δ2H and δ18O characteristics of deep soil water and its recharge patterns of the returned farmlands on the Loess Plateau of South Ningxia
Identifying soil water movement and groundwater potential recharge in deep vadose zone of different vegetation types is important for ensuring groundwater resource sustainability in semi-arid areas,particularly after the implementation of the Grain for Green project.In this study,four sample plots of forest grassland(LC),woodland(LD),grassland(CD),and farmland(NT)were selected in the south of Ningxia to analyze the variation of soil water characteristics(SWC,δ2H,δ18O and lc-excess).Soil water isotope profiles were utilized to estimate recharge rates by the tracer peak method.The results showed significant differences in SWC and δ18O among the four sample plots(P＜0.05),with minimal SWC and evapotranspiration observed in the NT,mainly influenced by vegetation cover and soil texture.The findings further revealed that soil water in the thick vadose zone experienced significant mixing during infiltrating,resulting in three parts from top to bottom:the shallow zone(0-4 m),middle zone(4-10 m),and deep zone(10-15 m).Significant differences in SWC and δ18O among the four sample plots were observed between the shallow and middle zones(P＜0.05),while no significant difference was found in the deep zone(P＞0.05)according to analysis of variance(ANOVA),indicating homogeneous consistency and stability of the deeper soil water among four sample plots.Furthermore,potential groundwater recharge in this study was primarily dominated by piston flow,with mean potential recharge rates of 21.7 mm/a,18.1 mm/a,22.3 mm/a,and 15.6 mm/a for LC,LD,CD and NT,respectively.In summary,our investigation sheds light on the influence of the Grain for Green project in the loess area on soil water movement and recharge rules in the deep vadose zone,providing valuable data support for the regulation of vegetation patterns and sustainable management of water resources in the loess area.
deep soil waterhydrogen and oxygen stable isotopessoil water movementLoess Plateau
万方数据
维普
