From the USGS website "
The USGS, National Research Program (NRP) and the USGS Alaska Science Center (ASC) and the Yukon River Inter-Tribal Watershed Council (YRITWC) have been cooperating to collect baseline and process-based water quality data in the Yukon River Basin (YRB) since 2001. During the first 5 years of these efforts the study was supported by the USGS NASQAN Program to establish a water quality baseline for the YRB study to understand the Basin's response to climate change. Climatic warming of the YRB is resulting in lengthening of the growing season, increases in fire frequency and intensity, thawing of permafrost, and deepening of the soil active layer. These and related processes are anticipated to result in changes in water and sediment chemistry and discharge in upcoming decades. A better understanding of baseline trends and processes controlling the water quality of the Yukon River and its tributaries will facilitate the proper management of resources as conditions change in response to environmental change. In a continuing effort to understand these changes, the USGS and the YRITWC continue to monitor water discharge and make water and sediment chemistry measurements on the Yukon River and all of its major tributaries.
From October 2000 to September 2005, the NASQAN Yukon River study collected water samples and measured continuous discharge at five
fixed monitoring stations (three on the mainstem Yukon River and two major tributaries). Each year following, each Fixed Station was sampled seven times (once under ice and six open water) to build a multi-year water quality baseline dataset. During the years 2002-2005, process-based studies (synoptics) were conducted, sampling the entire 2100 mile reach of the Yukon River from headwaters in the Yukon Territory, Canada, to Pilot Station, Alaska, near the outlet to the Bering Sea. Eight additional
mainstem sites and 47
major tributaries were also sampled. Each sampling consisted of a complete suite of water quality samples measuring over 90
constituents. NASQAN, through the ASC, continues to support the Fixed Station at Pilot Station."
