ClimateChange Assessment Guide.pdf - University of Waterloo

Guide for Assessment of Hydrologic Effects of Climate Change in Ontario2change on water resources in Ontario. This processbuilds upon conventional water resource assessmentsby guiding the user in the selection of future climatescenarios, acquiring relevant information, developingfuture climate time series from this information, andusing these future climates to drive hydrologic models.It is assumed that users of this Guide are familiar withhydrologic modelling procedures and are experiencedwith the use of one or more surface water and/orgroundwater models. In this document, hydrologicmodels refer to surface water and groundwater models.The overall objective is to establish a standardprocedure by which water resource scientists andplanners can generate climates to reflect plausible futureconditions under a changing climate and input theseto hydrologic models for the purpose of simulatingsystem response and behaviour. Ultimately, this typeof information is essential for identifying vulnerabilitiesin the system, identifying options for control andadaptation, educating the public, and developingcomprehensive and integrated adaptive managementprograms in many related disciplines. In addition, acommon approach allows for inter-study comparisons,possible data sharing and added efficiencies.The recommendations provided in this document weretested in a case study as part of this project. The CaseStudy involved a full scale test and demonstration of theproposed methodologies in a study area encompassingSubwatershed 19 in the headwaters of the Credit RiverWatershed. Whenever possible, the case study resultswere used to support the recommendations in thisGuide.1.2 Target Users and ApplicationsThe Guide for Assessment of Hydrologic Effectsof Climate Change in Ontario is meant for use byengineers, scientists and planners involved in themanagement of water resource systems in Ontario; itcomplies with the Clean Water Act and the Canada-Ontario Agreement on the Great Lakes. This Guideprovides the step-by-step procedures to setupand conduct assessments using the best availabletechnology and most recent climate change information.This Guide is targeted towards studies that focus onwater balance and supply issues, rather than peak orextreme flows, including studies addressing:• Drinking Water Source Protection;• Permits To Take Water (PTTW) and other waterallocation studies;• Environmental monitoring programs;• Subwatershed studies;• Stormwater management (SWM) Master Plans; and• Dam and reservoir supply and yield studies.The Guide may also be applied to a variety of otherinvestigations in which hydrology plays a supportingrole, using the same fundamental approach as usedin purely hydrologic assessments. For example, suchstudies could include:• Great Lakes studies (Canada-Ontario Agreement,COA);• Remedial action plans (RAPs);• Wetlands/aquatic wildlife studies;• Lakewide Management Plans (LaMPs);• Forest management studies;• Fisheries studies;• River-effluent assimilative capacity determinations;• Aquatic mixing zone/zone of impact studies;• Control and management of navigable waterways(i.e., Great Lakes connecting channels, Trent-Severnand Rideau waterways); and• Agricultural productivity studies.The Guide does not cover the specific techniquesneeded by proponents to assess the effects ofclimate change on the intensity, duration andfrequency (IDF) of rainfall and precipitation events.Some types of hydrological studies, including thoseassociated with floodplain management or planningand analysis of stormwater infrastructure, requirethe calculation of peak catchment or watershed flowusing event-based or continuous modelling with shorttime steps. The approach described in this Guide forconducting climate change impact assessments on waterresources is not intended for these types of studies. Asdescribed in subsequent sections, while the intensity andfrequency of extreme precipitation events is expectedto increase in the future as a result of climate change,climate researchers are currently unable to reliablyquantify the magnitude, timing or character of theseshifts. As these types of changes to the precipitationregime will have impacts on all aspects of hydrologicresponse, from peak flows to annual water budgets, itwill be important to monitor developments in climate