Effects of precipitation, irrigation, and exploitation on groundwater geochemical evolution in the people’s victory canal irrigation area, China

Abstract

The People's Victory Canal Irrigation Area is a large gravity irrigation area in the middle and lower reaches of the Yellow River. Groundwater hydrochemistry is controlled by geochemical weathering, precipitation, irrigation from the Yellow River diversion, and artificial exploitation. The Piper diagram, hierarchical cluster analysis, Gibbs diagram, and ion proportion coefficient were applied to improve our understanding of the hydrogeochemical evolution. Our results indicated that groundwater ion concentration has prominent spatial zonation characteristics in the study area. The groundwater ion components in the low salinity area are mainly a result of silicate and carbonate weathering, with the major hydrochemical type being HCO3·Cl–Na·Mg and HCO3–Na·Ca. The soil salt content in the low salinity area is low. The main effect of precipitation on groundwater chemical composition is a reduction in groundwater ion concentration by recharge. The groundwater ion concentration near the canal is similar to the Yellow River water. The groundwater ionic components in the high salinity area are mainly affected by weathering, silicate dissolution, and evaporative salt rocks. The water chemical type is SO4·Cl–Na·Mg. Expectedly, the soil salt content is high in the high salinity area. The Yellow River recharge decreased the ion concentration of groundwater near the canal. In addition, the groundwater exploitation increase results in a change in the flow field, affecting the local groundwater chemistry. The groundwater ion concentration increases as the groundwater flow from the high salinity area to the low salinity area. In contrast, the groundwater ion concentration in the high salinity area decreases. We further discuss these results in the context of the complex influence of precipitation, Yellow River diversion irrigation, and artificial exploitation on the hydrogeochemical evolution.