Precondition analysis on annual flood resources exploitation of the Yongding River
zhang shao-wen~1 wu wen-yong~1 hao zhong-yong~1 yang sheng-li~1 yin yue~2 (1.beijing hydraulic research institute; beijing; 100044; china; 2.flood control and drought fighting headquarters office of beijing municipal goverment; 100038; beijing; china)