ClimateChange Assessment Guide.pdf - University of Waterloo

E-54Guide for Assessment of Hydrological Effects of Climate Change in OntarioFigure 7-3: Water Quantity Threats Identified in the WHPA Q1 and WHPA Q2. The process of completing a Tier Three Risk Assessment includes a series of water demand and climate scenariosdesigned to assess the capability for municipal wells or intakes to meet their future demands. For groundwatersupplies, a three-dimensional groundwater flow model is simulated in long-term transient mode in order to assess thegroundwater conditions at wells during average, wet, and dry (drought) periods. Groundwater levels are estimated atthe locations of municipal wells to determine if wells will be able to pump their allocated rates during dry, or droughtperiods.While the Tier Three Local Area Risk Assessment for Subwatershed 19 has not been completed at the time of thiscase study, the purpose of this example is to illustrate how climate change scenarios could be considered within aTier Three assessment. This case study considers an example where the groundwater flow model is run for a longperiod of time using groundwater recharge rates estimated for the 12 climate change scenarios. The dailygroundwater recharge rates estimated using the HSP-F streamflow model are aggregated into a time series ofmonthly values and applied to the groundwater flow model over the 1961-1990 time period.Figure 7-4 illustrates the change in the elevation of groundwater at a municipal well over a 30 year period for each ofthe global climate models considered (Table 7-3). The results show that the water levels predicted by each of theclimate scenarios reflect drought conditions during the first five years. There is a wide range of estimated water levelelevations 20 years into the scenarios.