Soil water dynamics has been a new research field in hydrology and water resources since the 1980s. Research progresses in soil water dynamics achieved in the past decades greatly promoted the advances of sciences and technologies in the fields of irrigation and drainage,hydrology and water resources in China. Based on the soil water dynamics,the mechanism and laws of the water-heat-solute transfer in the unsaturated zone were revealed and understood. The theory of water and heat transfer in the Soil Plant Atmosphere Continuum (SPAC) was developed in 1990s (so called SPAC theory). The field scale crop model was developed rapidly based on SPAC theory,and the crop models became the major tool for study the impacts of climate change on agricultural water management and food production in the 21st century. At the same time,a number of scientific and practical issues were raised,such as the water transfer crossing the field scale to regional scale,multi-scale efficiency of the agricultural water utilization,ecological and environmental impacts of water resources development and utilization and so on. To solve these urgent issues and challenges,a new cross discipline of hydrology and ecology has been proposed,it is ecohydrology. Ecohydrology is based on the dynamics of water-energy-substance cycle,focuses on the basic scientific question of the climate-vegetation-hydrology interaction,and aims to serve the regional water resources management and eco-environment assessment and management.