cQ2 – Climate change impacts on runoff (Q) in Québec

Anticipated natural and anthropogenic changes to the climate of Québec are and will further perturb the hydrological systems of the province. Todays various actors in the water sector will be challenged to redefine their operational management practices by responding to these changes with an elaborate adaptation plan. This project unites these actors – Hydro-Québec, the Québec Water Authority (DEH) adn Rio Tinto Alcan – to streamline their approaches to this challenge in order to establish inter-comparable data and processes for the assessment of climate change impacts on water resources.

This includes the agreement on a common database of observed climate and hydrology, a set of climate projections for the future as well as joint approaches for climate simulation post-processing and analysis of the results. Through the application of hydrological models of different complexity over the same watersheds the questions arising with respect to uncertainties related to these impact models are equally addressed.

Photo : DEH / MDDELCC

• Exploit the latest available climate model simulations data to feed hydrological impact models;

• Harmonize the approach of post-processing of these climate data in order to be able to produce comparable results between each collaborator;

• Establish a common data base for climatological and hydrological observations;

• Advance the knowledge about the possibilities and limits of the assessment of climate change impacts on hydrology;

• Create a state-of-the-art portrait of anticipated hydrological changes for the watersheds of Québec.

• Identification of respective watersheds for each collaborator;

• Generation of bias corrected and downscaled climate projections for each watershed;

• Definition of a common set of indicators for the assessment of hydrological changes;

• Definition and assessment of uncertainty in the modeling chain and communication of this uncertainty;

• Identification of differences of results as a function of post-processing procedure and hydrological models applied;

• Wide communication of the results and public availability of the generated climatological and hydrological data base;

• Update of the common data base as new climate data become available.

The (cQ)2 collaboration has produced a first and second generation of a portrait of the future hydrology of Québec, based on the CMIP3 and CMIP5 climate model ensembles, respectively. The first generation includes the assessment of available Regional Climate Model output from the Ouranos in-house simulations as well as the NARCCAP ensemble.

Results indicate a north-south gradient of changes to future water availability, with an increase in the north and a stagnation or reduction in the south. While the assessment of mean annual water availability, changes in spring flood volume and timing can be well established, larger uncertainty was identified for summer and fall high waters and the duration and severity of drought.

Results from the second phase establishing seasonal median changes in runoff using the CMIP5 ensemble are shown in Figure 1. In this phase of the project the focus lies on improving the information on the latter indicators and the exploitation of the latest Regional Climate Model Ensembles (CORDEX).

Figure 1. Median changes in runoff by season (left column) and the percentage of climate change scenarios indicating an increase in runoff (right column)

Harmonizing the efforts of the various actors in the water sector of Québec creates valuable synergie and streamlining of the knowledge about the impacts of climate change on water resources. It also combines and redistributes the know-how about this complex issue. For the first time comprehensive maps of future water availability and anticipated changes to the hydrological systems of Québec are being made available.