Research on streamflow and hydrological drought in lower Songhua River Basin under CMIP6 scenarios based on SWAT model

Abstract

[Objective] This study aims to investigate streamflow variations and hydrological drought characteristics in the lower Songhua River Basin under future climate scenarios, providing a scientific basis for regional water resource management and guidance for formulating comprehensive drought and flood disaster prevention and control strategies. [Methods] Based on hydrometeorological data from 1970—2014, a SWAT model was constructed and driven by 14 CMIP6 climate models. Five optimal climate models were selected through Taylor diagram analysis and combined with SSP1-2. 6, SSP2-4. 5, and SSP5-8. 5 scenarios to simulate streamflow variations from 2015 to 2100. [Results] The SWAT model demonstrated excellent performance at Tongjiang hydrological station, with R² and NSE values exceeding 0. 7 during both calibration and validation periods. The absolute values of PBIAS were below 10. 7%, confirming model reliability. Future climate predictions indicated increasing trends in precipitation, temperature, and evapotranspiration across the river basin. The magnitude of temperature and evapotranspiration increases followed the order of SSP5-8. 5 > SSP2-4. 5 > SSP1-2. 6, while precipitation increases ranked as SSP5-4. 5 > SSP1-2. 6 > SSP2-8. 5. Seasonally, SSP1-2. 6 and SSP5-8. 5 scenarios showed significant precipitation increases in autumn and winter, while SSP2-4. 5 scenario exhibited notable increases in summer and winter. Streamflow variations strongly depended on scenarios: SSP1-2. 6 showed significant increases, while variations under SSP2-4. 5 and SSP5-8. 5 were not significant. Standardized Streamflow Index(SSI) analysis showed significant increases under SSP1-2. 6, but declining trends under other scenarios. Drought characteristic analysis indicated that under SSP1-2. 6, all drought indices except average drought duration decreased, while under SSP2-4. 5 and SSP5-8. 5, all indices except drought frequency increased. Seasonally, SSP1-2. 6 increased spring-summer proportions with elevated winter drought frequency, while SSP2-4. 5 and SSP5-8. 5 increased autumn-winter proportions with corresponding frequency changes. [Conclusion] Future climate change will significantly impact hydrological characteristics in the lower Songhua River Basin. The SSP1-2. 6 scenario promotes streamflow increase and drought mitigation, while the SSP2-4. 5 and SSP5-8. 5 scenarios may exacerbate drought risks. The findings provide decision-making support for regional water resource management and disaster prevention, recommending differentiated adaptation strategies tailored to specific climate scenarios.

Keywords

lower Songhua River Basin / CMIP6 / hydrological drought / run theory / SWAT model / streamflow / shared socioeconomic pathways / influencing factors

Funding

National Natural Science Foundation of China(52109055)

Heilongjiang Postdoctoral Top-up Grant(LBH-Z24110)