Study on characteristics of groundwater runoff in heterogeneous karst water-bearing medium in karst mountain area of Guizhou Province
There are heterogeneous karst groundwater mainly limestone and homogeneous karst groundwater mainly dolo-mite in karst mountainous areas of Guizhou Province.Heterogeneous karst groundwater is characterized by isolated karst devel-opment,extremely uneven occurrence and distribution,large underground water volume but large dynamic variation,difficult exploitation of groundwater resources,fragile groundwater environment,etc.,which affects the normal drinking water of resi-dents in the area and restricts economic and social development.Taking an underground river system in northeast Guizhou Province as the research target area,in order to study the groundwater runoff characteristics of this underground river system,five connectivity tests and one group hole pumping test were carried out in the study area to analyze the spatial and temporal distribution characteristics of groundwater runoff direction,runoff type,runoff dynamics,runoff velocity,flow pattern and flow line of the underground river system.Contrast the difference of groundwater runoff characteristics in homogeneous karst water-bearing medium.The results show that the four sinkholes(drop points)in the study area all discharge from the underground river outlet No.S1 in the southwest,which proves that the direction of groundwater runoff in the area has the coexistence of rising and falling and the concentration of underground river pipelines;The types of groundwater runoff in the area are mainly karst cave-pipeline,centralized runoff,supplemented by small-scale,lateral branch pipeline recharge,and slow flow phe-nomenon exists in local faults;The dynamic instability of groundwater runoff and the seasonality of"quick recharge and quick discharge"are significant;The groundwater flow line in the area also has a U-shaped feature of irregular rise and fall,which leads to the drilling in the area to reveal that the buried depth of the groundwater level is greater than the static water level,and the vertical groundwater has pressure.Karst development in limestone area of underground river system is not uniform,which results in great difference and significant contrast between groundwater runoff characteristics and uniform karst water-bearing medium in runoff direction,runoff type,flow velocity,dynamic and flow line.The results can provide reference for groundwa-ter development and protection in Guizhou karst mountain area.
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