Research on the Groundwater Recharge in Loess Plateau Based on Stable Isotopes

The typical loess plateau area- Changwu Plateau and the Wangdonggou small watershed on the edge of Changwu Plateau is select‐ed as the study area. The precipitation,soil water within the depth range of 0～15 m under different surface vegetation types,well water and spring water are selected. The composition characteristics of the stable isotopes of hydrogen and oxygen in each water body are compared and analyzed,and then the groundwater replenishment method in the loess plateau area is judged. The results show that:（1） The local atmospher‐ic precipitation line formula（LMWL）is δ~2H=7.38δ¹⁸O+4.75（R~2=0.94,n=60）,and the isotopic composition of precipitation and the deuteri‐um surplus shows a seasonal trend of decreasing first and then increasing. （2） The hydrogen and oxygen isotopes of soil water samples are dis‐tributed at the lower right area of LMWL,and the distribution is relatively discrete. The local soil water evaporation line（SWEL）is δ~2H =6.15 δ¹⁸O -13.78（R~2=0.79,n=178）. The soil water stability isotope changes in the 0～3.5 m soil layer are relatively drastic,while the lower layer changes in a wave-like manner with depth. The distribution of stable isotope soil water in the deep profile has a small abrupt change point,indicating that plug flow and preferential flow co-exist during the process of soil water infiltration. （3） Combined with an analysis of the hydrogen and oxygen stable isotopic characteristics of rainwater,soil water and groundwater,groundwater in the loess plateau area is mainly recharged by the dual infiltration of soil water through plug flow and preferential flow.