A MULTI-YEAR STREAM TEMPERATURE ANALYSIS IN THE WOLF CREEK RESEARCH BASIN, YUKON TERRITORY

Abstract

Water temperature is an important stream characteristic that has a significant impact on the biological and chemical processes within an aquatic ecosystem, and it is sensitive to changes in climate and hydrologic regimes. Stream temperature dynamics are driven by heat exchange processes with the atmosphere and the interaction between surface water and groundwater, and it is uncertain how thermal regimes in northern environments will change under a warming climate. The objective of this thesis is to evaluate summer stream temperature variability in the Wolf Creek Research Basin (WCRB), and investigate relationships between stream temperature and hydrometeorological variables. Long-term stream temperature data for the WCRB in Yukon Territory, Canada was collected from 2002 to 2019 at both the outlet of Wolf Creek (WC), and for one of its high-elevation tributaries, Granger Creek (GC). Linear regression models were developed to explore relationships between stream temperature and various predictor variables at monthly and seasonal scales. The incorporation of an autoregressive term into regression models determined the importance of accounting for the autocorrelation structure of daily measurements, when considering annual regression coefficients. Model selection identified air temperature as the primary predictor variable for daily stream temperature, with streamflow and precipitation having variable inter-annual influences. Monthly stream temperatures at Granger Creek were related to air temperature, date of snow disappearance and antecedent stream temperature, whereas Wolf Creek monthly stream temperatures were most strongly related to antecedent stream temperature. These results suggest that the timing of snowmelt, streamflow, catchment thermal memory (as represented by antecedent stream temperature), and seasonal meteorology interact to influence interannual variability in summer stream temperature at the Wolf Creek Research Basin.