Impact of climatic variation on infiltration rate under an arid climate: case of Northern Gafsa Watershed, Tunisia.

The assessment of the impact of climate change on hydrological systems and their water resources, whether at regional or global scale, presents a major challenge in the twenty-first century. Indeed, scientists need to present response elements regarding this climatic variation in order to establish adequate strategies for water resources management. In this context, this study examines the temporal variation of rainfall and its impact on infiltration in the Northern Gafsa Watershed (southwestern Tunisia), characterized by an arid climate. The analysis of the temporal variation of rainfall is based on daily data recorded over the period (1960–2015) at 6 rainfall stations, regularly spread over the study basin. The different components of the hydrological cycle (initial abstraction, infiltration, actual evapotranspiration and runoff) are estimated by WetSpass-M model. The analysis of the daily rainfall data showed that more than half of the daily rainfall contributions are less than 5 mm/day. On the other hand, the results of the WetSpass-M model show that the minimum infiltration rates exceed 40 mm/year, while the maximum actual evapotranspiration does not exceed 108 mm/year despite arid conditions. The maximum runoff and interception rates are 80.1 and 16.9 mm/year successively. Regression models relating monthly infiltration to rainfall and infiltration of previous months were developed. Both calibration and validation phases resulted in reasonably good agreements between infiltration rates estimated by the proposed regression equations and WetSpass-M model. [ABSTRACT FROM AUTHOR]