Monitoring Soil Moisture Content of Jessour in the Watershed of Wadi Jir (Matmata, Southeast Tunisia)

Abstract

Soil moisture is an important indicator to determine the potential production of a crop, especially in recurrent drought threatened countries as Tunisia. It is also important in hydrologic modeling of watersheds. In the context of enhancing the value of jessour (plural of jesr), and providing scientific knowledge of the evolution of soil water content in this water harvesting technique, TDR measurements were carried out for four consecutive years at three sites in the watershed of wadi Jir (Matmata, southeast Tunisia). The obtained results show that The jesr ensures water storage in soil, which varies on average between 100 m and 200 mm. However, in wet periods, this storage jesr can exceed 300 mm but can drop as low as 50 mm in dry periods (as recorded in the jesr of Techine). Only one effective rainfall annually can ensure adequate water supply for the rest of the hydrological year. During wet periods, olive trees extract water from upper soil horizons whereas they exploit the deeper horizons during summer and drought periods. The use of the theoretical potential at permanent wilting point of pF = 4.2 seems to be inadequately adapted to olive extraction capabilities and tends to underestimate the amount of water that the adult olive trees can extract. Thus, jessour can adequately ensure water supply of olive trees while ensuring effective erosion control in the mountains of Matmata and landscape ecology enhancement.