Basic problems and frontier of hydrology

In this article, we reviewed the history of the development of hydrological science in People's Republic of China for the past 70 years. We also discussed the basic scientific questions of hydrology and its current frontier, which include the hydrosphere and its interface with other spheres of the earth, the hydrological cycle system and the disturbance of human activities to it, the hydro-observation and the methodology of hydrology research, the application of hydrological knowledge, etc. Based on these studies, we suggest to divide the hydrological science into five sub-disciplines:General hydrology, Hydro-meteorology, Land-hydrology, Eco-hydrology, and Applied hydrology.