Environmental flow assessment in the context of climate change: a case study in Southern Quebec (Canada)

Abstract

Through a case study in Southern Quebec (Canada), the assessment of environmental flows in light of the effects of climate change is investigated. Currently, the 7Q2 flow metric (7-day average flow with a 2-year return period) is used for water abstraction management. Several flow metrics were calculated using flow time series simulated by a deterministic hydrological model (HYDROTEL) and climate change scenarios as inputs. Results were compared within homogeneous low flow regions defined using ascendant hierarchical clustering, for the 1990, 2020 and 2050 horizons and annual, summer and winter periods. The impact of each flow metric on the potential availability of physical habitat was analyzed using the wetted perimeter as a proxy. Results indicated that: (1) the increasing non-stationarity of simulated flow data sets over time will complicate the use of frequency analysis to calculate the 7Q2 flow metric; (2) summer low flow values are expected to be lower than winter low flows; and (3) flow-duration curve metrics like the LQ50 (median discharge value of the month with the lowest flow) may become relevant environmental flow metrics by 2050. Results question current water abstraction management tools and permit us to anticipate future local and regional issues during low flow periods. HIGHLIGHTS This is an environmental flow (EF) study considering climate change effects in Southern Quebec rivers.; Two flow thresholds and a wetted perimeter threshold were used, both theoretical, to compare the results and their impact on how river ecosystems protection may evolve.; Low flow regions defined using multivariate analyses reveal the evolution of low flows between 1990 and 2050 horizons and identified local issues.; Frequency analysis is not recommended for EF assessment in the future, due to the increasing non-stationarity of flow time series with climate change effects.; Water managers should consider adjusting EF approaches to account for climate change effects on low flows in Southern Quebec rivers.;

Keywords

• climate change
• environmental flows
• hydrotel
• low flow regions
• southern quebec
• wetted perimeter