Geometry of the modelled freshwater/salt-water interface under variable-density-driven flow (Pétrola Lake, SE Spain)
2022
Sanz Martínez, David | Valiente Parra, Nicolás | Dountcheva, Iordanka | Muñoz Martín, A. | Cassiraga, E. | Gómez Alday, Juan José
Pétrola Lake in southeast Spain is one of the most representative examples of hypersaline wetlands in southern Europe. The richecosystem 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—1gL-1of total dissolved solids (TDS)—with acentripetal direction towards the wetland. In addition, the high evaporation rates of the region promote an increase in theconcentration of salts in the lake water, occasionally higher than 80 g L-1TDS. The density difference between the superficiallake 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 mag-nitude and direction of mixed convective flows, generated by DDF, support the hypothesis that the autochthonous reactiveorganic 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 nitratepollution
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