Abstract:

The groundwater is always polluted to some extent by pesticides and fertilizers. There are few researches on monitoring of groundwater in karst areas at present. This paper presents a case study on the Jiangjia spring in Qingmuguan karst valley experimental site,Chongqing, China. Rainfall and physico-chemical variations of groundwater are monitored by the HOBO weather station. The CTDP300 multi-parameter auto-recordable instrument and NITRATAX plus sc online NO^-₃-N analyzer are employed in different rainfall conditions at Qingmuguan karst valley. The results show that the karst dynamic system is very sensitive to the environment and responds promptly. The spring's pH value decrease, as it is diluted by the acid rain. The water temperature changes owing to rainfall, duration, and air temperature. Electrical conductivity changes with rainfall environment. The dilution function of the rainwater mainly occurres in the initial stage under normal rainfall environment and the crevasse watery medium plays a key role in the next stage.The chemical characteristics of water seepage is mainly controlled by the rainwater under rainstorm environment and the pipeline watery medium plays a key role. Positive correlation exists betweenNO^-₃ and electrical conductivity,and both of them are significantly correlated to the amount of rainfall. It indicates that the rainfall is a very important factor to contaminated groundwater, and can also result in the missing of the soil and nutrition element.The research of the underground river is important in solving residents potable water, conserving groundwater and preventing the soil from desertification.

Key words:  karst spring, hydro-physico-chemistry, environmental effect, ridge-trough area, east Sichuan