Direct measurements of floodwater infiltration into shallow alluvial aquifers

The relationship between floodwater infiltration and groundwater recharge of a shallow alluvial aquifer in a hyper-arid desert was studied in the Arava valley, Israel. The study implemented an experimental system that simultaneously monitors all three hydrological domains controlling the recharge process: (1) floodwater stages on land surface, (2) water-content variations in the deep vadose zone, and (3) groundwater response to the infiltration. This experimental system makes use of a new technique for installing flexible time-domain reflectometry probes for continuous monitoring of the vadose zone moisture profiles. Water infiltration was monitored in controlled infiltration experiments and during a natural flood. The monitoring setup allowed real-time tracking of the wetting-front propagation velocities and assessment of water fluxes through the vadose zone. The results revealed a complex infiltration process that includes matrix and preferential flow together with lateral flow.