ClimateChange Assessment Guide.pdf - University of Waterloo

Appendix E E-17Subwatershed 19 Case StudyThe groundwater model MODFLOW was used to simulate steady state groundwater conditions for the subwatershed.Based on hydrogeological investigations, groundwater simulations were made and yielded information on the steadystate transfer of groundwater between catchments and across subwatershed boundaries. Based on thesesimulations, it is clear that there is significant movement of water into or out of the subwatershed and across somecatchment boundaries. Subsurface transfers of water across the subwatershed boundaries must be taken intoaccount to establish an accurate subwatershed water balance. Figure 3-2 shows the subwatershed with the majorgroundwater transfers and groundwater pumping sites indicated. In this figure the width of the arrows is looselyproportional to the total transfer rates. These transfers are based upon long-term steady state simulations. Pumpingrates were taken from recent records (AquaResource Inc., 2008).Well 12/ TransmetroEBNFLO EnironmentalFigure 3-2: Transboundary groundwater fluxes included in streamflow model.Overall, there is significant movement of groundwater from the northern catchments of Subwatershed 19 to theNottawasaga Watershed to the north. About 13,000 m 3 /d of groundwater is estimated to discharge to theNottawasaga system. Other major transboundary groundwater flow occurs along the western boundary and is likelydue, in part, to the groundwater table drawdown caused by municipal groundwater pumping wells in the area. In totalabout 9,400 m 3 /d of groundwater is pumped from wells along the western side of the subwatershed.Transboundary losses of groundwater totals about 14,600 m 3 /d, while about 9,400 m 3 /d is pumped from municipalwells. These losses are partially offset with transboundary groundwater inflows of about 12,600 m 3 /d. The WPCPdischarges (12,000 to 13,000 m 3 /d) return all of the pumped groundwater and more to the river.The streamflow model was setup to account for the net effects of transboundary groundwater flow and groundwaterpumping to ensure that the overall water balance is accurate.