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.

With the rapid growth of the global demand for low-carbon energy, the development of hydropower has ushered in new development, but the ecological and environmental problems caused by this cannot be ignored. Taking the safe and efficient operation of water conservancy projects as the goal, this paper took the Maling Water Conservancy Project (MWCP) as an example to predict and evaluate the ecological environment risks of water conservancy projects. Based on the on-site geological surveys and experiments, the big well method and the long narrow horizontal tunnel method were used to estimate the water inflow from the underground caverns. The contaminant migration model was used to predict and analyze the groundwater quality. The impact of the MWCP on the surrounding environment was systematically analyzed and evaluated. The results showed that the estimated water inflow from the underground powerhouse and the water conveyance pipeline was about 7403.6 m³/d during the construction period. The groundwater level in the reservoir area could recover after a short drop, which had little effect on the surrounding vegetation. The groundwater quality was affected obviously because the migration speed of contaminants was very fast under abnormal conditions. During the operation period, it had little effect on groundwater level and had certain influence on groundwater flow field in local area. The source of sewage was mainly a small amount of domestic sewage, which could be ignored after taking anti-seepage measures. After storing water in the reservoir area, there was a possibility of small-scale immersion on the right bank. Most of the reservoirs had good stability conditions but the stability of the upper fault valley was poor; however, the possibility of leakage was very small. Overall, the project had little impact on the surrounding environment. The research results could also provide some references for other hydroelectric projects within the basin.

Based on the geological and hydrogeological conditions, and in situ hydrogeological tests of the emergency groundwater source in Nantong City, China, a 3D numerical model of the heterogeneous anisotropy in the study area was established and calibrated using data from pumping and recovery tests. The calibrated model was used to simulate and predict the water level of the depression cone during the emergency pumping and water level recovery. The results showed that after seven days of pumping, the water level in the center of the depression cone ranged from −51 m to −55 m, and compared with the initial water level, the water level dropped by 29 m to 32 m. The calculated water level has a small deviation compared with that of the analytical solution, which indicates the reliability and rationality of the numerical solution. Furthermore, during water level recovery, the water level of pumping wells and its surroundings rose rapidly, which was a difference of about 0.28 m from the initial water level after 30 days, indicating that the groundwater level had recovered to the state before pumping. Due to the emergency pumping time is not long, the water levels of Tonglu Canal, surrounding residential wells, and other aquifers will not be affected. After stopping pumping, the water level recovers quickly, so the change of water level in a short time will not lead to large land subsidence and has little impact on the surrounding environment.