Abstract: Based on the fractal theory and the long-term daily discharge records, this paper analyzed the fractal characteristics of daily discharge in mid-scale watershed (Wushui watershed) and small-scale watersheds (Zhenfu and Shuangxi watersheds). Under the same time scales and different threshold values of daily runoff, the fractal characteristics of daily discharge in the watersheds of different spatial scales and of same spatial scales were evident, and existed self-similarity. With the increase of the threshold values of daily runoff, the fractal dimensions of the daily discharge of different space-scale watersheds decreased gradually. The set of fractal dimensions of the daily discharge in different space-scale watersheds tended to be saturated when the time scale was 120-150 days, and the critical threshold values of daily runoff might appear when the time scale exceeded this number of days.  

Key words: daily discharge, spatial scale, fractal theory, fractal dimension, watershed, coastal saline soils, hyperspectral parameters, soil moisture content, hyperspectral remote sensing.