Abstract:

Since 1990s',research of ecoenvironmental water requirement for river has become an important part for ecohydrology research.According to ecohydrology theory,the conception of ecoenvironmental water requirements and the meaning were clarified.Based on the Pihe River Water Switch Project research,ecoenvironmental water requirements were expressed by flux which contained time information,not just water quantity.To coordinate with the water resource allocation,the article evaluated ecoenvironmental water requirements for three typical years,they were 〖WTBX〗P〖WTBZ〗=50%（1968），〖WTBX〗P〖WTBZ〗=75%（1986） and 〖WTBX〗P〖WTBZ〗=90%（1987）.Based on natural characters of Pihe River,the minimum and optimum water requirements of aquatic habitat for the river maintenance were counted by the means of Montana Theory.The Pihe River evaporation water requirements were counted too,which were related with the width of water surface,the length between two sections and the evaporation depth of the river.The pollutant dilute water requirements were counted on the combination of water quality goal and river function division.The minimum and optimum ecoenvironmental water requirements of river were ultimately ascertained as 20.64 m3/s and 25.84 m3/s respectively.According to the case study of Pihe River,it can be concluded that ecoenvironmental water requirements of river is not a numerical number,but a scope,which is practical to ensure the basic flow to downstream of water power station dam,and helpful to protect the ecoenvironment of the river,especially for downstream watershed.

Key words: ecoenvironmental water requirement, water resource allocation, target of water quality, water requirement for pollutant dilution