Geometry of the modelled freshwater/salt-water interface under variable-density-driven flow (Pétrola Lake, SE Spain)

Sanz, D.; Valiente, N.; Dountcheva, I.; Muñoz-Martín, A.; Cassiraga, E.; Gómez-Alday, J. J.

Geometry of the modelled freshwater/salt-water interface under variable-density-driven flow (Pétrola Lake, SE Spain) | Géométrie de l’interface eau salée–eau douce modélisée avec un écoulement à densité variable (lac Pétrola, SE Espagne) Modelado de la geometría de la interfase agua salada–agua dulce bajo condiciones de flujos de densidad variable (Lago de Pétrola, SE España) 西班牙东南部Pétrola湖变密度模拟的咸淡水界面几何形状 Geometria da interface modelada de água salgada–água doce sob fluxo dirigido por densidade variável (Lago Pétrola, SE Espanha)

2022

Pétrola Lake in southeast Spain is one of the most representative examples of hypersaline wetlands in southern Europe. The rich ecosystem and environmental importance of this lake are closely associated with the hydrogeological behaviour of the system. The wetland is fed by the underlying aquifer with relatively fresh groundwater—1 g L⁻¹ of total dissolved solids (TDS)—with a centripetal direction towards the wetland. In addition, the high evaporation rates of the region promote an increase in the concentration of salts in the lake water, occasionally higher than 80 g L⁻¹ TDS. The density difference between the superficial lake water and the regional groundwater can reach up to 0.25 g cm⁻³, causing gravitational instability and density-driven flow (DDF) under the lake bottom. The objective of this study was to gain an understanding of the geometry of the freshwater–saltwater interface by means of two-dimensional mathematical modelling and geophysical-resistivity-profile surveys. The magnitude and direction of mixed convective flows, generated by DDF, support the hypothesis that the autochthonous reactive organic matter produced in the lake by biomass can be transported effectively towards the freshwater–saltwater interface areas (e.g. springs in the lake edge), where previous research described biogeochemical processes of natural attenuation of nitrate pollution.

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