Abstract: As the "Roof of the World" and the "Water Tower of Asia", the Qinghai-Tibet Plateau is the third-largest freshwater reservoir globally, supporting nearly 2 billion people across 9 countries and playing a pivotal role in safeguarding Asia's water security and ecological stability. Since the 1950s, the plateau has witnessed a distinct trend of warming and humidification, with a temperature rise exceeding the global average, an overall increase in precipitation, cryosphere degradation, and an imbalance in water resources. Analysis of long-term series data shows that precipitation and runoff in the source regions of the Yangtze River, Yellow River, Lancang River, and Yarlung Zangbo River exhibit characteristics of spatiotemporal heterogeneity and phased variation. From 1961 to 2024, precipitation in these river basins generally showed an increasing trend, but around 1998, precipitation trends diverged between the northern and southern slopes: rainfall in the Yellow River basin on the northern slope increased significantly, while rainfall in the basins of the Yangtze River, Lancang River, and Yarlung Zangbo River on the southern slope shifted from an increasing to a decreasing trend. In addition to the impact of precipitation, runoff in the source regions is also influenced by glacial meltwater. Taking the Zhimenda Station in the Yangtze River source region as an example, precipitation has decreased since 1998, but runoff has continued to increase. Runoff at the Tangnaihai and Lanzhou stations of the Yellow River has increased significantly with precipitation, reversing the decreasing trend observed before 1998. At present, the water resources of the Qinghai-Tibet Plateau face several challenges, including the depletion of solid water reserves, the short-term runoff increase driven by unsustainable glacial meltwater in the long run, altered seasonal runoff distribution, and intensified water security risks. To address these challenges, it is necessary to regulate human activities to mitigate the impacts of climate change, strengthen the rigid constraints on water resources, expand the utilization of unconventional water resources, and ensure the sustainable utilization of water resources.