Accumulated state of the Yukon River watershed: Part I critical review of literature

Abstract

A consistent methodology for assessing the accumulating effects of natural and manmade change on riverine systems has not been developed for a whole host of reasons including a lack of data, disagreement over core elements to consider, and complexity. Accumulated state assessments of aquatic systems is an integral component of watershed cumulative effects assessment. The Yukon River is the largest free flowing river in the world and is the fourth largest drainage basin in North America, draining 855,000 km(2) in Canada and the United States. Because of its remote location, it is considered pristine but little is known about its cumulative state. This review identified 7 "hot spot" areas in the Yukon River Basin including Lake Laberge, Yukon River at Dawson City, the Charley and Yukon River confluence, Porcupine and Yukon River confluence, Yukon River at the Dalton Highway Bridge, Tolovana River near Tolovana, and Tanana River at Fairbanks. Climate change, natural stressors, and anthropogenic stresses have resulted in accumulating changes including measurable levels of contaminants in surface waters and fish tissues, fish and human disease, changes in surface hydrology, as well as shifts in biogeochemical loads. This article is the first integrated accumulated state assessment for the Yukon River basin based on a literature review. It is the first part of a 2-part series. The second article (Dubé et al. 2013a, this issue) is a quantitative accumulated state assessment of the Yukon River Basin where hot spots and hot moments are assessed outside of a "normal" range of variability.

Accumulated state assessment of the Yukon River watershed: Part II quantitative effects‐based analysis integrating western science and traditional ecological knowledge

“…Evident in both the reference condition confidence intervals and outliers from upstream to downstream, nitrate loadings are higher at the ECY reach than the WCY reach in the YR. This could be due to the Dawson City hotspot identified in Part 1 of this series (Dubé et al ). Dawson City has historically discharged wastewater effluent of poor quality (R v. C ), which contributes elevated levels of nitrate to the YR that are diluted downstream in the WCY reach.…”

“…Significant LT trends in flow were found in the upper 3 reaches of the YR (YHW, UYR, and ECY) and all were in the positive direction. These increased flows could be evidence of warming temperatures in the Arctic region contributing to greater rates of snow and glacial melt and permafrost thawing (Peterson et al ; Raymond et al ; Dubé et al ).…”

“…For many of the water quality variables, multiple data points were identified as outliers or hot spots and hot moments that fell outside the reference (or benchmark) condition calculated for a particular season. The occurrence of these outliers in time can be put into a spatial context when compared to the major hot spots identified in the YR basin in the literature review in Part 1 of this series (Dubé et al ). In particular, the LYR reach in seasons 2, 3, and 4 (May–September) exhibited the highest frequency as well as magnitude of changes in TOC, TP, and nitrate.…”

“…This is often the required circumstance when previous data from before (or lesser) landscape development are not available for comparison and/or when clear causes of impact cannot be identified for the measured parameter and thus “impacted” data cannot be identified and removed from the reference condition calculation. From Part I of this study (Dubé et al , this issue), hot spots for environmental impacts were identified but clear links to parameters for LT water quality data sets could not be clearly established. Thus we must essentially “accept” the starting point for setting the reference condition based on the data available and adaptively manage that as the point for comparison into the future.…”

“…This is the second article of a 2‐part series. The first article, “Accumulated State of the Yukon River Watershed: Part I Critical Review of Literature” reviewed extensive literature on the YR Basin and identified hotspot areas through time affected by cumulative impacts (Dubé et al ). It also identified limitations of existing data sets for conducting CEA.…”