Assessing groundwater-surface water interactions in shallow lakes under anthropogenic stress (Pampa plain, South America): A hydrochemical and isotopic approach

MARTIN, MARIA EUGENIA; CAMPODONICO, VERENA AGUSTINA; LECOMTE, KARINA LETICIA; PASQUINI, ANDREA INÉS

Groundwater for Sustainable Development

Elsevier

Año: 2025 vol. 30

2352-801X

Human interventions, such as land conversion, climate change, and water use, are significantly impacting the global water cycle. Lakes and wetlands, which are the most abundant inland water bodies, are particularly affected. The Argentine Pampa plain, one of the largest plains worldwide, contains numerous temporary and permanent shallow lakes. This study assessed the impacts of anthropic interventions on the hydrological dynamics and surface water-groundwater interactions of artificially connected shallow lakes in the Southern Pampa plain (La Chanchera-La Brava system). Major ion chemistry and stable isotopic analysis were used, along with δ18O mass balance calculations to quantify the groundwater inflow. A small unconnected lake (Médano de Castro lake) was also analyzed. The canal-connected lakes and associated groundwater are alkaline and brackish, with a sodium-chloride/sodium-non-dominant composition. Isotopic modeling reveals that these lakes receive groundwater input year-round, with inflow about seven times higher in the wet season due to rising water tables. In contrast, the unconnected lake, with sodium-bicarbonate waters, shows doubled salinity in the wet season due to evaporation. Its hydrochemistry reflects the input from local groundwater from the surrounding dune system, which prevents desiccation. All lakes are throughflow systems with short water residence times (< 1 year), indicating a constant water exchange. This study emphasizes the importance of understanding lake-groundwater dynamics in regions facing agricultural expansion and climatic pressures.