USGS Transboundary River Monitoring in Southeast Alaska

Science Center Objects

The USGS Alaska Science Center operates super gages on the Alsek, Taku, Stikine, Unuk and Salmon Rivers. Discrete water quality, sediment, and biological sampling are also collected at each gage location. Discrete water quality samples are also collected annually at the Canada-Alaska border crossings of the Taku, Stikine, and Unuk Rivers. Water quality data collection began in 2018 on the Unuk River.

Return to Water

Click on each river’s name to access data and more information about each site.

A geologic study is concurrently being conducted by the USGS Alaska Science Center to improve understanding of mineral and geologic potential of study area watersheds. This information will be used to assess watershed potential to contain precious- and base-metal mineralization that may affect water quality.


The Salmon, Unuk, Stikine, Taku, and Alsek Rivers originate in Canada and flow into Southeast Alaska. All five of these rivers support customary and traditional, recreational, and commercial salmon fisheries. Portions of the Stikine watershed and the entirety of the Unuk and Salmon watersheds are located in what is known at the Golden Triangle as it contains some of the richest gold ore bodies in the world. Salmon fisheries contribute an estimated $1 billion into the regional economy annually. These transboundary watersheds are within the traditional lands of several Alaska Native tribes and First Nations people. Salmon have been integral to the cultures and the livelihoods of communities throughout this region for thousands of years.

The quantity and quality of streamflow in transboundary watersheds of Southeast Alaska are important to local Tribes and other stakeholders. The recently completed Northwest Transmission Line in British Columbia has brought power to the southern transboundary region and accelerated mineral exploration and mine developments, which has further increased local and national interest in current and future conditions in these watersheds. There are also some historic mines that are of concern due to acid mine drainage continuing to seep into local surface and groundwaters.

Congress directed the USGS in 2018 to partner with local Tribes and other Federal agencies as necessary in the area to develop a water quality strategy for transboundary rivers impacted by mining activities. Beginning in 2019, the USGS began a study of baseline water-quality conditions in transboundary rivers across the Pacific Northwest, including ongoing studies being conducted by USGS Science Centers in Alaska, Washington, Idaho, and Montana.

Purpose and Scope

This baseline assessment and continuous monitoring project will collect data to characterize water quality conditions to facilitate future assessments of potential impacts from upstream mining activities. The term “baseline” refers to current conditions of the Salmon, Alsek, Stikine, Taku, and Unuk Rivers in Alaska, which may have already been affected by upstream mining activities that date back to at least the 1860s. Characterization of baseline conditions in transboundary rivers will be accomplished through (1) assessment of the geology and mineralization potential of study area watersheds, (2) retrospective analysis and new data collection to characterize the water, sediment, and biological quality of the Salmon, Alsek, Stikine, Taku, and Unuk Rivers, and (3) the establishment of partnerships with tribes and government agencies to ensure that assessments meet the needs of Tribes and local stakeholders.

Study Area

USGS Alaska Transboundary Rivers DEM

DEM of the five watersheds in the USGS Alaska Transboundary Project. The topography is mountainous, and elevations range from sea level at the river outlets to 13,450 feet in the Alsek watershed. Hydrography reflects the mainstem of each river and major tributaries.(Public domain.)


Other USGS Transboundary Rivers Projects

Pacific Northwest Transboundary Projects
USGS Montana Transboundary Project
USGS Idaho Transboundary Project

Collaborators and other transboundary river investigators

Central Council of the Tlingit and Haida Indian Tribes of Alaska (CCTHITA)
In response to the opening of Red Chris and increased mining pressure in the Stikine, Central Council of Tlingit and Haida (CCTHITA) started a five-year discrete water quality project in November 2015 with monthly sampling in ice-free periods on the Stikine and Taku Rivers. CCTHITA started sampling the Alsek River in June 2018. They sample two sites per river on the Stikine and Taku rivers. Water samples are collected at the surface and at five and ten feet below the surface. Parameters such as water temperature, pH, turbidity, dissolved oxygen, and specific conductance are collected at the time of sampling. Samples are sent for laboratory analyses for a suite of constituents which include dissolved and total metals, nutrients, and organic pollutants. Fine sediments are sampled annually.

Yakutat Tlingit Tribe (YTT) and the Yakutat Forelands Project. Their sampling program is similar to that of CCTHITA for the Alsek. YTT began sampling the Alsek in September 2018.

Ketchikan Indian Community

Wrangell Cooperative Association

Taku River Tlingit First Nation (TRTFN)
TRTFN is planning remediation efforts of mine sites on the Tulsequah River. TRTFN began sampling water, sediment, and fish tissue annually in October 2019. 

Flathead Lake Biological Station at the University of Montana (FLBS)
FLBS scientists actively study the impacts of mining on rivers shared between British Columbia, Alaska, Washington, Idaho, and Montana. Activities include the development of long-term ecological monitoring plans and creating collaborations that increase the capacity for conducting science and applying to environmental decision-making in transboundary watersheds.