Shallow groundwater salinization risks under climate change: FEFLOW model application in Cebala Borj-Touil irrigation zone, northern Tunisia

ABSTRACT The Cebala Borj-Touil irrigation perimeter in the low valley of the Medjerda River is marked by a shallow saline groundwater rise. The seasonal water salinity shows a high spatial and temporal variation. This study introduces a novel methodological approach dealing with the data scarcity problem in a complex deltaic area, using only available data and numerical models. The numerical model FEFLOW was used to simulate the shallow groundwater flow and salt transfer. Several simulations were run to explore future trends of groundwater salinity under different climate change (CC) conditions. The results show a significant increase in water salinity under all the climatic scenarios. A 15% decrease in precipitation leads to an average increase in salinity of 10–15 g/l. The significant rise in sea level also affects the salinization process. The intrusion of seawater results in concentrations of salinity between 16 and 20 g/l. In addition, the quality of irrigation water has a marked impact, contributing to a significant increase in salinity, reaching a maximum of 15 g/l. These concerning results are to be expected, as the coastal study area is characterized by a semi-arid climate and is increasingly influenced by anthropogenic factors, including irrigation practices and drainage deficiency.