Study of Rainfall Variations in Tessa Subwatershed of Medjerda River in Tunisia

The spatial and temporal study of rainfall variation is very important for efficient management of water resource. This subject is discussed in Tessa watershed, a subcatchement of Medjerda the only perennial River in Tunisia. 13 pluviometric gauge stations have been chosen to collect data from 1984 to 2014. Three scales were considered; monthly, seasonal and annual. Gap in data were reconstructed by the mean ponderation method. We tested the homogeneity of the series by the Pettitt, Buiscand and SNHT test via XlStat software. The ruptures are detected in the months of June, July, August and October, in the season of autumn and spring of the years 1994–1995 and 2000–2001. In order to create a spatial distribution of rainfall patterns, two interpolations methods were used; isohyet and Thiessen polygons via the software ArcGIS. In fact, the analysis results illustrate an alternation of wet and dry episodes with very marked excess rainfall, a gradual increase in rainfall. These rainfall fluctuations have contributed to weakening the natural environment. The results show the rainfall pattern of the watershed is a temperate continental regime.