Climate-analogy mapping as a tool to develop a temporally adaptive hydrological model for the Meuse basin for more reliable predictions under change
by Ellis van Noppen
Climate change leads to changes in temperature and precipitation, resulting in magnitude- and phase-shifts between the annual cycles of precipitation water supply and atmospheric water demand. At the eco-system scale, vegetation actively and continuously adapts to such changing hydro-climatic conditions to ensure sufficient and continuous access to water to survive dry periods. One critical adaptation strategy is the adaptation of root-systems, which determine the root-zone storage capacity, i.e., the soil pore volume that is accessible for plants to extract water for transpiration. This sub-surface property is at the core of any terrestrial hydrological system as it regulates the water storage, release dynamics and in particular the partitioning of water into evaporative fluxes and drainage. As such, the root-zone storage capacity is also a key parameter in hydrological models.
Such hydrological models are also used to quantify the impact of climate change on the hydrological response. In the absence of information on the future properties of the system, this is typically done by calibrating these models to current day conditions and then using the calibrated model together with regional future climate projections to predict the future hydrological response. This procedure implicitly assumes that the properties of the hydrological system do not change over time, which contrasts with vegetation actively adapting its root-system and thus the model parameter describing the root-zone storage capacity to a changing climate. This assumption can introduce potentially considerable uncertainties.
The aim is to decrease these uncertainties by developing the first step towards estimating temporally adaptive, vegetation-related parameters for a process-based hydrological model of the Meuse river basin. The method will be based on recent research in which it was convincingly shown that the catchment-scale root-zone storage capacity can be estimated based on climate characteristics and long-term water balance data. Trading time for space and adopting a climate analogy mapping approach, we will infer vegetation adaptation and the associated changes in root-zone storage capacity for the Meuse basin, from identifying regions in the world where the current day climate resembles the projected future climate in the Meuse basin. Transferring this information back to the Meuse basin will then allow to generate scenarios of root-zone storage capacity adaptation trajectories as a function of time.