The impact of Climate variability on the flow of wadi Boukiou (Tafna, Algeria)

Abstract

Wadi Boukiou watershed is a sub-basin of the Tafna located in Northwestern Algeria, in a region of high climatic variability where drought has an important effect on the hydrological behavior. The work focuses on the impact of this climatic variability on runoff in the study area to determine which indices will be used to monitor the intensity of the drought? Moreover, to estimate the performance of the semi-distributed model in the Boukiou wadi basin. In addition, this study is based on:  The analysis of the temporal variations of the rainfall and hydrological regime.  The assessment of drought: the methodology is based on the use of climate indices (SPI, DI, PN, RAI, MCZI, CZI, Z-score, EDI) with different time steps (annual, monthly, seasonal, daily),  Assess the impact of climate variability on water resources, basing on the rain-flow modeling of the watershed using the HBV Light model. The analysis of rainfall and hydrological data shows the presence of chronological trends, which generate a decrease in rainfall and runoff between 1974 and 1981. The application of different climate indices using Meteorological Drought Monitoring software "MDM" indicates that our basin has experienced wet periods ranging from 1974/1975-1981/1982 and 2008/2009-2017-2018, while dry periods are spread out between 1981/1982-2008/2009 with a trend to dryness. The use of the semi-distributed conceptual model "HBV Light" gave us satisfactory results during the calibration and validation stages, producing a Nash-Sutcliffe coefficient of 75% - 76% respectively. In addition, the values of the coefficient of determination R2 during the two steps are 0.80 - 0.91 respectively.