Annual Precipitation Variability in Semi-Arid Area: The Wadi Cheliff Case Study, Algeria

The spatio-temporal variability of precipitation in the Wadi Cheliff Basin (Algeria) has been evaluated by means of annual time series of precipitation observed on 150 rain gauges in the period 1970–2018. First, in order to identify the natural year-to-year variability of precipitation, for each series, the Coefficient of Variation (CV) has been evaluated and spatially distributed. Then, the precipitation trends at an annual scale have been analyzed using two nonparametric tests. Finally, the presence of possible change points in the data has been investigated. Results showed a similar spatial pattern between CV and the annual rainfall, with a spatial gradient between the southern and the northern sides of the basin. Results of the trend analysis evidenced a marked negative trend of the annual rainfall (22% of the rain gauges for a significant level equal to 95%), involving mainly the northern and the western-central area of the basin. Finally, possible year changes have been identified between 1980 and 1985.