Effects of agricultural activities on hydrochemistry in the Shiyang River Basin, China.

Agricultural water accounts for more than 80% of the available water in arid areas. Agricultural activities have a great impact on surface water and groundwater. If the impact of agricultural activities on hydrochemistry is not prevented, the risk of water quality change in arid areas may be greatly intensified. Based on the hydrochemical data of the whole Shiyang River Basin from April 2014 to October 2019, this paper analyzes the impact of agricultural activities on hydrochemistry in the basin. The results show that (i) in the middle and lower reaches of farmland with high intensity of agricultural activities, the ion concentration of groundwater in summer and autumn is significantly higher than that in winter and spring due to the influence of irrigation; (ii) the runoff ion concentration in the backflow of the river reaches recharged by irrigation water is significantly higher than that of other reaches; (iii) due to strong evaporation, different types of reservoirs will lead to an overall increase in ion concentration, which is more obvious in plain reservoirs and river tail lakes. In addition, the reservoirs have a certain removal effect on nitrates.

Ion migration process and influencing factors in inland river basin of arid area in China: a case study of Shiyang River Basin.

A thorough understanding of the processes and driving factors of ion migration, dilution, and enrichment in arid inland river basins is the basis for implementing water resources management. In this study, we analyzed the water chemistry of streamflow, groundwater, and precipitation and the behavior of main elements in the Shiyang River Basin by means of the hydrochemical diagram and multivariate statistical analysis. The spatial variation of water chemistry was obvious, and the conversion between different water bodies was frequent. The ions migrated from the mountain area to the oasis and desert and accumulated near the terminal lake finally. There were obvious differences in hydrochemistry between surface water and groundwater. From the mountain to the basin, the hydrochemical type of surfer water has varied, and the hydrochemical type of groundwater has changed from Ca-Cl type to Na-Cl type. The hydrochemistry of the basin was controlled by silicate weathering. However, the influence of water-rock interaction on surface water and groundwater was different, and the surface water was more complex. Significantly, agricultural activities and sewage discharge had a negative impact on the water environment. Interbasin water transfer (IBWT) was a form of external ions input from outside the basin, which affected the chemical characteristics of surface water in the lower reaches to a certain extent. In arid areas, human impact on water chemistry needs to be paid attention. These results are helpful to strengthen the understanding of the relationship between different regions and different water bodies in the arid basin.