



Related information

WA Dept. of Health Lake Chelan Fish Consumption Advisory Fact Sheet #334-082. 2010

Reducing Phosphorus Pollution to Improve Water Quality (Water Quality web site)

WRIA 47: Chelan Watershed Information (Environmental Assessment Program web site)


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Last updated August 2016
  Water resource inventory area (WRIA) 47 map, Washington State.


WRIA(s): #47 (Chelan)
County: Chelan

Water-body Name:
Lake Chelan


# of TMDLs:
Phosphorus - 1

DDT/PCB - Approved by EPA, has implementation plan
Phosphorus - Approved by EPA, has implementation plan

Contact Info:
Lynda Jamison
Phone: 509-575-2434
Email: Lynda.Jamison@ecy.wa.gov

Central Region
Department of Ecology
1250 West Alder Street
Union Gap, WA 98903-0009