Precipitation recharges the shallow groundwater of check dams in the loessial hilly and gully region of China

Check dams affect regional hydrological cycles and ecological environments. We conducted a field monitoring experiment in the Liudaogou Catchment on the Loess Plateau in China to determine the spatiotemporal response of shallow groundwater recharge and base flow by precipitation in check dams of this loessial hilly and gully region. The amount and seasonal distribution of precipitation directly affected the changes in shallow groundwater and base flow. The shallow groundwater was recharged by in situ vertical infiltration and lateral underground movement. Precipitation >30.0 mm d −1 recharged the shallow groundwater by piston flow when the water table in the check dam was <4.0 m. When the water table varied from the head (>4.0 m) to the middle and tail (<4.0 m) of the check dam, the influx of precipitation was by runoff in the catchment above the trench head, replenishing the groundwater vertically through the trench head and then moving laterally underground to the end of the dam. The response of the base flow and groundwater lagged the precipitation by a certain period. The lag time of the base flow was about 5–16 days, in which the response was more sensitive than for shallow groundwater. The lag time of the vertical supply for the response of the precipitation to the shallow groundwater was about 12–54 days, whereas the lag time for the lateral supply was about 72–93 days. The lag time may be associated with precipitation, temperature, solar radiation, vegetation water consumption and soil porosity. These findings will help elucidate the processes of groundwater recharge and provide new insight for managing the water balance in this loessial hilly and gully region.