Applicazione e confronto di due strumenti di analisi per il supporto alla decisione per la valutazione della degradazione del territorio in un bacino idrografico in Tunisia

摘要

The objective of this study was to adapt and evaluate the applicability of a physically-basedspatially distributed hydrological model SWAT (Soil Water Assessment Tool) and IWRMintegrated water resources management lumped model WEAP (Water Evaluation AndPlanning) for simulating the main hydrologic processes in arid environments. The modelswere applied to the 1200-km2 watershed of wadi Merguellil in central Tunisia to investigatethe hydrological response of the basin. The sensitivity analysis of hydrology, soil andvegetation parameters of SWAT and WEAP helped to identify influential parameters and thiscould serve as a guide in calibrating the models. The main adjustment for adapting WEAPand SWAT model to this dry Mediterranean watershed was the inclusion of water soilconservation works WSCWs, which capture and use surface runoff for crop production andaquifers recharge in upstream basins. The models were run and the simulated runoff valueswere compared with the measured stream-flow values. In the calibration period the Nashefficiency coefficient for the SWAT and WEAP models were respectively 0,64 and 0,41 forthe runoff. The value of Nash coefficient indicates that the result of SWAT model isacceptable contrasting the WEAP model. SWAT simulation was better than WEAP in mostcase and could be used with reasonable confidence for runoff quantification in the Merguellilwatershed. For the SWAT model, The results of the water balance simulation at monthly andannual time scales was generally good and the observed stream-flow in Zebess, Skhira,Haffouz and El Houareb flow-gages could be reproduced satisfactorily. An estimation of thesuspended sediments and nutrients loads in the watershed was performed without calibrationbecause of missing data. Several hypothetical scenarios of land use and climate change weregenerated by the SWAT and WEAP models in order to determine the impact of the variationof land management and climate change on water demand and supply on downstream waterusers.