ClimateChange Assessment Guide.pdf - University of Waterloo

Guide for Assessment of Hydrologic Effects of Climate Change in Ontarioxthe following section, tabulates the major steps involvedin conducting a hydrologic assessment incorporatingclimate change.The climate change impact assessment steps include:1. Definition of Problem. This stage is designed to helpestablish the scope of work and the organization ofinformation. It consists of a statement of goals andobjectives, and identification of primary issues andconcerns in the study area; identification of spatialand temporal factors for the study; and a preliminarylisting of data and information needs and sources.2. Select Hydrologic Modelling Methods. This taskincludes the identification of a general hydrologicmodelling approach and the selection of specificmodelling tools. Alternative approaches include theuse of simple to complex streamflow models, linkedstreamflow and groundwater models and coupledor conjunctive models. Modellers must determinethe most appropriate type of streamflow modeland whether groundwater modelling is warranted.Individual hydrologic process models are discussedwith special emphasis on their relevance to climatechange impact assessments.3. Model Setup and Testing. This stage involves dataacquisition, model setup, calibration and validation,and discussion of errors and confidence.4. Select Climate Scenarios. There are numerousGCMs and GHG emission scenarios to choosefrom when conducting a climate change impactassessment. The challenge is to select a subset ofscenarios that represents the larger group, such thatthe level of effort is minimized without sacrificinginformation. A scenario selection method (termedthe Percentile Method) is proposed that provides arationale for selecting GCM - GHG scenarios that arerepresentative of the full set of scenarios availableto the user. The percentile method selects up to10 scenarios on a statistical basis such that five areselected because they represent the 5th, 25th, 50th,75th and 95th percentiles of annual temperaturechange. A second set of five scenarios are chosenat the same statistical levels based on annualprecipitation change. It is possible that one scenariosatisfies more than one criterion and less than 10scenarios in total are selected. This subset of climatescenarios represents the full range of predicted futureclimates and therefore can be used to investigate thecentral tendency among the group of climates as wellas the effect of the more extreme climates (i.e., 5thand 95th percentiles).5. Develop Future Local Climates. Guidance is providedon data acquisition and manipulation, scenarioselection and processing and methods for comparingclimates. It is recommended that climate changeimpact assessments include the following future localclimate scenarios:• Ten GCM change field climates (PercentileMethod);• At least one statistical regression climate usingSDSM;• At least one weather generator climate usingLARS-WG;• The corresponding GCM change field climatesused to generate the SDSM and LARS-WGclimates; and• At least one RCM-based future climate.6. Assessment of Hydrologic Impacts. A procedureis proposed for reviewing simulation results andcomparing current and future conditions. Thefollowing steps are recommended:• Identify reference regime;• Select metrics and identify standards/targets;• Setup future climate model scenario;• Model climate change impacts by scenario;• Compare changes in climates;• Compare hydrologic changes by scenario; and• Consider uncertainty.This section offers an approach to interpreting resultsfrom the full suite of scenarios and dealing withuncertainty. The range of outcomes and the prevailingtrends provide valuable indications of likely futureconditions and necessary coping ranges.7. Recommendations. Suggestions are provided onthe formulation of recommendations. These includerecommendations to fill data gaps, to conduct futurestudies, and to monitor and identify future adaptationmeasures.