Author(s): Fairouz Slama; Hammouda Dakhlaoui; Emna Gargouri-Ellouze; Ons Sidhom; Nessrine Zemni; Fethi Bouksila; Imen Hassen; Rachida Bouhlila

Linked Author(s): Fairouz Slama, Emna Gargouri-Ellouze, Imen HASSEN

Keywords: Groundwater; Arid regions; Climate model; Recharge; Hydrus1d

Abstract: In arid and semiarid regions groundwater often represents the major water resource. In these regions, the demand for water is constantly increasing. Recharge is an important term in the groundwater balance. But climate change is expected to slow the level of recharge by 10% to 30% by 2070. The present paper aims to study the impact of climate change on groundwater recharge rates using climate and numerical modelling. For this purpose, we chose three groundwater systems located in Northeast and central Tunisia: , Nabeul and Kasserine aquifer system (KAS). Korba and Nabeul coastal aquifers are located in the Cap Bon Peninsula (mean precipitation is 450 mm and mean annual evapotranspiration is 1100 mm), and are overexploited for agricultural purposes. The KAS, located in an arid region in Central Tunisia (mean precipitation is 300 mm and mean annual evapotranspiration is 1233 mm), is a transboundary aquifer extending into the northeast of Algeria. The main regional reservoir of the KAS is the deep Miocene sandstone representing the most available source of water supply in the area. In both study sites, a numerical modelling method (HYDRUS-1D) was applied to estimate the present diffuse recharge rates using climatic and soil field investigation campaigns dataset. One, three and four soil profiles, representing different recharge zones, were selected for Nabeul, Korba and the KAS groundwater systems respectively. Daily mean temperature and precipitation were extracted from 9 regional climate models forced by general circulation model (GCM-RCMs) issued from EURO-CORDEX project. EURO-CORDEX provides the most recent high resolution climate projections for the European domain with a 0.11° resolution (horizontal grid spacing of ~12 km). The period 1970‒2000 corresponds to the historical model simulation. Climate projections were performed over the future periods 2040‒2070 and 2070‒2100, with two radiative concentration pathway RCP 8.5 and RCP 4.5. Quantile Mapping was adopted as the Bias Correction approach for the projected raw daily GCM output. For Korba aquifer, the calculated yearly aerial recharge rate, using HYDRUS-1D, ranged from 0.7 to 6.2 %. For the KAS, model calculations showed that recent recharge rates were between 0.2% and 6.7%. Projected groundwater recharge for Kelibia showed an increase reaching 34 % from 2040 to 2070. From 2070 to 2100, groundwater recharge will decrease of 72.01%. For Nabeul, groundwater recharge will increase by 10.83 % for the period of 2040-2070 and will decrease by 62% for the long-term projected period. Groundwater recharge for the period of 2040-2070 in Kasserine will decrease by 13.58% and 19.57% of the total rainfall for sites P1 and P4 respectively. However, recharge for site P3 will remain null. The recharge will decrease by 22.37%, 57.26% and 22.10% for sites P1, P3 and P4 respectively for the long-term period 2070-2100.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221540

Year: 2022