Status: this discussion paper is a preprint. It has been under review for the journal Hydrology and Earth System Sciences (HESS). The manuscript was not accepted for further review after discussion.
The effect of Three Gorges Dam and rainfall on summer flow risk over Yangtze River Basin
Zhenkuan Su,Zhenchun Hao,Michelle Ho,Upmanu Lall,Xun Sun,Xi Chen,and Longzeng Yan
Abstract. As the largest water conservancy project, Three Gorges Dam starts its impoundment in 2003 and henceforth the efficient operation of a multi-purpose dam has aroused a great concern on the effectiveness on flood control and water management over Yangtze River Basin. In this paper, we consider the relationship between rainfall from 136 weather stations and streamflow from 5 hydrological stations including Cuntan, Yichang, Luoshan, Hankou and Datong. Meanwhile, the spatial average rainfall over 21 subbasins was computed. The analysis of the correlation demonstrated that the correlation of spatial average rainfall and streamflow for each station is consistent with that between rainfall by stations and streamflow. Then, two options were selected to develop the linear models, including option a) using rainfall by stations to forecast streamflow and option b) using spatial average rainfall to forecast streamflow. The canonical correlation analysis enabled a large degree of spatially coherent information of rainfall by linear transforms to maximize the correlation of rainfall and streamflow for developing linear models. The model resulting from option b) best fits the observations. Coefficient of determination for each model and statistics such as reduction of error, coefficient of efficiency under cross validation serve as a test of good performance of the model. An analysis of streamflow characteristics across the stations illustrated that the streamflow of Cuntan and Yichang have different modes of variability from that of the rest stations below the dam. The comparison of risk type changes between observations and predictions during the post-dam period showed the dam effectively relieved the risk of upstream while not always played a positive role in risk mitigation of downstream. The spatial and temporal patterns of rainfall anomalies over the whole basin helps to explain how the dam impact the streamflow. Some applications as to possible operational strategies are discussed.
How to cite. Su, Z., Hao, Z., Ho, M., Lall, U., Sun, X., Chen, X., and Yan, L.: The effect of Three Gorges Dam and rainfall on summer flow risk over Yangtze River Basin, Hydrol. Earth Syst. Sci. Discuss. [preprint], https://doi.org/10.5194/hess-2017-159, 2017.
Received: 20 Mar 2017 – Discussion started: 27 Mar 2017
We examined the potential to use the basin-scale rainfall to directly model the streamflow and evaluate the effect of dam operations on summer flow risk over Yangtze River Basin. The result show that floods and droughts experienced in the post dam period were amplified, driven, or alleviated. The approach demonstrated here enabled one to develop and test both the rainfall induced variations and changes due to human activities on a river.
We examined the potential to use the basin-scale rainfall to directly model the streamflow and...