Streamflow regime sensitivity to climate change impacts within Lake Champlain Basin

Lake Champlain Basin serves as a major source of ecosystem services and economic inputs to the northeastern United States. Research on northeastern United States climate indicates that historical trends of warmer air temperatures, increased precipitation amounts and changes in the timing and intensity of precipitation are expected to continue in the 21th century. Lake Champlain Basin might then be affected with seasonal weather shifts caused by significant climatic changes driven primarily by human generated greenhouse gases. This expected 21th century climatic changes might then impact flow regime in the Lake Champlain Basin and hence raise concerns about hydrological, ecological as well as political basin conditions. In this work, we examine alternative possibilities that might emerge in the Lake Champlain Basin streamflow regime given the imminent changes anticipated in climate forcing variables. Three streamflow regime classifications that include high flow disturbance, low flow disturbance and flow variability and predictability (Colwell index) will be analyzed in this work to better understand climate change impacts on streamflow regime within the Lake Champlain Basin. The Mad River near Moretown watershed located at Vermont, United States of America and upstream of United States Geological Survey gauge # 04288000 has been selected to be the study watershed for this work (drainage area about 360 km2). The Regional Hydro-Ecological Simulation System (RHESSys) model will be used to assess how climate changes might impact streamflow regime. The RHESSys model driven by historic precipitation, minimum and maximum air temperature data was first calibrated to daily streamflows at the watershed outlet. Streamflow realizations were then obtained by driving the calibrated RHESSys model with daily scenarios of different climate data to examine streamflow regime changes sensitivity. Our preliminary streamflow realization results at the study watershed outlet suggest that an increase in flood duration periods as well as an increase in base flow index values are likely to occur. Also our results suggest that a decrease in overall flow variability without considering the temporal sequence of flow variation is expected. Streamflow predictability results at the study watershed outlet suggest that a continuation of being due to high constancy (constancy is a measure of temporal invariance) of streamflow which varies little among months and years. In other words, the streamflow discharge at this study gauge is perfectly predictable with all the predictability driven from the constancy component of Colwell index. This work represents a contribution to the conservation community of the Lake Champlain Basin as they begin to plan and respond to the current and future impacts of climate changes on Lake Champlain.