Mean Rainfall Variability Effects on the Hydrological Response of Medjerda High Valley (Tunisia)

The present study is an attempt to evaluate the spatial and temporal rainfall variability of the Medjerda High Valley on the hydrological response of the watershed. Mean time series were collected from 1980/1981 to 2014/2015 for 16 rain gauges covering the studied basin. Missing data were reconstructed using the ponderation method. Subsequently, breaks in each rainfall time series were detected by three tests: Pettitt, SNHT and Buishand’s using Xlstat software. These tests and the calculation of rainfall indices reveal an alternation of wet and dry episodes with very high rainfall excesses. Spatial interpolation of rainfall was conducted on an annual, monthly, and seasonal basis by three methods: Theissen polygon, Spline, and ordinary Kriging. The predicted mean precipitation of the Medjerda High Valley was used for the hydrological study. Thus, the variation of the contributions, their relation with the rainfall and their importance to the basin were studied via the hydrological model GR2m. The flow and, consequently, the water resources constitute the hydrological response of the watershed to the rainfall impulses.