Evaluating the Performance of Infiltration Models Under Semi-Arid Conditions: A Case Study from the Oum Zessar Watershed, Tunisia

The infiltration process is an essential element of the hydrological cycle and water management. To provide a consideration for selecting an infiltration model and setting parameter values in the Oum Zessar watershed, the effectiveness of four infiltration models—Horton, Philip, Kostiakov, and Green–Ampt—is systematically evaluated using infiltration rate data measured in several field locations. The constant infiltration rate (CIR) of several locations was assessed using the double-ring infiltrometer technique and juxtaposed with values derived from the models. The parametric equations of each model were calibrated using time-series infiltration data obtained from the experimental observations. Excel functions were used to simplify the intricate mathematical calculations of the parameters. The model’s accuracy was assessed using six statistical metrics: Root Mean Square Error (RMSE), Sum of Squared Errors (SSE), Standard Error (STD ERR), and bias, along with the highest values of Nash–Sutcliffe Efficiency (NSE) and correlation (CORR). The greatest values of NSE and CORR, along with the lowest values of RMSE, SSE, STD ERR, and bias, indicate the optimal model. Moreover, the Model Performance Index (MPI) was implemented to evaluate the effectiveness of the modules by providing a clear scoring system for the models. The obtained results indicated that Kostiakov model displays the optimal fitting values on all indicators and locations, and the Horton model showed the second-best fitting values in most of the indicators.