Wet-dry runoff correlation in Western Route of South-to-North Water Diversion Project, China

The Western Route of the South-to-North Water Diversion Project is an important trans-basin diversion project to transfer water from the upstream Yangtze River and its tributaries (water-exporting area), to the upstream of the Yellow River (water-importing area). The long-term hydrological data from 14 stream gauging stations in the Western Route area and techniques including the pre-whitening approach, non-parametric test, Bayes law, variance analysis extrapolation, and Wavelet Analysis are applied to identify the streamflow characteristics and trends, streamflow time series cross-correlations, wetness-dryness encountering probability, and periodicities that occurred over the last 50 years. The results show that the water-exporting area, water-importing area, and the stretch downstream of the water-exporting have synchronization in high-low flow relationship, whereas they display non-synchronization in long-term evolution. This corresponds to the complicated and variable climate of the plateau region. There is no obvious increasing or decreasing trend in runoff at any gauging station. The best hydrological compensation probability for rivers where water is diverted is about 25% to 10%, and those rivers influenced significantly by diversion are the Jinsha and Yalong rivers. Proper planning and design of compensation reservoirs for the water-exporting area and stretch downstream of the water-exporting area can increase the hydrological compensation possibility from water-exporting area to the water-importing area, and reduce the impact on the stretch of river downstream of the water-exporting area.