Soil salinity accumulation and groundwater degradation due to overexploitation over recent 40-year period in Yaoba Oasis, China

Abstract

Yaoba Oasis is a traditional tillage farmland completely dependent on irrigation with groundwater. Previous investigations (1980–2015) have revealed that over-extraction of groundwater, deterioration of water quality, and soil salinization are the primary factors limiting the development of the regional agricultural economy. This study aimed to determine the impact of human activities, specifically groundwater exploitation and agricultural irrigation, on the migration of soil salinization since 1980 in the Yaoba Oasis. Specifically, water and soil samples were collected and analyzed from 90 wells and 21 soil sites. Results indicated that the groundwater level in the oasis has steadily declined at a rate of 0.04–0.59 m per year, primarily due to groundwater overexploitation. The annual average soil salt accumulation was approximately 91.1–155.2 mg/kg. Soil salinity was strongly correlated with the hydrochemical composition, with all indicators increasing along the flow path. Irrigation infiltration resulted in salt accumulation below 20 cm, with residual salts being leached by the irrigation return water. Overall, residual salt dissolution under flood irrigation and saltwater intrusion in desert salt lakes are the main reasons for soil salt accumulation and groundwater quality deterioration. To mitigate these issues and maintain the ecological balance of desert oases, it is imperative to limit the overexploitation of groundwater and reduce the amount of irrigation, thereby preventing groundwater contamination and soil salinization.