Acknowledgements

This study was partly done while the first author was at the Institute of Hydrology and Water Resources of Tsinghua University in cooperation with the Akesu River Administrative Agency, and was funded by the World Bank. The authors would like to express their acknowledgement to all the scientists involved in the fieldwork, especially to Prof. Zhidong, Lei and Prof. Yang, Shixiu of the Tsinghua University. This work was also supported, in part, by the Japanese Ministry of Education, Science, Sports and Culture (Monbusho). The authors thank two anonymous reviewers for their helpful and constructive comments regarding an earlier version of this paper. Finally, we wish to thank Magnus Bengtsson for his careful revision of the language of this manuscript.