Vegetation coverage change and erosion types impacts on the water chemistry in western China

Exploring the characteristics of water chemistry under different vegetation coverage and erosion types is important for water resource utilization and ecological environmental protection. After investigating the water chemistry of the surface water and groundwater in Xinjiang and Tibet in western China, this study revealed the response of hydrochemistry to vegetation coverage and erosion types. The results showed that different ions have different responses to the NDVI (normalized difference vegetation index). Sodium (Na⁺) in the surface water and groundwater was negatively correlated with the NDVI, while magnesium (Mg²⁺) and bicarbonate (HCO₃^-) experienced no significant changes with vegetation. Moreover, potassium (K⁺) in the surface water was positively correlated with vegetation, while that in the groundwater was negatively correlated with vegetation. Furthermore, calcium (Ca²⁺) and nitrate (NO₃^-) in the surface water were negatively correlated with the NDVI, but the groundwater experienced no evident change. In addition, chlorine (Cl^-) and sulfate (SO₄^2-) in the groundwater were negatively correlated with the NDVI, but these indexes in the surface water had no evident variation trend. In addition, different erosion types have different effects on hydrochemistry. Assuming the same amount of erosion occurs, wind erosion has the greatest effect on hydrochemistry, followed by hydraulic erosion, and freeze-thaw erosion has the least effect. The results of this study can help improve our knowledge of water evolution and the relationship between hydrochemistry and vegetation coverage and erosion types, promote effective management of water resources and provide a new direction for water research.