Discussion

This study aimed to assess the impact of climate change on drought characteristics in the Loire basin by analysing drought duration and deficit under different climate scenarios. In this chapter, these findings are interpreted using the sub-research questions defined in the objective of this research. Additionally, the limitations of the methodology and results are discussed.

The goal of the first research questions was to define the characteristics of droughts in the Loire basin. This was accomplished determining a critical water flow. Since the critical water flow for the chosen station had not yet been defined, it needed to be estimated. This estimation was based on mean monthly data from another station, as daily data was not available. Consequently, this approach may have resulted in a slightly inaccurate critical water flow, since daily fluctuations, which are important for defining a critical flow, were flattened out by relying on monthly averages. Furthermore, droughts were defined based on duration and water shortage. While this definition provided a clear structure for quantifying drought severity, it may have excluded other relevant factors, such as river water temperature and groundwater influences.

The chosen model for this research was the HBV model. As mentioned in the calibration phase of this research, the model seems to have a good understanding of the hydrological system of the basin. For this research the model was sufficient since the model was reliable and easy to implement. More advanced hydrological models were not considered because of the limited research period and access on eWaterCycle. Nevertheless, implementing other models could have provided a useful comparison to assess the reliability of the HBV model.

The second and third sub-research question examined past and future drought occurrences in the Loire basin. Results indicated that historical droughts were less frequent and less severe compared to future projections. This aligns with findings from previous studies (e.g., Dayon et al., 2018 and Debein, et al.,2024) suggesting that climate change is expected to intensify drought conditions in the Loire catchment.

Furthermore, the reliability of the results could be further analysed since a correction factor was required to align the modelled droughts with the return period. A reason for this correction factor can be explained by bias from the CMIP6 forcings, as this model has known issues with simulating rainfall (Chai, et al., 2021). Consequently, this led to slightly different discharge values. Additionally, only one ensemble member was used for the CMIP6 forcings. Exploring multiple ensemble members could provide more insight in the uncertainty of future droughts.