Red-Crowned crane is an endangered species whose population in the world is 1000-1200, the 2/3 of which live in China. Xianghai wetland in Jilin Province is one of their breeding places. In this study, hydrological condition of the wetland is investigated in relation to the cranes' nesting: Twelve scenes of Landsat-TM data were analyzed to estimate the water area as well as the area of “reed colonies in the water” that is the most favorable places for the cranes' nesting. The results of analysis agreed well to the facts obtained from field observations in the past. The analysis also showed that the reed colony becomes richer as the total water area gets larger. Then, the variation of water area in Xianghai for twenty years was obtained from 145 scenes of Quick-look images by eyes. Using the data, empirical equations were constructed for predicting the variation of water area from basic hydrological factors such as rainfall and river flow rate. A critical river flow rate for the conservation of the cranes' habitat in Xianghai wetland was discussed, being based on the empirical relations as well as the facts observed at the site.
