Characteristics of extreme hydrological evolution in Nenjiang River Basin under future climate change scenarios

Abstract

[Objective] Global climate change causes frequent occurrence of extreme hydrology, threatening regional water security and ecological security. The Nenjiang River Basin is located in the middle and high latitudes and is highly sensitive to global changes. However, how hydrological extremes will evolve under future climate change remains unclear. [Methods] Selecting the Dalain Hydrological Station, a control hydrological station in the Nenjiang River Basin, changes in hydrological extremes were investigated under future climate change. The meteorological data under different SSP scenarios(SSP126, SSP245, and SSP585) of CMIP6 were used as driving climatic factors. The calibrated and validated HYDROTEL model was employed to simulate the daily runoff volume from 2025 to 2100 under future climate change. Peak flow indicators(maximum daily flow, maximum 5-day flow, and flood days) and low-flow indicators(low-flow days and consecutive dry days) were extracted to analyze the extreme hydrological evolution characteristics of the Nenjiang River Basin under future climate change. [Results] The result showed as follows:(1) Under future climate change, the variation trend of extreme hydrological risk in Nenjiang River Basin under different SSP scenarios will be divergent. There is no significant change trend in the peak discharge index under the three scenarios. In the SSP1-2.6 scenario, the low water flow index will witness a significant upward trend, while in the SSP3-7.0 scenario, the low water flow index will experience a significant downward trend. Under the SSP5-8.5 scenario, the number of consecutive drought days will witness a significant decreasing trend.(2) The change trend and fluctuation characteristics of peak flood discharge index and low water discharge index are different in different periods. In the three scenarios, the mean values of different indicators in the near term(2025—2050), the medium term(2051—2070) and the long term(2071—2090) show certain differences compared with the historical period. Particular in the scenario of SSP5-8.5, the mean values of the long-term maximum daily flow and the maximum 5 d flow will be 44.3% and 38.2% higher than during historical period respectively. [Conclusion] Under the future climate change, the intensity and frequency of floods will show a significant upward trend, while the intensity and frequency of droughts will show a certain downward trend in the Nenjiang River Basin. It can provide important references for the mitigation of agricultural drought and flood risks, water security guarantee, and comprehensive water resources management in the Nenjiang River Basin.

Keywords

Nenjiang River Basin / historical period / future climate / extreme hydrological index / trend / spatiotemporal changes / extreme precipitation / flood