The response of regional groundwater system to irrigation at Heifangtai terrace, Gansu Province

The response of regional groundwater system is the basis for the research on landslides induced by irrigation. The Heifangtai terrace comprises three groundwater units of loess, gravel and sand-mud stone. Taking the loess unit as the study object, which affects the stability of loess slope most, the authors analyzed the changes of water balance in the loess unit before and after irrigation, recovered the evolution of groundwater system induced by irrigation and predicted the development trend of the groundwater system under the condition of different irrigation volumes with the numerical method. The calculated results show that the water balance has been broken and the original groundwater system has been changed after a long term irrigation in this area. The groundwater level in the center of the plateau has increased by 20m in the past 44 years, and it tends to decrease when the volume of irrigation is reduced to 350×104m3/a. The results obtained can provide scientific support for comprehensive prevention and control of geo-hazards in Heifangtai area.