[Objective] The ancient water storage and irrigation system in Sakya, Xizang autonomous region, listed in 2021 as a World Heritage Irrigation Structure, is a unique paradigm of high-altitude water resource management and an important testament to the diverse cultural heritage of the Chinese nation. Despite its profound value, existing research remains fragmented, and systematic studies from the perspective of water cultural heritage are particularly scarce. This study aims to fill this gap. [Methods] This study adopted a multidisciplinary approach integrating historical document analysis, field investigation, scientific principle verification, and value evaluation. First, classical Xizang texts, including Mkhas pa’i dga’ston and Rgyal rabs gsal ba’i me long, were examined to clarify the development stages and management traditions of the irrigation system. Second, field surveys were conducted to map the engineering structures (e.g., diversion weirs, reservoirs, and sluices) and to verify the current operation of the “Cuoben-Shuinv-Humin” management mechanism. Third, quantitative analysis was conducted to verify the scientific rationality of the system based on modern engineering theories such as the Bernoulli equation (potential energy conversion), Fourier’s law (thermal insulation and freeze protection), and hydraulic mechanics (pressure reduction principles). Finally, a comprehensive value evaluation framework was established, integrating theories from cultural heritage studies, ecological economics, and water resource management to systematically analyze the system’s tangible and intangible cultural heritage values. [Results] The development of the Sakya irrigation system experienced four key stages: 1) embryonic irrigation stage driven by nature worship during the Tubo period, 2) large-scale construction stage promoted by the integrated political and religious system in the Mongol-Yuan period, 3) stage of institutional innovation (e.g., a primitive “river chief system”) and ecological adaptation during the Ming-Qing dynasties, and 4) contemporary stage integrating traditional wisdom with modern technology. In terms of engineering structure, the system adopted a sophisticated “single-source, three-reservoir, sluice-regulated diversion” design, fully utilizing the local terrain for gravity-driven water conveyance without external energy input. The reservoirs were predominantly open earth-stone structures with capacities ranging from 30 000 m³ to 50 000 m³, reasonably arranged along the Chongqu River and composed of four core components: diversion weirs, channels or pipelines, reservoir bodies, and outlet pipe networks. Quantitative analysis verified three major scientific adaptations of the system to the plateau environment. (1) Efficient potential energy conversion: Utilizing a terrain height difference of 30-80 m, the system achieved an energy utilization efficiency exceeding 95%, and the head loss calculated using the Manning equation accounted for only 3.6% of the total head, which was sufficient to meet the irrigation demand of 100 000 mu (approximately 6 667 hectares) of highland barley fields. (2) Implicit application of pressure-reduction pool principles: The three-stage reservoir cascade reduced water pressure by 67% and channel scouring force by 96%, effectively preventing erosion of the earth-stone channels. (3) Thermal insulation and freeze protection design: Compared with pure stone structures, the composite structure of mortar-masonry stone and local clay reduced winter heat loss by 60% and lowered frost-heave risks by 80%, while reducing summer water evaporation by 60%, adapting to the plateau's extreme sub-frigid climate with winter temperatures as low as -25 ℃. The system demonstrated multidimensional values. (1) Political value: It provided the material foundation for Sakya to become the political and religious center of Xizang during the Mongol-Yuan period and promoted profound regional socio-economic transformation. (2) Economic value: More than 400 reservoirs currently in operation irrigate 40% of the highland barley cultivation area in Xizang, supporting Shigatse in becoming the “World Highland Barley Hometown”. (3) Cultural value: It integrates Xizang Buddhism, folk customs (e.g., rain-prayer rituals), and literary works (e.g., metaphors in Sa skya legs bshad), serving as a living carrier of water culture and a national water education base. (4) Ecological value: By using local materials and adapting to the terrain, the system minimized environmental disturbance while performing functions of flood regulation and groundwater recharge, embodying the ancient ecological wisdom of “harmony between human and nature”. [Conclusion] This study is the first systematic investigation of the Sakya irrigation system from the perspective of water cultural heritage, innovatively integrating traditional engineering practices with modern scientific principles and verifying the rationality of ancient high-altitude water resource management. The results demonstrate that the system is not only an engineering marvel, but also a living cultural-ecological system integrating physical structures, intangible management systems, and ecological ethics. Its multidimensional values highlight the diversity of Chinese water civilization and provide valuable reference for water resource management in high-altitude regions worldwide. To ensure the sustainable development of the system, targeted strategies are proposed: enhancing value interpretation through digital technologies, adopting holistic protection concepts such as “cultural routes”, implementing classified and phased protection mechanisms, and promoting the integrated development of culture and tourism. Through coordinated collaboration among government, communities, and academia, the Sakya irrigation system can be transformed from a static engineering heritage into a dynamic cultural-ecological entity, providing a model for the protection and development of global irrigation heritage and promoting the innovative development of plateau water culture.