Modelling Shallow Groundwater Evaporation Rates from a Large Tank Experiment

Abstract A large tank (1.4 m x 4.0 1.3 m) filled with medium-coarse sand was employed to measure evaporation rates from shallow groundwater at controlled laboratory conditions, determine drivers and mechanisms. To monitor the level drawdown 12 piezometers were installed in a semi regular grid equipped high precision water level, temperature, electrical conductivity (EC) probes. In each piezometer, 6 micro sampling ports every 10 cm capture vertical salinity gradients. Moreover, soil content, temperature EC measured unsaturated zone using TDR probes placed 5, 20 40 depth. The monitoring started February 2020 lasted for 4 months until became residual. model heads, variations SEAWAT employed. calibrated then used obtain unknown parameters, such as: maximum (1.5-4.4 mm/d), extinction depth (0.90 m), mineral dissolution (5.0e -9 g/d) concentration (0.35 g/L). Despite uniformly distributed, increase of rather uneven, while mimicked atmospheric increase. initial small changes rate evapoconcentration process groundwater, effective porosity most sensitive parameter. This study demonstrates that sandy soils can produce homogeneous table but appreciable differences distribution salinity.