The GRaCCE project aims to develop a process-based integrated method for determining groundwater recharge and predicting droughts in order to support water management in semi-arid regions in the Middle East. The study area comprises the territories of Israel, Jordan and the Palestinian territories of the West Bank.
The entire region is exposed to enormous water stress and political tensions, as its extremely scarce water resources are partly managed jointly by Israel, Palestine and Jordan, whose management strategies also require cooperation and joint approaches to solutions.
The target region is also characterised by high hydrological variability and evaporation losses, i.e. highly fluctuating availability of surface and spring water and consequently overexploitation of groundwater resources, inadequate wastewater treatment and thus water contamination, as well as constant growth of industry and population, partly due to immigration from war zones.
Porous fractured bedrock aquifers in the study area contain important groundwater resources and require special assessment and modelling methods to capture the highly dynamic and often difficult-to-predict infiltration rates, due to their heterogeneous structure. Previous studies show that the thick vadose zones (several hundred metres) prevalent in the region can be relevant in terms of water management as long-term reservoirs and, if properly considered as a dynamic water resource, which can contribute to mitigating supply shortages during long-term droughts. Due to the dual permeability characteristics of the vadose zone in fracture and karst aquifer systems, i.e. fast and slow pathways and their interaction, quantification of water fluxes through the unsaturated zone is difficult. To characterise infiltration and groundwater recharge, different hydrogeological, geophysical and hydrogeochemical methods as well as modern numerical modelling approaches are combined to determine the available water resources in a management period of about 1 month.
Information from day-based climate modelling, which reproduces the general development of precipitation and evapotranspiration characteristics is taken into account in the forecast modelling for the period 2020 – 2070. The results of these investigations serve as a quantitative basis for the prediction of water deficits in a control volume of the aquifer based on drought indicators and using data assimilation techniques. Integration into a web-based toolbox that includes a drought early warning system and adapted pumping and storage strategies will allow water users and local authorities to improve regional resilience to extreme climate events and minimise water stress.