Regulation of secondary soil salinization in semi-arid regions: a simulation research in the Nanshantaizi area along the Silk Road, northwest China

The degradation of soil quality is a common issue in arid and semi-arid regions along the Silk Road. To provide effective measures for controlling secondary soil salinization in irrigated farmland, this article presents a research on the water balance and salt balance in the lowland of Nanshantaizi, northwest China. On the basis of the meteorological, hydrological and hydrogeological data, a 2D transient groundwater flow model was developed to analyze the response of groundwater level to various scenarios of controlling and regulating soil salinization. The results show that the shallow water depth causes strong evaporation, resulting in the accumulation of salt in the area, and is the main controlling factor of secondary soil salinization in the lowland. The effective drainage system in the lowland can efficiently reduce groundwater level and can discharge salt into the river, thus, alleviating the soil salinization in the lowland. The reduction of irrigation water requirement in the high plain as well as in the lowland can lead towards better control of soil salinization in the lowland. The canal leakage is the main source of recharge of groundwater in the lowland. However, the reduction of the canal leakage at the beginning of soil salinization regulation is not recommended, as the reduction of canal water leakage may significantly weaken the efficiency of the new drains to remove salts that have already previously accumulated in the soils of the lowland.