Impacts of climate change on irrigation water requirement of date palms under future salinity trend in coastal aquifer of Tunisian oasis

Abstract

In coastal saline areas, many studies ignore salinity problems when quantifying the impacts of climate change on irrigation water requirement. Based on 11 years (2008–2018) of field investigations in a Tunisian coastal oasis, this study simulated the changes in salinity in a coastal aquifer and quantified changes in net irrigation requirement (NIR) of date palm under climate change, considering required changes in leaching requirement. The future salinity in the aquifer was simulated based on sea level rise and changes in aquifer recharge. The study applied a statistical downscaling model (SDSM) to project future climate variables from 2019 to 2050, the SUTRA model to evaluate the change in aquifer salinity, and applied CROPWAT software to calculate NIR. Three climate change scenarios were considered: RCP8.5 (very high emission scenario), RCP6.0 (medium emission scenario) and RCP4.5 (lowest emission scenario). Several useful finding were revealed in this study. First, these three climate change scenarios showed significant trend of increasing annual maximum and minimum temperatures, relative humidity, wind speed, and solar radiation, and a significant decreasing trend of future rainfall. Second, the average aquifer salinity is expected to increase from an average of 4.2 dS m−1 in 2018 to about 5.3 dS m−1 in 2050. Seawater intrusion was identified as the main cause for this remarkable increase. Finally, NIR is expected to increase from an average value of 1459 mm year−1 during 2008–2018 to 1473–1950 mm year-1 during 2019–2050, depending on climate change scenario applied. Increase in aquifer salinity significantly contributed to this rapid increase of NIR. We believe that our results should be considered in developing adaptation strategies to manage future water resources in coastal areas.