Study on hydrologic regime of underground river in typical karst valley——A case study on the Qingmuguan subterranean stream in Chongqing

In order to grasp the hydrologic regime of underground river,a case study on the Qingmuguan subterranean stream in Chongqing was carried out.During May 2007 to June 2008,a water table gauge(WGZ-1 photoelectric figure fluviograph monitor)and water quality monitoring site were set up to record the water level,temperature,pH and conductivity.Hydrology dynamic method was adopted to analyze the response of hydrologic dynamic of the subterranean stream to the rainfall in this paper.The result showed,during the rainfall,water table and discharge increased with the rain,especially on July 17,2007,some peaks appeared in the large storm,the highest water level was 1.175 m,and the response lagged for 6 h10 min after the largest rainfall intensity with the highest discharge being 2.578 1 m3/s and the smallest only 0.018 9 m3/s.It was found that there was a significant correlation between the water table regime and rainfall event,which indicated the Qingmuguan subterranean stream is developed intensity in tensity with single conduit and weak water-storing ability.Conductivity.pH and water temperature also responded to the rainstorm rapidly.Conductivity fell down from 602.7 to 462.09 μs/cm,pH fell down from 7.23 to 7.01,and water temperature risen from 18.9 ℃ to 19.5 ℃,all these indexes lagged shorter than 15 hours.