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Hydrological modeling is an effective tool for predicting the hydrological response of watersheds in order to develop appropriate water resource management strategies. Various modeling techniques are available to simulate rainfall-runoff processes in ungauged basins, including regionalization of hydrologic model parameters. Regionalization by spatial proximity (SP) and physical similarity (PS) were chosen for this study to be used with Hydrologic Modeling System (HEC-HMS), which is semi-distributed hydrological model, to evaluate the performance of the model in simulating sub-basin flows as well as the applicability of averaging methods in the case of ungauged sub-basins. Eight sub-basins belonging to the large Cheliff watershed were selected using available data from the period 2007 to 2012. In order to perform a controlled regionalization, one of the eight sub-basins (Wadi Tikzal) was assumed to be ungauged, and five sub-basins were selected to be donors by the (SP) regionalization method and five others by the (PS) regionalization. The results were compared to the original gauged sub-basin series. The performance analysis was carried out through the Nash-Sutclife Efficiency (NSE), the coefficient of determination (R2) and the root mean squared error (RMSE). The results of the simulation are generally satisfactory for wadi Tikzal sub-basin. The model adequately simulated the flows in the other sub-basins, during both calibration and validation phases. The results obtained showed that the regionalization methods used in this study, with the arithmetic mean and the inverse distance weighting (IDW), yielded good results with NSE and R2 values exceeding 0.75 and RMSE values were close to 0.20. The arithmetic mean gave higher results compared to the IDW method, the mean of NSE between the two methods is 0.68 for the arithmetic mean and 0.65 for IDW, and R2 of 0.69 for the arithmetic mean and 0.65 for IDW. The obtained results demonstrate that the regionalization by spatial proximity and physical similarity, using the HEC-HMS hydrological model can be effectively used to predict streamflow in ungauged watersheds, leading to effective water resources management, which enriches the literature regarding the flows regionalization, averaging methods and HEC-HMS performance, in ungauged sub-basins and especially in the northern Algerian region.
Keywords: Arithmetic mean; Cheliff basin; HEC-HMS; Inverse distance weighting; Physical similarity; Regionalization; Spatial proximity.