TITLE:
Groundwater-Level and Thermal Dynamics Following Severe Drought: Insights from High-Frequency Monitoring in the Bekaa Valley, Lebanon
AUTHORS:
Ihab Jomaa, Simone Mereu, Matteo Funaro, Marta Debolini, Randa Massaad, Sleimen Skaf
KEYWORDS:
Carbonate Aquifer, Aquifer Memory, Groundwater Recharge, Irrigation Demand, Hydraulic Response, Groundwater Temperature, Telemetry Monitoring
JOURNAL NAME:
Journal of Water Resource and Protection,
Vol.18 No.10,
October
10,
2026
ABSTRACT: Groundwater resources are essential for agricultural sustainability in semi-arid regions, yet continuous empirical observations of deep aquifer dynamics remain scarce. This study addresses this empirical gap by presenting the first multi-year, high-frequency telemetry record of groundwater-level, thermal, and Total Dissolved Solids (TDS) dynamics from a dedicated 400 m unpumped observation borehole in Kfardane, Northern Bekaa Valley, Lebanon. A total of 2998 piezometric observations (6-hour logging intervals) collected between April 2024, and August 2026 were analyzed alongside daily precipitation, air temperature, and in-situ TDS data across two contrasting hydrological cycles following a severe drought. Results reveal pronounced seasonal drawdown driven by regional agricultural abstraction, reaching an absolute maximum water-table depth of 233.0 m b.g.l. in July 2025 following an anomalously dry wet season (126 mm rainfall). Conversely, a wetter 2025-2026 winter (311 mm precipitation) generated a robust 17.0 m hydraulic head recovery by April 2026 (216 m b.g.l.), buffering the aquifer against extreme stress during the subsequent 2026 irrigation season (summer drawdown reaching 227.2 m b.g.l.). Subsurface temperature remained stable overall (15.8˚C - 16.4˚C) despite surface air fluctuations exceeding 40˚C. Transient downhole cooling events (ΔT = −0.51˚C) coincided with rapid, concurrent drops in TDS (ΔTDS = −64.8 ppm) following peak winter precipitation and rapid mountain snowmelt. Overall, the findings demonstrate that seasonal groundwater stress in the deep Bekaa aquifer is governed by the interaction of irrigation pressure, precipitation variability, and multi-year antecedent storage memory (highlighting the importance of telemetry).