Monitoring and modelling the hydrological behaviour of a reclaimed wadi basin in Egypt

We analysed the hydrological behaviour of a wadi basin in Egypt, whose channel was modified into levelled terraces for cultivation. A yearly data set was used, consisting of weather data, distributed water content measurements in the terraces of the wadi channel, and run-off discharges at the wadi outlet. A modelling approach combining a run-off model and an agro-hydrological model was tested to simulate, respectively, the water stored in the wadi stream bed after a single rainfall event and the depletion of the stored water by evapotranspiration in the period between two subsequent rainfall events. Calibration and validation of the run-off model were based on both basin outlet run-off and distributed water storage measurements. High Nash–Sutcliffe efficiencies were obtained for both distributed channel water storage and outlet discharges, showing the importance of having available distributed storage measurements, besides basin outlet discharges, to obtain more robust model predictions. The soil–plant–atmosphere model was not calibrated as the parameters for the hydraulic properties, all coming from direct measurements, proved to describe effectively the distributed water storages measured in the terraces during the monitoring campaign. It was observed that the terraces (about 100,000 m 3 ) may store up to 50,000 m 3 of water. By considering that in the soil considered, the water content at the wilting point is about 5% and that in July, the soil profile is still able to retain about 40% of the initial volume, most of the water stored may be used by crops for the whole spring–summer period.