Abstract: Ecological water right is an important component of initial water rights, while ecological water requirement (EWR) is the manifestation of ecological water right. To calculate the instream EWR can provide basis for the allocation of water right and the protection of ecological environment. Based on the investigation of Taizi River, and by the monthly-guaranteed-frequency method and fish habitat method, this paper calculated the instream EWR of Taizi River, and the calculated results were verified with Tennant method. It was shown that the calculated results by the monthly-guaranteed-frequency method and fish habitat method were reasonable. According to the tradeoff between water resources and actual water use status, the minimum, medium, and ideal grades of annual EWR in different reaches were determined. Comparisons between the calculated results of different grade EWR and the measured streamflow in different reaches indicated that the measured streamflow at different hydrological stations basically satisfied the minimum grade of EWR. As for the medium and ideal grade EWR, various measures should be taken to reserve the water in the instream for the guarantee of ecological water right.

Key words: Forest evapotranspiration, Model, Energy balance, Aerodynamics