John Wiley & Sons, Ltd.

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

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This paper is the second in a two‐part series assessing the accumulated state of the transboundary Yukon River basin in northern Canada and the USA. The determination of accumulated state based on available long term discharge and water quality data is the first step in watershed CEA in the absence of sufficient biological monitoring data. Long term trends in water quantity and quality were determined and a benchmark against which to measure change was defined for five major reaches along the Yukon River for nitrate, total and dissolved organic carbon, total phosphorus, orthophosphate, pH and specific conductivity. Deviations from the reference condition were identified as “hot moments” in time, nested within a reach. Significant increasing long term trends in discharge were found on the Canadian portion of the Yukon River. There were significant long term decreases in nitrate, TOC and TP at the Headwater reach, and significant increases in nitrate and specific conductivity at the Lower reach. Deviations from reference condition were found in all water quality variables, but most notably during the ice‐free period of the Yukon River (May‐Sept) and in the Lower reach. The greatest magnitudes of outliers were found during the spring freshet. This study also incorporated traditional ecological knowledge (TEK) into its assessment of accumulated state. In the summer of 2007 the Yukon River Inter Tribal Watershed Council organized a team of people to paddle down the length of the Yukon River as part of a “Healing Journey”, where both Western Science and TEK paradigms were employed. Water quality data were continuously collected and stories were shared between the team and communities along the Yukon River. Healing Journey data were compared to the long term reference conditions and showed the summer of 2007 was abnormal compared to the long term water quality. This study showed the importance of establishing a reference condition by reach and season for key indicators of water health to measure change and the importance of placing synoptic surveys into context of long terms accumulated state assessments. Integr Environ Assess Manag © 2012 SETAC

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