Background Soil erosion destroys soil and water resources, exacerbates natural disasters such as droughts and floods, and threatens human survival and development. Qujiang River Basin is severely affected by soil erosion, and runoff erosion power can reflect dynamic characteristics of water erosion better than rainfall erosion force. Therefore, it's important to use runoff erosion power theory to study erosion in Qujiang River Basin to reveal mechanism of water-sand response.

Methods This paper took Qujiang River Basin as a research object, calculating seasonal as well as annual runoff erosion power based on runoff, which was simulated by SWAT model in terms of utilizing meteorological forcing data such as precipitation, temperature, wind etc. In addition, features of spatial-temporal pattern and effects of spatial scale were analyzed. Cluster and correlation method were adopted for investigation into relationships between runoff erosion power with meteorological, topographic and soil conditions.

Results 1) The constructed SWAT model had high accuracy in runoff simulation and good applicability in Qujiang River Basin. R² and NS coefficients were 0.69 and above, while PBIAS coefficient was below 16.72 % in both parameter rate setting period and validation period. 2) In aspect of time, annual runoff erosion power outweighed that in season. However, erosion during season Ⅲ was more serious than that in other season, which requires more attention on soil erosion prevention and control. Besides, runoff erosion power for whole year and for season Ⅲ demonstrated a decreasing trend from north to south, west to east and up to down inspace. 3) The thresholds of drainage control area for whole year in Qujiang river and Datong river were 8 549.4 and 8 504.4 km² respectively, while those for season Ⅲ were 4 834.9 and 6 223.5 km² respectively, indicating runoff erosion power decreased smoothly with increasing area when the area was larger than spatial thresholds, then gradually tended to a stable value. 4) Meteorological, topographic and watershed morphological characters were main factors influenced runoff erosion power in Qujiang River Basin. Erosion in upstream area of basin presented greater performance than downstream, due to the steep topography, uneven precipitation distribution and morphological ease of runoff generation and flow concentration processes in upper reaches.

Conclusions This paper illustrated feasibility of SWAT model and its simulated outcome in Qujiang River Basin. The spatial-temporal runoff erosion power characteristics together with impacts are closely related to meteorological constituents, terrain and basin shape. Therefore, the results contribute to effective identification of key sand producing areas in watershed, and also provide supports for soil erosion prevention, ecology restoration and environmental carrying capacity enhancement.