International Research Journal of Public and Environmental Health

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Original Research Article

Influence of spatio-temporal variability of soil surface states on the watershed hydrology behavior: A case study of El Hnach watershed in the semi-arid zone of Tunisia

*1HAJJI Olfa, 1ABIDI Sahar, 2HERMASSI Taoufik, 3MOHAMED Raouf Mahjoub and 1HABAIEB Hamadi

1National Agronomy Institute-Tunis (INAT), Rural Engineering Water and Forest Department, Tunisia.
2National Institute for Research in Rural Engineering, Water and Forest (INRGREF)
3Higher Engineering and Rural Equipment School-Medjez El Bab (ESIER), Hydraulics and Environment, Tunisia.

*Corresponding Author’s Email:
Tel: +21621753512.

Article Number:  |   Pages: 63-69  |   Vol.1(3), April 2014   |   DOI:

 Received:  Accepted:  Published:


The objective of this paper is to analyse and understand the hydrological behavior of El Hnach catchment in Tunisia’s semi-arid zone which constitutes 56% grassland, 40% annual crops and the rest being fallow. The OpenFLUID model which is a physically based hydrological model is used for this study. Six events were used for calibration and validation of the OpenFLUID model. Model performance was assessed using the Nash–Sutcliffe efficiency coefficient. A sensitivity analysis was conducted to systematically modify the input parameters to 10%, 25%, 50%, 100%, 125%, 150% and 200% of its initial value. The analysis showed that the model is particularly sensitive to saturated hydraulic conductivity (Ks); slightly sensitive to effective capillary pressure (Hf) and initial soil moisture content (?i). From the simulations representing different flood scenarios, it could be concluded that OpenFLUID model very well reconstitutes the hydrographic events from the soil parameters chosen primarily with Nash coefficient of up to 75%. This paper shows the performance of the OpenFLUID model and the important role played by soil surface conditions on runoff and infiltration in a semi-arid region. However, it also provides an understanding of the hydro-meteorological data in the studied watershed.

Key words: Hydrological model, parameterization, cultivated watershed, surface soil


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