Hadded et al. (2025) Enhancing groundwater resources through managed aquifer recharge: A SWAT application in arid southeastern Tunisia

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2025
• Date: 2025-12-12
• Authors: Rym Hadded, Mongi Ben Zaied, Giulio Castelli, Fethi Abdelli, Bouajila Essifi, Elena Bresci, Mohamed Ouessar
• DOI: 10.1016/j.ejrh.2025.103027

Research Groups

• Laboratoire d’Er´emologie et de LCD (LR16IRA01), Institut des R´egions Arides (IRA), Universit´e de Gab`es, M´edenine, Tunisia
• Dipartimento di Scienze e Tecnologie Agrarie, Alimentari, Ambientali e Forestali (DAGRI), Universit`a degli Studi di Firenze (UNIFI), Firenze, Italy

Short Summary

This study applied the Soil and Water Assessment Tool (SWAT) to simulate hydrological processes and quantify the impact of Managed Aquifer Recharge (MAR) structures, including traditional Water Harvesting Techniques (WHTs), on groundwater recharge in arid southeastern Tunisia, demonstrating that MAR significantly enhances aquifer recharge.

Objective

• To simulate main hydrological processes and quantify water balance components in the Koutine, Gattar, and M´edenine watersheds, with a specific focus on groundwater recharge.
• To assess recharge dynamics and water balance components under pre- and post-Tunisian Strategy for Water and Soil Conservation (SWSC) conditions.
• To determine the relative contribution of each MAR intervention (traditional WHTs, gabions, recharge wells) to total groundwater recharge, providing quantitative insights for sustainable water management in arid Tunisia.

Study Configuration

• Spatial Scale: Koutine, Gattar, and M´edenine watersheds (total area 1281 km²) in the Jeffara plain, southeastern Tunisia, contributing to the Triassic aquifer of Sahel el Ababsa (650 km²).
• Temporal Scale: Two simulation periods: pre-SWSC (1971–1990) for calibration and post-SWSC (1991–2020) for validation and impact assessment.

Methodology and Data

• Models used: Soil and Water Assessment Tool (SWAT) for hydrological simulation; SWAT-CUP with SUFI-2 algorithm for calibration, validation, sensitivity, and uncertainty analysis; SCS Curve Number (CN) procedure for runoff estimation; WXGEN weather generator for filling missing climate data.
• Data sources:
  • Climate: Daily precipitation from 9 rain gauge stations, daily maximum/minimum air temperature, wind speed, and relative humidity from 3 weather stations (M´edenine, Beni Khedache, El Fje). Solar radiation from ERA5-Land database. Daily potential evapotranspiration (PET) from M´edenine weather station.
  • Land Use: Landsat TM imagery (30 m resolution) for 1984 and 2010, processed using supervised classification (CART algorithm in Google Earth Engine).
  • Soil: Soil map of the Jeffara region (Taamallah, 2003), modified by Ouessar (2007) and Ouessar et al. (2009) using Spot XS image (1991) and field investigations.
  • Digital Elevation Model (DEM): SRTM (Shuttle Radar Topography Mission) with 30 m resolution (USGS / NASA, 2000), processed using TauDEM tool.
  • Observed Discharge: Daily streamflow data from Koutine Cassis GP1 gauging station (1973–1996), used for calibration (1973–1990) and validation (1992, 1995).
  • MAR structures: Gabion locations digitized from Google Earth Pro (2012) satellite images. Recharge wells (13 total) represented as reservoirs with parameters tuned to match estimated recharge rates.

Main Results

• Model Performance (Koutine watershed):
  • Discharge calibration: Coefficient of determination (R²) = 0.72, Nash–Sutcliffe efficiency (NSE) = 0.63.
  • Discharge validation: R² = 0.69, NSE = 0.62.
  • PET calibration (pre-SWSC): R² = 0.79, NSE = 0.72.
  • PET validation (post-SWSC): R² = 0.82, NSE = 0.75.
• Land Use Changes (1984–2010): Olive orchards on plains (OLVP) increased by approximately 40%, cereal cultivation (CULT) expanded by 13%, while plain rangelands (STPP) decreased by 39%.
• Water Balance (entire study area):
  • Pre-SWSC (1971–1990): Average annual precipitation 194.5 mm/year. Water balance: 74% actual evaporation (ET), 5% groundwater recharge, 21% surface outflow.
  • Post-SWSC (1991–2020, excluding recharge wells): Average annual precipitation 174.9 mm/year. Water balance: 82% ET, 5% groundwater recharge, 13% surface outflow.
  • Post-SWSC (1991–2020, including recharge wells): Groundwater recharge increased to 7.2% of total precipitation.
• Impact of WHTs on Recharge (Koutine watershed):
  • SWAT-simulated recharge (with WHTs) averaged 19.6 mm/year (10% of mean annual precipitation 195.5 mm/year).
  • Transmission losses (indirect recharge through wadi beds) averaged 55 mm/year (28% of precipitation).
  • A scenario without WHTs showed recharge dropping to 5% of precipitation, indicating WHTs contributed an additional 5% recharge.
  • HRUs under OLVP (tabias) and OLVM (jessour) land uses exhibited high recharge rates of 161% and 119% of precipitation, respectively, due to runoff concentration.
• Recharge from Recharge Wells: Average simulated flux was 99,396 m³/year per well, translating to an additional 4 mm/year of recharge at the aquifer scale.
• Runoff Correlation: Strong correlation (R² = 0.76) between SWAT-simulated surface runoff and empirical estimates using Fersi’s (1979) formula.

Contributions

• First quantitative assessment in Tunisia of the combined contribution of traditional (Jessour, Tabias) and modern (gabions, recharge wells) Managed Aquifer Recharge (MAR) systems to groundwater recharge under arid conditions using a process-based, spatially distributed SWAT model.
• Demonstrated the exceptional capacity of traditional Water Harvesting Techniques (WHTs) to concentrate and infiltrate runoff, significantly enhancing groundwater recharge beyond direct rainfall inputs.
• Provided a robust methodological framework for assessing MAR effectiveness in data-scarce arid and semi-arid regions, applicable for integrated water resource management and transferable to other North African and Sahelian contexts.
• Offered concrete quantitative insights for decision-makers to optimize MAR systems and allocate resources efficiently for sustainable water management and climate change adaptation.

Funding

• PRIMA project (SALAM-MED) from the European Union’s Horizon 2020 Research and Innovation Program: no. 2131.
• Arid Regions Institute of Medenine IRA, Tunisia (Laboratory of Eremology and Combating Desertification: LR16IRA01).

Citation

@article{Hadded2025Enhancing,
  author = {Hadded, Rym and Zaied, Mongi Ben and Castelli, Giulio and Abdelli, Fethi and Essifi, Bouajila and Bresci, Elena and Ouessar, Mohamed},
  title = {Enhancing groundwater resources through managed aquifer recharge: A SWAT application in arid southeastern Tunisia},
  journal = {Journal of Hydrology Regional Studies},
  year = {2025},
  doi = {10.1016/j.ejrh.2025.103027},
  url = {https://doi.org/10.1016/j.ejrh.2025.103027}
}