ClimateChange Assessment Guide.pdf - University of Waterloo

Climate Change Assessment776.4.4 Determine Independent Factors for FutureScenariosIn many watersheds, urban areas will continue toexpand and intensify, land uses will change in urbanand rural areas, watershed management practices willbe modified, and ecosystems will adapt to the evolvingenvironment. Thus, the physical nature of many areaswill evolve and should be considered non-steady overthe time scales addressed with climate change impactassessments. When preparing to setup future conditionsmodels, it is necessary to consider and account forseveral aspects of the watershed beyond future climatealone. Future watershed characteristics that should beconsidered may include:• Land use;• Population;• Water supply sources;• Wastewater discharge volume and locations;• Vegetation;• Agricultural practise (i.e., irrigation, crops);• Technological innovation and adoption (i.e., LIDs,SWM, best management practices, etc.); and• Policy.Hydrologic impact assessment studies would benefitfrom identifying the impacts of climate change onfuture water balance fluxes apart from any influencesof other changing conditions. In such studies, land use,population and other subwatershed characteristicsshould be held at current levels to isolate the impacts ofchanging climates.Guidance:It is recommended that impact assessmentstudies include a climate change impactassessment of the water balance within the studyarea using existing land use, population andstudy area management practices.It is also informative to examine the effects of climatechange on the study area hydrology and water balanceunder future conditions of land use, population andmanagement practices. The combined influences andstresses of future conditions on water supply can beestimated within the uncertainties of predicting trendsin study area development. In fact, if resources allow,additional future development and managementscenarios can be studied to determine the best courseof future development and adaptation.Guidance:All hydrologic investigations should also considerclimate change impact assessments underfuture land use, population and managementconditions to estimate the added stressassociated with these developments andpractices. Future conditions should be realisticfor the climate time horizons.6.4.5 SummaryAfter completing the tasks in this section the modellershould have:• Established a baseline climate;• Selected a suite of GCM-emission scenarios forapplication; and• Considered and developed future conditions, asidefrom climatic conditions, for the future conditionsmodel.6.5 Develop Future Local Climates6.5.1 OverviewIn all comprehensive climate change impact assessmentsof water resource systems, a combination or suite offuture climates must be developed for the study area(see Section 6.4.3.4). For all assessments the IPCCrecommends using multiple climate scenarios derivedusing different methods (i.e., change fields with multipleGCMs and GHG emissions, and downscaling) tocapture the uncertainty associated with various emissionscenarios and various climate estimation techniques.This approach is adopted in this Guide.The approach described herein explores four futureclimate generation methods including: