Effects of Groundwater with Various Salinities on Evaporation and Redistribution of Water and Salt in Saline-sodic Soils in Songnen Plain, Northeast China

Groundwater mineralization is one of the main factors affecting the transport of soil water and salt in saline-sodic areas. To investigate the effects of groundwater with different levels of salinity on evaporation and distributions of soil water and salt in Songnen Plain, Northeast China, five levels of groundwater sodium adsorption ration of water (SARw) and total salt content (TSC mmol/L) were conducted in an oil column lysimeters. The five treated groundwater labeled as ST0: 0, ST0: 10, ST5: 40, ST10: 70 and ST20: 100, were prepared with NaCl and CaCl₂ in proportion, respectively. The results showed the groundwater evaporation (GWE) and soil evaporation (SE) increased firstly and then decreased with the increase of groundwater salinity. The values of GWE and SE in ST10: 70 treatment were the highest, which were 2.09 and 1.84 times the values in the ST0: 0 treatment with the lowest GWE and SE. There was a positive linear correlation between GWE and the Ca²⁺ content in groundwater, with R² = 0.998. The soil water content (SWC) of ST0: 0 treatment was significantly (P < 0.05) less than those of other treatments during the test. The SWC of the ST0: 0 and ST0: 10 treatments increased with the increase of soil depth, while the other treatments showed the opposite trend. Statistical analysis indicated the SWC in the 0–60 cm soil layer was positively correlated with the groundwater TSC and its ion contents during the test. Salt accumulation occurred in the topsoil and the salt accumulation in the 0–20 cm soil layer was significantly (P < 0.05) greater than that in the subsoil. This study revealed the effects of the salinity level of groundwater, especially the Ca²⁺ content and TSC of groundwater, on the GWE and distributions of soil water and salt, which provided important support for the prevention and reclamation of soil salinization and sodificaton in shallow groundwater regions.