Isotope-Enhanced Ecohydrological Modeling of Snow-Driven Recharge in Semi-Arid Mountains

This study investigates the dynamic behavior of snow in semi-arid mountainous landscapes, emphasizing the use of the isotope signal as a tool for tracing hydrological processes. Thin snowpack poses a significant challenge, leading to extensive shifts in isotope values and complicating the estimation of catchment-average snowpack signatures. Traditional mixing models fall short in such scenarios, necessitating detailed approaches involving sampling along the hydrological pathway. The research employs a tracer-enabled spatially-distributed, process-based ecohydrological modeling approach to evaluate groundwater recharge processes in the complex settings of a regional watershed in the Middle Atlas mountains of Morocco. The study's objectives are to quantify recharge rates and dynamics seasonal variations, conducting a comparative analysis of yearly to sub-seasonal trends dating from 2017 onwards, and exploring stable isotope dynamics in snow-fed compartments of the hydrological cycle. The preliminary results of the ecohydrological simulations are discussed ; the simulated streamflow exceeds observed values, attributed to factors such as low winter evapotranspiration and the generalized spatialization of parameters. Variations in water table levels of each aquifer, and evapotranspiration data reveal a time lag influenced by seasonal variations and vegetation density. Stable isotopes closely mirror observed data, indicating the model's capability to capture the dynamic behavior of the aquifer system, with spatialized maps revealing a time delay between peak SWE (Snow Water Equivalent) abundance and isotopic depletion. Recharge dynamics are notably influenced by Triassic clay formations, with higher rates in exceptionally wet years and variations based on geological properties. The study highlights the important role of SWE in groundwater recharge, with peak SWE coinciding with major recharge events, and decreasing SWE contributing to groundwater depletion.

Keywords: Recharge, snowpack, isotope, ech2o-iso, snowmelt.