The Green River Municipal Watershed

Water for Today, Water for the Future

The Green River Municipal Watershed has been Tacoma Water’s primary water supply since 1913. The watershed is located on the west flank of the Cascade Mountains between Chinook and Snoqualmie Passes and covers about 148,000 acres of forestland. Rain and snow falling on the watershed soaks into the ground and is filtered through natural processes before flowing into small creeks and streams, eventually reaching the Green River.

At the western end of the watershed is the Tacoma Headworks Diversion Dam, located about three miles upstream of Kanaskat-Palmer State Park in King County. This is where we divert some of the water for our use while ensuring there is enough available for fish downstream.

We also operate seven wells within the watershed along the North Fork of the Green River. These wells were formerly used to meet Tacoma’s needs when the water in the river was too cloudy. However, with the construction of the Green River Filtration Facility in 2015, water from the North Fork Wells is now blended with river water to reduce filtration costs.

The Green River Municipal Watershed is also the source of water for a regional partnership formed in 2002 by the City of Kent, the Covington Water District, the Lakehaven Water and Sewer District and Tacoma Water. The Regional Water Supply System supplies up to 65 million gallons per day to Tacoma Water and our project partners.

Watershed Management and Protection

Lands in the municipal watershed are owned by a variety of public and private entities including Tacoma Water, which owns approximately 11% of the lands. Our land is strategically located around the Green River, major tributaries and mountain lakes to protect water quality and preserve fish and wildlife habitat. We have agreements with federal, state, tribal and private landowners and utilities to limit watershed access. This includes carefully controlling activities in the area such as recreation, road maintenance and logging. These partnerships offer significant protection against contamination and helps keeps the supply pure and clean.

Water quality is also protected by the rugged and remote terrain of the watershed, which helps minimize disruption and outside contamination. Gates and guards further limit public and commercial access to the watershed. We evaluate water quality throughout the treatment process, including taking weekly samples from tributary streams that feed the Green River, to help anticipate problems and discover issues before they reach our treatment facilities.

Healthy Forests Provide Clean Water

There is a direct connection between healthy forests and clean water. When rain and snow fall on healthy forests, the water seeps into the soil, goes through a natural filtering process and then slowly releases into stream channels. However, precipitation that falls on bare earth and hardened soils causes immediate runoff and erosion and deposits too much silt and debris into streams, which damages fish habitat. Properly managing our forest lands helps ensure the quality of the water coming out of your faucet and protects sensitive fish and wildlife species and their habitats.

The effects of climate change make forest and watershed management more challenging. To address this, we reduce the number of forest roads, carefully manage and invest in forest health and soil management and look for ways to continually improve our environmental stewardship.

Our primary watershed management strategies are described in the Tacoma Water Habitat Conservation Plan, which was approved by the federal government in 2001. This 50-year plan is a significant step forward for Tacoma Water. It provides clear regulations for us to follow and demonstrates a strong commitment to environmental stewardship. We protect 32 fish and wildlife species by following numerous conservation, monitoring and research measures in water flow management, fish and wildlife habitat enhancement and forest and land management.

Watershed management is also guided by the Green River Watershed Management Plan and Wellhead Protection Program, which help us aggressively protect our community’s water supply.

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