Effects of excessive irrigation of date palm on soil salinization, shallow groundwater properties, and water use in a Saharan oasis

In arid oases, soil salinity and a rise in shallow groundwater are serious threats to long-term sustainability of irrigated agriculture. Understanding the impacts of irrigation practices on soil salinity and shallow groundwater dynamics is critical for improving soil conditions and water efficiency. In this study, the impacts of excessive irrigation of date palms with low-quality water on soil salinization and shallow groundwater properties (depth and electrical conductivity) were evaluated for a 10-year period (2005–2015) in a Saharan Tunisian oasis. The study included three phases: (1) assessment of the suitability of groundwater for irrigating date palms; (2) quantification of the long-term water use of date palm plantations; and (3) quantification of dynamic patterns of soil electrical conductivity and shallow saline groundwater in the studied oasis for a 10-year period (2005–2015). Results of this study indicated that under high evapotranspiration conditions, the identified low-quality water resources (leading to high soil salinization risk) coupled with rapidly rising shallow groundwater at critical depths (<1.5 m) (resulting from the high water use) were key factors of the rapid increase in soil salinization within the oasis. The soil electrical conductivity built up to levels that exceeded the salt tolerance of date palms, estimated at 4 dS m⁻¹. Although the excessive use of irrigation water dilutes the groundwater, and its salinity decreases, the risk of increasing soil salinity is greater because of rising water table.