The hydrologic response in a hilly-gully catchment with a developed check-dam system on the Loess Plateau, China

Abstract:

Check-dam systems have been the most widespread and effective engineering structures for conserving water and soil in the Loess Plateau in the recent 30 years. Hydrologic response in Wangmaogou, a representative small catchment with 7 different kinds of land use types and 22 existing check dams (including newly-built, partial-destroyed, fully-deposited) in the Loess Plateau, is investigated via field data analysis and numerical simulation. Field data collected in this study include rainfall, discharge, and saturated soil hydraulic conductivity and soil water content and soil water characteristic curves at different depths, and surface water depth in front of check-dams during extreme rainfall events. A physics-based distributed model, the Integrated Hydrology Model (InHM) is employed to execute both seasonal rainfall-SWC (soil water content) simulation and event based rainfall-runoff simulation. Validation results show that InHM simulated SWC matches well with the measured SWC in the 18 TDR burial spots and it can successfully grasp extreme low discharge at the outlet of the catchment when most of the rainwater is blocked by the dam system. The study leads to the following results for the region: 1) the surface flow is dominated by the Horton overland flow occurring in most of the slopes covered by crusted grass; 2) the check dams built in the gullies can effectively prevent the valuable rainwater from running out of the catchment (about 90%) by terrain blocking and increasing infiltration of the sedimentary fields; 3) some nearly fully-deposited check-dams built on the end of the gully are under high risk of dam break during the extreme rainfall events because of the high water depth in front of the dam. The study confirms the applicability of InHM in the Loess Plateau, and the results expand our understanding about the hydrologic response in check-dam systems.