ClimateChange Assessment Guide.pdf - University of Waterloo

Guide for Assessment of Hydrologic Effects of Climate Change in Ontario48for specific time periods. These issues may be expressedin terms of water balance components, water supplyrates, or streamflow rates. Modellers and resourcemanagers should be specific in identifying these issuesor concerns by specifying the following:• Affected hydrologic processes;• Problematic trends;• Metrics used to measure system behaviour;• Economic sectors at risk;• Activities and communities at risk;• Locations of concern or spatial extent of issue;• Temporal components of concern; and• Other factors relating to the perceived issues.This information is critical in summarizing and analyzingthe results of model runs and providing the basisof comparison used in the climate change impactassessment.6.1.3 Spatial ConsiderationsGuidance:Delineate the physical limits of the study area.The physical limits of the study area must be delineated.Spatial considerations include:• Surface and subsurface domains;• Systems that have influence upon the area of concern;• Aquifers that extend beyond watershed boundaries;and• Others considerations including climate zones,political jurisdictions, urban and rural environmentsand ecological zones.The study area may be larger than the area of concern asthe study area should include all systems that may affectthe problem areas or encompass the necessary regionsto develop the hydrologic model boundary conditions.For hydrologic studies, the whole upstream watershedor subwatershed is generally included, as the full area ofinfluence may extend well beyond the area of concern.For studies dealing with aquifer-based concerns, thestudy area may be larger than the watershed area,as aquifer boundaries do not necessarily coincidewith surface water boundaries. Other factors, such asclimate zones, political jurisdictions, urban and ruralenvironments and ecological zones may influence thestudy area delineation.6.1.4 Temporal ConsiderationsGuidance:Identify the temporal considerations and relevanttime factors.The temporal considerations and the relevanttime factors must be identified. The time relatedconsiderations in hydrologic modelling include thefollowing:• Simulation time step lengths ranging fromminutes (peak flow rate simulation for stormwatermanagement studies) to days (large scale waterbalance studies) are dependent upon the requirementfor event-based detail. Detailed hydrologicalmodelling generally requires an hourly time step,as hourly cycles can play a significant role insnowpack behaviour and hourly rainfall intensitiescan dramatically affect runoff and infiltrationcharacteristics. Data availability at short time stepscan be limited; meteorological data are rarelyavailable more frequently than at an hourly time stepand many climate downscaling methods only providedata at daily frequencies.• Dates and length of simulation periods for modelcalibration and verification and for model scenarioruns must be stated. These dates and period lengthsshould be optimized based on the availability ofobservational data; in many cases a preliminarysurvey of data availability is required. Calibration andvalidation period lengths of 10 years or greater arerecommended in surface water hydrologic studies.Groundwater system simulations, however, can lastfor several decades. The extension of simulationperiod lengths should be weighed against the degreeof land use change or other demographic changeexperienced in the study area over the time period.Selected simulation periods also relate to the studyobjectives; for example, water balance studies focusupon long-term average conditions (i.e., decades).