Water is the most ？important element in ecosystems. With？ increased human activities, the？ traditional management of water？ resources is difficult to resolve the ？problems of ？fresh water shortage, water quality deterioration, decline in bio-diversify and other ecological roblems. Integrating？？？ the？ relationship？ between？ hydrological cycle and？ ecosystems,？ associating with the s tudy of the physical？ and？ chemical？ mehanisms of interaction between hydrological ？processes and？ ecological？ processes,？ searching for ecology？ beneficial and？ sustainable use of water resources management are important issues needed to resolve. Ecohydrology is the hot spot of many？ international？ research projects carried out in the？ world, such as the International Geosphere-Biosphere Program-aspects of the biosphere (IGBP-BAHC), the UNESCO International Hydrological Program (UNESCO IHP) and so on. All these？ projects？ regard？ ecohydrology ？as an？ important research topic.Ecohydrology research provides a new opening field for sustainable use of water resources.

There are many factors which i nfluence the processes of？ ecohydrological, and all of them have obvious temporal and spatial variability. With the？ development of RS, GIS and？ computer ？technology, computer simulation becomes an important method to study the processes of ecohydrology. Using the GIS platform, RS technology for spatial information access, establishment of regional？ scale？ distributed ecohydrological model becomes the new direction of hydrology and water resources research.

Under guidance of the Academician Liu Changming and Academician Li Xiaowen, the research group of Prof. Yang？ Shengtian, Prof. Hao？ Fanghua and Prof. Cheng？ Hongguang focuses on the？ eco-hydrological processes mechanism ？and their？ simulation. The group’s research bases on the principle of c onservation of ？matter and energy, studies the mechanism？ of ecohydrological processes, integrates RS, GIS and computer technology, combines with the ？long-term？ field-based？ observation？ and manual？ simulation experiment, couples with the ecohydrological processes model with the physical and chemical mechanism, independently developes a regional scale distributed ecohydrological modeling system EcoHAT.

EcoHAT model bases on the mechanism of ecohydrological processes. Its core components include energy and water cycles module, transportation and transformation of material module, basin ？ecological？ ？simulation module, etc. It’s a powerful tool for ecosystem and environment-related researchers to conduct the study of land surface evapotranspiration, soil water movement, vegetation NPP,ecological water requirement, vegetation？ nutrient cycling, soil nutrient c ycling and other eco-hydrological processes. The system provides many analysis modules, such as simulation of the vegetation productivity response under stress condition, simulation of？ non-point source pollution control effects by the riparian, calculation the amount of soil erosion, estimation the load of？ non-point source pollution. To achieve the dynamic evaluation of ecological？ benefits and the virtual design of the optimal？ environment, it also provides？ eco-efficiency evaluation, eco-design and other？ functional modules. EcoHAT provides effective scientific analysis and？ management tools？ for？ broad fields, such as Water Resources, Environment,？ Agriculture, Forestry, Land？ management and other？ relevant？ research institutions and enterprises.