Spatial variation of scale effects of specific sediment yield in Zhujiang

The scale effects of Area-Specific sediment yield (YS) are studied for Zhujiang basin and its four subbasins. Considering the entire Zhujiang basin, there is no apparent relation between Ys and contributing area (Ad) for stations when Ad is less than 100,000 km 2 , while there is an upper envelope outline of Ys. For the stations with Ad larger than 100,000 km 2 mainly located on the middle and lower reaches, there is a negative relation of Ys to Ad. Considering the four sub-basins of Zhujiang basin, three kinds of relations between YS and Ad are established: (1) Ys increases with Ad for the sub-basin of the upper reach; (2) Ys increases with Ad then declines for the two sub-basins of the middle reaches; (3) Ys decreases with Ad for the sub-basin of the lower reaches. The YseAd relation is further investigated using the spatial variation of hill slopes, the Land Use and Land Cover (LULC), and the bed slopes. Finally, to remove the effect of Ad and to make Ys comparable across scales, the scaled Ys calculation equations are given for both linear and non-linear relations between Ys and Ad first. And then the Ys are scaled to the standard units of 1000 km 2 and 10,000 km 2 . Using Kriging method, the Ys maps are created under GIS platform where high Ys centers are outlined, and the spatial patterns of Ys are compared for the two standard unit Ys maps.