Spring floods in the Red River basin generated from melting snow have increasingly affected the Fargo-Moorhead metropolitan region of North Dakota and Minnesota within recent decades, causing serious economic damage and disturbance to the local community. Various local and federal government agencies have come together to formulate a flood management project mainly utilizing water diversion to protect the Fargo-Moorhead urban area from future floods. Major structural measures that alter the surface water flow regime would take place under the current project proposal. This study applied the Hydrologic and Water Quality System to set up the study watershed, covering the upper portion of the Red River basin with its outlet located in Fargo. The Soil and Water Assessment Tool Calibration and Uncertainty Procedures were used to perform sensitivity analysis, model calibration, and model validation on a chosen set of hydrologic input parameters. Results from one of the general circulation models, the Geophysical Fluid Dynamics Laboratoryโs global coupled carbon-climate earth system model with vertical coordinates based on density, were coupled with the hydrologic model to set up predictive simulations to evaluate climate change impacts on the study watershed. A flood diversion channel was added into the predictive simulations in the form of point-source water extraction. The time durations for the predictive simulations were divided into two decade-long sections, 2026 to 2035 and 2036 to 2045, which represent the short- to medium-terms following project construction completion. Results of the predictive simulations indicate a significant increase in streamflow for the entire
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simulation time span under both RCP4.5 and RCP8.5 climate change scenarios. Meanwhile, the implementation of a diversion channel near the Fargo-Moorhead urban area would have a strong impact on the flow regime of the Red River at Fargo, where a streamflow pattern with lower average discharge and lower flow variability is predicted for the flood-diversion-included simulations. The inclusion of the flood diversion channel in the model also significantly reduces the occurrence of large-magnitude streamflow events
