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

一个装有中粗砂的大水箱 (1.4 mx 4.0 mx 1.3 m) 用于在受控的实验室条件下测量浅层地下水的蒸发率，以确定驱动因素和机制。为了监测地下水位下降，在半规则网格中安装了 12 个压力计，并配备了高精度水位、温度和电导率 (EC) 探头。在每个压力计中，每 10 厘米安装 6 个微型采样端口以捕获垂直盐度梯度。此外，使用放置在 5、20 和 40 厘米深度的 TDR 探头测量非饱和区的土壤含水量、温度和 EC。监测于 2020 年 2 月开始，持续了 4 个月，直到地下水下降成为残余。为了模拟地下水水头、温度和盐度变化，采用了 SEAWAT 4.0。^-9 g/d) 和蒸发浓度 (0.35 g/L)。尽管水位下降分布均匀，但地下水盐度的增加却相当不均匀，而温度的增加与大气温度的增加相似。地下水初始盐度和蒸发速率的微小变化控制着地下水的蒸发浓缩过程，而有效孔隙度是最敏感的参数。这项研究表明，沙质土壤的浅层地下水蒸发可以产生均匀的地下水位下降，但地下水盐度的分布存在明显差异。