Abstract:

In order to simulate the groundwater movement in the karst area more accurately, a karst hydrogeological unit in Pu’an County, southwest Guizhou Province was taken as the research area. The FEFLOW software based on the finite element method was employed to establish a numerical simulation model that couples karst conduits with equivalent porous media for groundwater flow in the area. Gaussian random distribution was employed to generate conduits for underground rivers controlled by the geological conditions such as fault, fissure, fracture etc. The water flow in the equivalent porous medium was described by the partial differential equation of the 3-D transient flow, and the water flow in the conduit was described by the Manning-Strickler equation. The water conducting fault is treated as a strong permeable block, the infiltration coefficient of rainfall in the catchment areas of the sinkhole is set to 1, and the spring is treated as a pumping well with a constant head in the numerical model. The simulation results showed that the determining coefficient of the relationship between the calculated water level and the measured water level at 25 observation wells can reach 0.998 5, and the Nash-Sutcliffe efficiency coefficient reaches 0.998 2, which is very close to 1. It shows that the groundwater simulation model based on these treatments reflects the characteristics of karst groundwater movement and has strong simulation ability, which can be used to improve the evaluation accuracy of karst groundwater resources.

Key words: karstic groundwater, underground river, FEFLOW, groundwater numerical simulation, Gaussian distribution