The Great Lakes Basin (GLB) in North America is home to over 30 million inhabitants and contributes more than 6 trillion dollars to the US GDP annually. Of which, ~20% is generated from agriculture, making it the 2nd largest primary sector in the region’s economy. Thus, understanding the long-term impacts of climate change on the GLB hydrology is crucial for ensuring the well-being of its people, economy, and environment. In this study, I investigate the impacts of climate change on the hydrodynamics of the GLB by analyzing (1) historical data and (2) projected future conditions. The CaMa-Flood model, a high-resolution (~5km with flood attributes downscaled to ~90m) hydrodynamics model, is forced by combinations of different hydrological and global climate models from various sources to simulate future conditions under 3 socioeconomic development pathways, combinations of Representative Concentration Pathways and Shared Socioeconomic Pathways (RCP 2.6-SSP1, RCP 4.5-SSP3 and RCP 8.5-SSP5) over an 85-year period (2015-2100). Historically observed data from 254 USGS stream gauge stations showed that 87.8\% showed an increasing trend in water volume over the past 25 years, which has been linked to changes in precipitation, snow-melt timing, and increased magnitude and frequency of hydrological extremes including floods and droughts. Simulation results suggest that this trend is likely to continue into the future. First, substantial changes are expected in the seasonal hydrologic regime throughout the GLB, especially a major shift in the timing of peak flows from spring to winter, by up to a month in some areas by the end of the 21st century. Furthermore, results also suggest an overall increase in water balance, indicated by an increase in mean surface water storage by up to 20% in some areas. This is also reflected by an increase in lake water levels. Moreover, the frequency of extreme floods increases by 400-2000\% under all climate change scenarios by the late century, especially SSP3 and SSP5. This study provides a comprehensive analysis on the impacts of climate change on the hydrology of the GLB, allowing for the anticipation and design prevention of future devastating hydrological events.
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