1. Institute of Soil and Water Conservation; Northwest A&F University; 26 Xinong Road Yangling 712100 Shaanxi Province China
2. Institute of Soil and Water Conservation; Chinese Academy of Sciences & Ministry of Water Resources; 26 Xinong Road Yangling 712100 Shaanxi Province China
3. State Key Laboratory of Hydroscience and Engineering; Tsinghua University; Beijing 100084 China
4. College of Resources and Environment; Northwest A & F University; Yangling 712100 Shaanxi Province China