Land use change affects groundwater recharge in the Changwu Loess Tableland of China

Long-term soil water data monitored in deep loess profiles under different land use patterns, combined with the hydrogen and oxygen stable isotopic tracer techniques, were used to investigate the effects of land use change on groundwater recharge in the Changwu Loess Tableland. Results showed that: ① Both piston flow and preferential flow coexisted in the process of groundwater recharge. The land uses, in order of decreasing the groundwater recharge by piston flow, are the fallow land, low-yield filed and high-yield field. ② The increased productivity and large scale conversion of cropland to apple orchards have resulted in reduced groundwater recharge by piston flow, combined with the increased groundwater mining, causing the groundwater table to decline continuously at 0.3 m/a. ③ The isotopic data indicate that preferential flow is currently the main path way for groundwater recharge. In order to achieve effective supply and sustainable utilization of groundwater resources on the Loess Tableland, it is necessary to regulate the land use structure reasonably and maintain an appropriate level of land productivity.