Abstract. The evolution routes and development stages in hydrological sciences are summarised from the following three dimensions: research object, discipline and methodology, by means of the descriptive-explanatory-humanistic ideology. Modern technical breakthroughs and socioeconomic developments have promoted hydrology from geographical hydrology, engineering or applied hydrology to water resources hydrology in terms of the focus of research objectives or problems. It has been observed from the point of view of methodology that hydrological sciences go through deterministic hydrology, stochastic hydrology, isotope hydrology, digital hydrology, etc. Hydrological sciences in the context of discipline dimensions can be divided into three main categories: physical hydrology, chemical/environmental hydrology, biological hydrology including eco-hydrology and socio-hydrology, although there are overlaps between these due to the complex and intertwined water-related challenges facing the hydrological community and other geosciences. Humans have played a significant role in changing land uses throughout the world and therefore, socio-hydrology is an increasingly significant branch of the hydrological sciences. It can be seen from analyses that biological hydrology is a new approach to cope with global change issues, and a new frontier direction in the field of hydrological sciences. It can also be seen from dialectical analysis of the different stages in the evolution of hydrology, that new frontiers or directions requiring investigation, scientific recognition and technical innovation will continue to be generated in the field of hydrology. The 3-dimensional diagram of evolution routes of hydrological sciences may provide some ideas for Panta Rhei, the new IAHS Science Initiative 2013–2022 for hydrological research under changing human and environmental systems in the real world.