Abstract: To address the challenges posed by multi-source heterogeneous data, coexisting multi-precision levels, and large data volumes in 3D scene construction for hydropower projects, as well as the inability of single construction methods and graphic engines to meet the demands of multi-level, multi-precision 3D digital applications, this paper proposes a hierarchical and categorized approach to constructing 3D scenes for hydropower projects. The approach is guided by application requirements and integrates the characteristics of Unreal Engine, Unity 3D, BIM, GIS, and other technologies. The paper thoroughly explores technical routes for integrating multi-source 3D data. Based on this, it develops scene application solutions centered around different 3D graphic engines. By analyzing the digital scene presentation features of various types of 3D graphic engines, the paper introduces an adaptive fusion method for multiple graphic engines. This achieves lightweight and efficient 3D scene construction and application, effectively resolving the difficulties in full-scene 3D digital applications for hydropower projects. Engineering applications demonstrate that this method significantly enhances the practicality and interactivity of digital models, improves the efficiency of 3D scene scheduling and rendering, and provides a technical support for the development of smart hydropower systems.