(shortened)
Climate change is a well-established problem that humanity is facing in this century. However, predicting and evaluating projected future changes in climate are subject to a range of uncertainties, this is also true when assessing future hydrological conditions. This Ph.D. study focuses on hydrological impacts and modelling uncertainties of two Danish catchments. This is investigated by calibrating a simple lumped hydrological model under non-stationary historical climate conditions. The model showed deteriorating performance for periods outside the period where the model was calibrated, implying that when doing a future impact study, hydrological predictions could be compromised when using hydrological models calibrated on present time series.
The hydrological response to a future high-end emission scenario was also explored. The hydrological model simulations and drought indices analyses showed longer and dryer periods leading to enhanced root zone dryness, lowered river discharge, and decreasing groundwater head elevation increasing the risk of stream flow drought and crop failure. In contrast, wetter winters will lead to increased flood risks.
Finally, the influence of choosing a specific impact study setup was also investigated by simulating and analysing results from three factors; four climate models in combinations with three hydrological models and four land use scenarios. Results showed that the climate model was the dominant uncertainty factor on stream flow and hydraulic head, but also that the hydrological model structure is an important factor for the impact response and contributes to the uncertainty, especially for extreme values. Land use scenario choice is found to have the smallest influence on hydrology of the three. The study highlights the need to encompass several uncertainty sources when evaluating the hydrological conditions in the future. This is especially true if investigating extremes.