Scale effect on runoff in alpine mountain catchments on China's Gongga Mountain

Abstract. Finding an effective method to upscale or downscale hydrological processes is the central concern in hydrological research. The aim of this paper is to investigate a powerful, regulated relationship between runoff and catchment area, and establish the runoff scale transfer model for Gongga Mountain in China. We chose a series of catchments in which the contributing areas ranged from 0.41 km² to 80.5 km² to monitor the hydrological processes and meteorological conditions since 1990. To identify the nature and causes of variation in the runoff response to the size of catchments, a two-stage scaling method was proposed to describe the processes of runoff scaling. The results indicated that runoff had a different statistical relationship in different seasons and the related parameters were also different. The scaling models indicated a higher simulation efficiency and precision between the observed runoff and the calculated runoff, and they also provided a practical way for upscaling or downscaling in an alpine mountain watershed. For alpine mountain catchments, the results showed that the vegetation type and cover might be important factors for the runoff response to the scale effective.