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Hydrological modeling of floods in the Wadi Bechar watershed and evaluation of the climate impact in arid zones (southwest of Algeria)

Bekhira, Abdelghani, Habi, Mohammed, Morsli, Boutkhil
Applied water science 2018 v.8 no.6 pp. 185
arid zones, computers, engineering, evapotranspiration, floods, hydrologic models, meteorological data, overland flow, production functions, rain, runoff, watersheds, Algeria
Precise knowledge regarding the quantities of water available in the Wadi Bechar watershed and better management of this resource is necessary to initiate the transformation of rainfall data into hydrometric data (simulated flow); this is the main objective of the hydrological rainfall–runoff modeling. The primary focus of this paper is the rainfall–runoff modeling on an annual and monthly scale in the Wadi Bechar watershed which covers an area of 6858 km². We employ the rural engineering model (GR) for annual timestep GR1A and for the monthly timestep GR2M. The input parameters are precipitation (P) and evapotranspiration (ETP) calculated by the Turc method; the output parameter is elapsed water slide (Q). The results obtained indicate that the model takes into account the different atmospheric and underground exchanges, as well as the capacities of the production tank and routing tank. With this work, the contribution of precipitation to flows downstream of the watershed can be evaluated and quantified. On an annual scale, the potential evapotranspiration modulator coefficient X is equal to 2.20 > 1. This indicates that the water from the Wadi Bechar watershed seeps into the ground or into the adjacent watersheds of Wadi Zousfana and Wadi Guir. On a monthly scale, we calibrate and cross-validate the model with the selected input data, determining the model parameter sets that best reflect the transformation of rainfall into flow. The calibration was done with several passages in computer. The value of the capacity of the estimated production tank X1 is equal to 4.74 mm, which reflects the production function, and subsequently indicates the rainfall capacity transformed into a water flow available for runoff at the Wadi Bechar watershed scale. The value of the estimated underground exchange coefficient parameter X2 is equal to 0.02; it reflects the transfer function, which indicates the movement of this surface flow toward the watershed outlet.