Response of runoff and suspended load to climate change and reservoir construction in the Lancang River

Abstract

With the operation of six cascade reservoirs, the flow regime and sediment discharge of the Lancang River have changed greatly. The changes of runoff and suspended load have attracted extensive attention. The hydrological data of Gajiu and Yunjinghong stations in Lancang River from 1964 to 2019 were analyzed by using wavelet analysis, double mass curve and abrupt change analysis. The temporal trends in runoff and suspended load were evaluated. Results revealed that the reduction of suspended load was much more profound than the change of runoff. There was a slight downward trend in annual runoff due to climate change. After the completion of Xiaowan and Nuozhadu reservoirs, the proportion of runoff in flood season decreased by 22.64 and 30.75%, respectively. Wavelet analysis was used to reveal the characteristics of runoff evolution. With the operation of reservoirs, suspended load showed abrupt changes in 1993 and 2008. The amount of suspended load during 2009–2019 decreased by 95.47–98.78% compared with that before the reservoir construction. This paper presents the latest quantitative study on the temporal variation of runoff and suspended load since the completion of Xiaowan and Nuozhadu reservoirs, which is of great importance for guiding the operation of reservoirs and maximizing the value of the whole Lancang-Mekong River basin. HIGHLIGHTS Variations of runoff and suspended load during 1964–2019 in Lancang River were first quantified in detail after Xiaowan and Nuozhadu reservoirs were completed.; The total amount of runoff was dominated by climate change, while reservoir construction mainly influenced the annual process of runoff.; Suspended load exhibited abrupt changes in 1993 and 2008 and the reduction reached 95–99% after the reservoir construction.;

Keywords

• runoff
• climate change
• lancang river
• reservoirs
• suspended load