Abstract: In the current development of intelligent construction informatization in hydraulic engineering, the knowledge fusion and efficient utilization of multimodal data have become key industry challenges. Knowledge graphs, by providing structured representations of hydraulic entities and their complex relationships, offer novel solutions for engineering management and risk decision-making. This paper systematically analyzes research progress in knowledge graphs for hydraulic engineering: First, it elaborates on the construction process of hydraulic engineering knowledge graphs, summarizing key technologies involved from three core dimensions - knowledge extraction, knowledge fusion, and knowledge reasoning. Second, it examines the current application status of both knowledge graphs and large language models in hydraulic engineering, while providing a comprehensive analysis of their synergistic symbiotic models and related research. Finally, the paper concludes with a summary and outlook on future development trends of knowledge graph applications in hydraulic engineering.