The effect of climate change on the Loire River - Ischa Hollemans

Contents

The effect of climate change on the Loire River - Ischa Hollemans#

Abstract#

This study investigates the impact of climate change on drought characteristics in the Loire River basin. Climate change is expected to intensify drought conditions globally, with significant implications for water resources.

This research aims to assess how future droughts in the Loire basin will evolve under different climate scenarios, focusing on changes in drought duration and severity. To achieve this, the hydrological system of the Loire was analysed to identify drought causes and define drought conditions using a critical water flow threshold. For this research, the station Blois-sur-Loire was selected, with a critical water flow set at 66.5 m³/s. This threshold was applied to detect historical droughts.

An algorithm was developed to calculate both the maximum water shortage and the drought duration, the time required for water flow to return to normal after a drought. This algorithm was used to calibrate the HBV hydrological model on historical data to project future discharge conditions accurately. The model was calibrated based on the distribution of drought duration and deficit. The calibrated model was applied to three future climate scenarios to assess the impact of climate change under different climatic conditions:

  • SSP126: a more optimistic climate future with significant mitigation measures,

  • SSP245: a scenario reflecting limited climate action, and

  • SSP585: a high-emission, fossil-fuelled driven scenario.

The discharges for these scenarios are generated using CMIP6 MPI-ESM1-2-HR dataset in combination with the calibrated HBV model.

The results, analysed using return periods, reveal a clear trend toward more frequent and severe droughts across all climate scenarios, even under the most optimistic scenario (SSP126). However, the results for SSP126 indicate that climate change measures can mitigate drought impacts compared to the less favourable scenarios (SSP245 and SSP585). The difference in drought duration between SSP245 and SSP585 is minimal, likely due to faster replenishment during winter months. However, drought deficits are projected to become significantly more extreme under higher return periods in SSP585.

Uncertainties remain due to the use of only one CMIP6 ensemble member, which may influence the reliability of future drought projections. Future research is recommended to explore multiple ensemble members and assess the implications for water management strategies in the region.

Contents