Groundwater-lake interactions in a dune field system and their implications in the hydrochemical variability: Assessing the role of vegetation in groundwater recharge

Abstract

Lakes are critical components of hydrological and biogeochemical processes, particularly in semi-arid regions where their stability is essential for local ecosystems and settlers. However, in the current global change scenario, lake systems in arid and semiarid regions face significant alterations from climate change and land-use changes, threatening their water balance and quality. This study investigates the hydrochemical and isotopic characteristics of two shallow lakes (Los Pocitos and Nassau) located in a semiarid Dune Field in the Dry Pampa Plain of Argentina, with a focus on understanding how dune vegetation influences water balance and groundwater contributions. Both lakes are subsaline and alkaline with oversaturation in Ca2+ and Mg2+ carbonates, suggesting the precipitation of calcite and related evaporites and undersaturation of gypsum and sodium carbonates. Despite similar climatic and geomorphological settings, the lakes display contrasting salinities and groundwater inflow rates. The throughflow conditions (E/I = 0.55-0.62) prevent extreme salinity increases and lake desiccation, despite high evaporation rates. Isotopic mass balance modeling indicates a higher groundwater input in Lake Los Pocitos (∼16.6 cm month−1) than in Lake Nassau (∼1.0 cm month−1), likely associated with the presence of active unvegetated dunes that act as preferential local recharge areas sustaining fresh groundwater lenses that feed the lake. In contrast, the dense vegetation cover in dunes around Lake Nassau limits infiltration and reduces groundwater recharge. Our findings demonstrate that groundwater flow can sustain freshwater bodies in arid and semiarid environments and that lake evolution is controlled by an ecohydrological coupling between dune morphology, vegetation cover, and shallow groundwater circulation. This study highlights the importance of understanding lake-groundwater dynamics for the effective management of regions experiencing agricultural expansion and climate stress.