Modelling current and future water resources availability of the river Rhine

The Rhine catchment's water resources are likely to continue to experience considerable pressure from growing irrigated land. Concerns regarding the current and future status of water availability to balance conflicting water allocations for maintaining ecosystem services, shipping, and biodiversity are highlighted as freshwater resources become more limited. Contrary to other sectors, agricultural water consumption primarily consists of actual evapotranspiration, resulting in only a small amount of flow returning to receiving water bodies. As a feasible alternative, actual evapotranspiration is therefore increasingly used to quantify agricultural water use.  In hydrological models, agricultural water demand is typically assessed by the volume of water required to fully restore soil moisture to predefined thresholds for sustaining optimal crop growth, under the assumption that there will be enough water available during the growing season to fulfill the demand. However, the assumption of ideal crop growing circumstances (close to potential evapotranspiration) is not necessarily true in dry season, when limited water supply influences irrigation decision-making and will lead to inaccurate estimation of actual water use. This PhD research, as part of the HorizonEurope project Stars4Water, aims to produce historical spatiotemporal estimates of agricultural water use over the Rhine catchment by using satellite observations. To isolate the actual evapotranspiration due from irrigated land, the actual evapotranspiration from the hydrological model wflow_sbm without irrigation scheme will be compared against the actual evapotranspiration derived from satellite retrievals. Land surface temperature observations will be assimilated to constrain the actual evapotranspiration estimates to consider the relationship between the water and energy balance.