Simulation of Groundwater Flow in Fractured-Karst Aquifer with a Coupled Model in Maling Reservoir, China

Jinbang Cai,Yue Su,Yong Huang,Huan Shen

doi:10.3390/app11041888

Abstract

A coupled model has been developed to simulate groundwater flow in fractured karst systems according to the complex geological and karst hydrogeological conditions of the dam site, where a 3D mathematical model based on Boussinesq equation was used to describe the movement of groundwater flow in fractured medium, and a 1D conduit model for karst medium. The model was solved with the continuous hydraulic heads at the common boundaries. The hydraulic conductivities of karst medium were determined by geometrical parameters and flux of pipes. Furthermore, the permeability parameters for fractured medium were calibrated by the measured and calculated groundwater levels. The calibrated model was employed to predict the variation of groundwater flow field and leakage from the karst pipes and underground powerhouse during the reservoir operation. The simulated results showed that the groundwater level of the powerhouse had decreased by about 2–5 m. The water level of conveyance pipeline had risen by 10–20 m, and the water level on both banks had risen by 15–25 m. The leakage of karst conduits for impervious failure was larger than that for normal seepage control. In addition, the leakage of the powerhouse was estimated to be about 1000–3000 m3/d, and the seepage control of karst pipes had little influence on the leakage of underground powerhouse.

Highlights

Many water conservancy and hydropower projects are located in fractured karst areas.The existence of karst pipes is a serious threat to the normal storage of reservoirs
A 3D mathematical model is employed to describe the movement of groundwater flow in fractured medium and a conduit model is used to describe it in karst medium
The permeability of karst pipes was larger along the development direction of pipes

Summary

Introduction

The existence of karst pipes is a serious threat to the normal storage of reservoirs. Micro-fissures, and mesoscale fissures often account for the main part of the porosity of karst media, but their permeabilities are far less than those of karst pipes and faults. These pores or fractures play a major role in water storage, where groundwater flow follows Darcy’s law. Karst pipes play a role in water conduction in the movement of groundwater; the groundwater flow follows non-Darcy’s law or non-linear flow owing to faster flow velocity [6,7,8,9]

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Conclusion