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www.hydrol-earth-syst-sci-discuss.net/5/1863/2008/
doi:10.5194/hessd-5-1863-2008
© Author(s) 2008. This work is distributed
under the Creative Commons Attribution 3.0 License.
Modelling water-harvesting systems in the arid south of Tunisia using SWAT
1Institut des Régions Arides (IRA), Route de Jorf, 4119 Medenine, Tunisia
2International Center for Agricultural Research in the Dry Areas (ICARDA), P.O. Box 5466, Aleppo, Syria
3Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, Indiana 47907, USA
4Department of Soil Care and Soil Management, Faculty of Bio-Engineering, 653 Coupure Links, 9000 Ghent, Belgium
Abstract. In many arid countries, runoff water-harvesting systems support the livelihood of the rural population. Little is known, however, about the effect of these systems on the water balance components of arid watersheds. The objective of this study was to adapt and evaluate the GIS-based watershed model SWAT (Soil Water Assessment Tool) for simulating the main hydrologic processes in arid environments. The model was applied to the 270-km2 watershed of wadi Koutine in southeast Tunisia, which receives about 200 mm annual rain. The main adjustment for adapting the model to this dry Mediterranean environment was the inclusion of water-harvesting techniques and a modification of the crop growth processes. The adjusted version of the model was named SWAT-WH. Model evaluation was performed based on 38 runoff events recorded at the Koutine station between 1973 and 1985. The model predicted that the average annual watershed rainfall of the 12-year evaluation period (209 mm) was split into ET (72%), groundwater recharge (22%) and outflow (6%). The evaluation coefficients for calibration and validation were, respectively, R2 (coefficient of determination) 0.77 and 0.76; E (Nash-Sutcliffe coefficient) 0.73 and 0.43; and MAE (Mean Absolute Error) 2.6 mm and 3.0 mm, indicating that the model could reproduce the observed events reasonably well. Discrepancies remained mainly due to uncertainties in the observed rainfall and runoff data. Recommendations for future research include the installation of additional rainfall and runoff gauges with continuous data logging and the collection of more field data to refine the input parameters (soil and land use). In addition, crop growth and yield monitoring is needed for a proper evaluation of the crop growth submodel, to allow the economic assessment of the different water uses in the watershed.
Discussion Paper (PDF, 940 KB) Interactive Discussion (Closed, 4 Comments) Final Revised Paper (HESS)
Citation: Ouessar, M., Bruggeman, A., Abdelli, F., Mohtar, R. H., Gabriels, D., and Cornelis, W. M.: Modelling water-harvesting systems in the arid south of Tunisia using SWAT, Hydrol. Earth Syst. Sci. Discuss., 5, 1863-1902, doi:10.5194/hessd-5-1863-2008, 2008. Bibtex EndNote Reference Manager XML
