Xiaolangdi Dam: A valve for streamflow extremes on the lower Yellow River

Water problems have long been among the most urgent issues affecting China's lower Yellow River. In recent decades, the regime of the streamflow flowing into the lower Yellow River has been significantly altered by large reservoirs and dams. In this work, we investigate the valve function of Xiaolangdi Dam on the water discharge for multiple scales. Xiaolangdi Dam exhibits little impact on the total streamflow in the long run, although it dramatically changes the seasonal distribution. The ratio of average daily discharge during non-flood seasons to average daily discharge during flood seasons at Xiaolangdi station increased progressively from 39.8% during 1971-1989 to 93.2% during 1997-2016. Based on a linear relationship determined from historical data, the theoretical daily discharge at Huayuankou station in the absence of Xiaolangdi Dam was reconstructed. Through comparative analysis of the observed and reconstructed daily discharge series, we estimate that 78% of the potential flood events that could have happened during 1997-2007 were mitigated due to the construction and operation of Xiaolangdi Dam. Meanwhile, the peak discharge at Huayuankou station was also reduced from > 6000 m(3)/s to < 4500 m(3)/s. The redistribution of seasonal discharge by Xiaolangdi Dam not only is beneficial for meeting water demand but also effectively extirpates the river drying-up phenomenon.

Automated summary

This study investigated the impact of Xiaolangdi Dam on water discharge at multiple scales. The results showed that the dam had little effect on the total streamflow in the long run, but significantly changed the seasonal distribution. Through data reconstruction, it was estimated that the dam's construction and operation mitigated around 78% of potential flood events. The construction of Xiaolangdi Dam is of great importance for meeting water demand and eliminating the drying-up phenomenon in the river.