ClimateChange Assessment Guide.pdf - University of Waterloo

Background172.3.6 Dams/ReservoirsClimate change has the potential to alter both thefrequency and magnitude of extreme events, bothof which are critical dam design criteria. Hydrologicimpacts associated with extreme events include changesin the quantity and timing of river flows, increasedreservoir evaporation, decreased snow/ice cover depthand duration, and timing of spring melt. As dams aredesigned to operate over a long period of time andmany were built well before climate change becameapparent, climate change may impact the assumptionsmade with respect to dam design and operatingprocedures. Climate change impacts could affectthe operation, effectiveness and safety of all types ofhydraulic dams.In addition to extreme events, seasonal shifts instreamflow should likely be considered whenestablishing a reservoir’s operational rule curves.Operational rule curves dictate to the reservoir operatorwhat the appropriate water level should be at any givenday throughout a year. In multi-purpose reservoirs,designed to provide both flood protection andhydropower generation/low flow augmentation, the rulecurves are designed to maximize the effectiveness of thestructure for all purposes. For such reservoirs, rule curvestypically specify a low elevation during winter months, toallow flood reduction during the spring freshet period,and a high elevation in late spring, to ensure adequatewater to maintain hydropower generation or low flowaugmentation throughout the summer (Figure 2.5). Sinceclimate change will likely alter the annual pattern ofrunoff, the rule curve will require modification to remaineffective.Figure 2.5 Example reservoir rule curve Grand River Conservation Authority (data source at http://www.grandriver.ca/index/document.cfm?sec=2&sub1=0&sub2=0)