Modeling streamflow response under changing environment using a modified SWAT model with enhanced representation of CO2 effects

Authors: LI, BAOGUI - China Agricultural University; TAN, LILI - China Agricultural University; ZHANG, XUELIANG - China Agricultural University; QI, JUNYU - University Of Maryland; Marek, Gary; LI, YINGXUAN - China Agricultural University; DONG, XIAOJIE - China Agricultural University; ZHAO, WENJIE - China Agricultural University; CHEN, TING - China Agricultural University; FENG, PUYU - China Agricultural University; LIU, DE LI - China Agricultural University; SRINIVASAN, RAGHAVAN - Texas A&M University; CHEN, YONG - China Agricultural University

Submitted to: Journal of Hydrology: Regional Studies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/7/2023
Publication Date: 10/13/2023
Citation: Li, B., Tan, L., Zhang, X., Qi, J., Marek, G.W., Li, Y., Dong, X., Zhao, W., Chen, T., Feng, P., Liu, D., Srinivasan, R., Chen, Y. 2023. Modeling streamflow response under changing environment using a modified SWAT model with enhanced representation of CO2 effects. Journal of Hydrology: Regional Studies. 50. Article 101547. https://doi.org/10.1016/j.ejrh.2023.101547.
DOI: https://doi.org/10.1016/j.ejrh.2023.101547

Interpretive Summary: Climate change is expected to result in continued increases in air temperature and atmospheric CO2 concentrations. Although the long-term impacts of such increases are unknown, simulation modeling using global circulation models may provide insight into potential effects on water resources and streamflow. Researchers from USDA-ARS Bushland and university partners from the U.S. and China simulated the effects of climate change on precipitation and streamflow hydrology in the Haihe River Basin (HRB) in Northern China through the end of the of the 21st century. Simulations using an improved Soil and Water Assessment Tool (SWAT) model equipped with a dynamic CO2 algorithm suggested that both precipitation and streamflow increased overall while solar radiation varied considerably. Projected annual streamflow was greater in downstream plains than in upstream mountainous regions with several simulations suggesting increased flood risk by the end of the century. This study highlighted the efficacy of the improved SWAT model for identifying potential impacts of climate change on streamflow hydrology.

Technical Abstract: Changes in streamflow due to climate change are highly uncertain. In this study, impacts of climate change on streamflow variations in the Haihe River Basin (HRB) of the North China Plain were quantified using an improved SWAT model equipped with a dynamic CO2 input method. Climatic and streamflow changes were analyzed based on bias-corrected Coupled Model Intercomparison Project Phase 6 (CMIP6) climate projections of 22 General Circulation Models (GCMs) under four Shared Socioeconomic Pathways emission scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) during two 30-year periods of the middle (2041-2070) and end (2071-2100) of the 21st century relative to the historical period of 1971-2000. Long-term simulations of annual streamflow showed that the SWAT model using both the dynamic and constant CO2 input methods had similar patterns under the SSP2-4.5 and SSP3-7.0 scenarios, whereas substantial discrepancies appeared under the SSP1-2.6 and SSP5-8.5 scenarios in the HRB. The findings highlighted the importance of using the dynamic CO2 input method for streamflow simulations. Additionally, the prediction results of climate variables indicated that annual and monthly precipitation and air temperatures increased consistently, whereas the solar radiation distinctively varied with time and emission scenarios. According to the spatiotemporal analysis of streamflow using the improved SWAT model, the simulated results revealed that streamflow generally increased under four emission scenarios. In the HRB, annual streamflow in the downstream plains was higher than in the upstream mountains, and this was more evident under the severe emission scenario of SSP5-8.5. The strongest increment in streamflow was projected in the SSP3-7.0 and SSP5-8.5 scenarios, indicating that flood risk would possibly increase in the late 21st century.