In wetland ecosystems, the soil–water environment formed by the interaction of surface water, soil, and groundwater plays a crucial role. It is the main factor affecting wetland vegetation types, root distribution, and water utilization strategies. Among these factors, groundwater depth is even more critical. This study employed high-density electrical methods to conduct long-term monitoring of groundwater levels in the tunnel construction area, aiming to thoroughly investigate the effects of the Hanjiang-to-Weihe Water Diversion Project (HWWDP) on the groundwater environment of wetlands. Practice has shown that high-density electrical method monitoring points are flexible, adaptable to various terrains and engineering environments, and effective for groundwater exploration. They accurately track groundwater level changes and enable continuous monitoring. The monitoring results show that although the tunnel construction of the HWWDP has a certain impact on the groundwater level of wetlands, the impact is relatively small and the overall variation range of the water level is not large. This indicates that the HWWDP has taken certain measures during the construction process to reduce interference to the groundwater environment of wetlands. However, it is still necessary to continuously pay attention to the potential impact of the project on the groundwater environment of wetlands, further optimize the construction plan and take more effective protection measures to ensure the stability and sustainable development of wetland ecosystems.