Impacts of climate change on hydrology and water quality: Future proofing management strategies in the Lake Simcoe watershed, Canada

The impacts of climate change on hydrology and water quality of the Black River, a tributary of Lake Simcoe, Canada, were assessed for the period 2001-2100, by integrating two models, HBV and INCA-P, and using statistically downscaled data from the Global Circulation Model CGCM3 for two IPCC scenarios (A1b and A2). The effectiveness of catchment management strategies was assessed across the 21st century by simulating controls on sewage treatment works and fertiliser applications, and implementing buffer strips and bank erosion controls. Both IPCC scenarios projected greatest precipitation increases during winter (highest in A2), and greatest rises in temperature during summer (highest in A1b) throughout the 21st century. Under both IPCC scenarios, the greater winter precipitation and warmer temperatures resulted both in higher winter flows and in an earlier spring snowmelt event Under scenario A2, the flow regime ceased to represent a river with a significant snowmelt influence by the 2090s. Increasing summer temperatures reduced summer flows (greater under A1b). Despite variability between IPCC scenarios, both projected increases in annual TP loadings into Lake Simcoe throughout the 21st century (greatest during winter). Management scenarios reduced, but did not fully compensate for, the impact of climate change upon Black River TP loads throughout the 21st century. Winter increases were still observed, due to high rainfall and flow. This climatic impact has significant implications for the current management plans which aim to reduce TP loads to the Lake by 30 tonnes. Mitigation strategies should therefore focus on methods for reducing TP loadings during wetter conditions. (c) 2012 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved.