EGU25-10381, updated on 15 Mar 2025
https://doi.org/10.5194/egusphere-egu25-10381
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
How important is diffuse recharge in the Chalk aquitard under desert conditions?
Hala Jmili, Noam Weisbrod, and Tuvia Turkeltaub
Hala Jmili et al.
  • Ben-Gurion University of the Negev, The Jacob Blaustein Institutes for Desert Research, The Zuckerberg Institute for Water Research, midreshet ben gurion, Israel (jmilih@post.bgu.ac.il)

As aridity increases, the importance of focused groundwater recharge becomes more significant. It is well-recognized that groundwater recharge in arid areas primarily occurs during flash floods in ephemeral streams. However, previous studies suggest that diffuse recharge—spatially distributed groundwater replenishment from precipitation or irrigation—may also play a substantial role in aquifers recharge. This study aims to quantify the contribution of diffuse groundwater recharge through unsaturated fractured Chalk under the arid conditions of the Negev Desert.

Three models were evaluated to quantify and understand the processes of diffuse groundwater recharge: the Richards equation, the dual porosity model, and the dual permeability model. The models were calibrated against three unsaturated zone tritium profiles.  Climate data and tritium concentrations in the rain of 1960 to 2023 were prescribed as the atmospheric boundary conditions. The model calibration involved running multiple simulations, incorporating 800 combinations of hydraulic parameters generated by the Latin hypercube sampling method. Model selection and performance were evaluated using statistical metrics, including reduced root mean square error (RRMSE) and the Akaike information criteria. The simulation results indicated that the dual porosity model outperformed the dual permeability and Richards’ equations. This suggests that water flow and solute transport occur within the loess layers and chalk fractures through preferential pathways while highlighting the exchange of water and solutes between the flowing system and the immobile matrix. The calibrated dual porosity models allowed for studying the relationship between diffusive recharge and precipitation. Two cross-correlation analyses (CCA) were conducted: one between yearly rainfall and yearly potential recharge at a depth of 5 meters, and another between all precipitation events above the 95th quantile and the yearly potential recharge at 5 meters depth. Both rain statistical characteristics exhibited similar CCA trends, while the quantile-95 values demonstrated stronger correlation coefficients. This illustrates that heavy rainfall drives deep water infiltration, ultimately replenishing the aquifer.

How to cite: Jmili, H., Weisbrod, N., and Turkeltaub, T.: How important is diffuse recharge in the Chalk aquitard under desert conditions?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10381, https://doi.org/10.5194/egusphere-egu25-10381, 2025.