Water Quality

Forest surrounds the blue waters of Mowich Lake.
Mowich Lake, located in the northwest corner of the park, is one of the few subalpine lakes in the park that can be accessed via road.

NPS/Steve Redman Photo

The aquatic resources of Mount Rainier National Park are highly significant resources and include 400 mapped lakes, 470 mapped streams, several unique mineral and thermal springs, and about 3,000 acres of marshland and wetlands. Park waters contain a great diversity of flora and fauna and are critical habitat for several native amphibian and fish species; eight species are listed as endangered, threatened, or species of concern. In addition, other wildlife species are dependent on these aquatic ecosystems as an important source of water.

Park glaciers (25 major glaciers covering 35 square miles) feed the headwaters and provide water supplies and hydroelectric power to downstream communities. The glacial system on Mount Rainier is the largest single-mountain glacial system in the contiguous 48 states.

Aquatic resources in the park also serve as sensitive indicators of environmental change. The topography of the park is rugged and steep, consisting mainly of peaks and valleys. Nine major rivers and their tributaries drain down the flanks of the mountain. They include the Nisqually, Puyallup, Mowich, Carbon, West Fork, Huckleberry, White, Ohanapecosh, and Muddy Fork rivers. The Ohanapecosh and Huckleberry are the only non-glacial rivers. All but two park rivers empty into Puget Sound near Tacoma, Washington. The Muddy Fork and Ohanapecosh Rivers are the exception, flowing into the Cowlitz River outside the park, which drains into the Columbia River and on to the Pacific Ocean.

Each major river occupies a deep canyon whose floor is 1,000 to 3,000 feet below the adjacent divides. Valley floor gradients are steep and increase markedly upstream.

The Geothermal Steam Act Amendments of 1988 identified the park as having significant thermal features. These include the hot springs at Ohanapecosh and on the flanks of the mountain near the Paradise and Winthrop glaciers, mineral springs at Longmire, and a thermal lake inside the firn caves on the summit crater of Mount Rainier. Very little information exists on the chemical, physical, and biological characterization of these unique water resources.

Park staff has been monitoring Mount Rainier’s aquatic ecosystems since 1988. The program is designed to document physical, chemical, and biological conditions, to assess the effects of threats such as atmospheric deposition and nutrient inputs, non-native fish stocking effects on native organisms, recreational impacts, and to track long-term trends.


Water Quality Research


Source: Data Store Collection 9217 (results presented are a subset). To search for additional information, visit the Data Store.


Water Quality Science Briefs

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    Last updated: August 2, 2022

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