Abstract:
Surface water and groundwater interaction is very complex and cannot be ignored in engineering geology and hydrogeology. In recent years,the technology of studying the surface water and groundwater interaction based on the temperature tracing method has been developed rapidly. Among them,Distributed Temperature Sensing(DTS)technology is a reliable method to obtain both temporal and spatial continuous temperature information. In order to study surface water and groundwater interaction at different depths by DTS,this study conducted two pumping tests(water level drops of 0.75 m and 7.2 m,respectively)in a hydrological well in Taibai Island,Yangtze River,and the temperature response of strata at different depths was measured by DTS. The surface water and groundwater interaction processes under different pumping conditions were finely observed. The results indicated that: (1)DTS technology can accurately identify the surface water and groundwater interaction intensity under different hydraulic conditions and reflect complex hydraulic changes.(2)The change of groundwater temperature during the surface water and groundwater interaction is affected by both the interaction intensity and the surface water temperature. Taking the small depth pumping as an example,the interaction intensity increased in the initial stage of pumping,and the surface water temperature rise rate was 0.6 ℃·h
-1,and the groundwater temperature rise rate in the warming zone was 0.8 ℃·h
-1. The interaction intensity was stable in the medium stage of pumping,and the surface water temperature rise rate was 0.4 ℃·h
-1,while the groundwater temperature increased at a rate of only 0.2 ℃·h
-1. After the pumping,the groundwater temperature continuously rose although the interaction intensity was weakened.(3)The surface water and groundwater interaction intensity inversely correlates with the stratum depth: the surface water and groundwater seepage path length determines the interaction intensity. The shorter the seepage path,the higher the interaction intensity. This study indicated that the temperature tracing method based on DTS technology can effectively observe the surface water and groundwater interaction at different depths and initially quantify the interaction intensity,so as to provide technical support for in-depth study of the surface water and groundwater interaction,disaster prevention,and mitigation in engineering geology.