This work uses the Soil and Water Assessment Tool (SWAT) ecohydrological model (https://swat.tamu.edu/) to evaluate the performance of dynamically downscaled regional climate simulations, under the support of the DOE FACETS and HyperFACETS projects. Previous work (https://doi.org/10.1016/j.scitotenv.2020.137562) indicated that a calibrated SWAT using PRISM weather data and the Hargraves potential evapotranspiration method were suitable for simulating streamflow in the Upper Mississippi River Basin (UMRB). Following the calibration and validation process, daily maximum and minimum temperature, and precipitation for a 15-year period (1991-2005) from ERA-Interim-driven WRF-ARW and RegCM4, at 12 km, 25 km and 50 km horizontal grid spacing, were input into SWAT. Simulated streamflow from these six SWAT runs were compared to observed streamflow data from multiple gauge sites in the UMRB. The results reveal that the simulated streamflow from the SWAT runs, using the dynamically downscaled regional climate model data, are greatly overestimated compared to observed streamflow. However, minimal bias occurs for evapotranspiration estimates compared to the SWAT run with PRISM. Further analysis indicates the wet-bias in the ERA-Interim-driven WRF and RegCM4 models are the most probable cause for the overestimation of simulated streamflow. Precipitation intensity and frequency are explored to quantify the source of the precipitation bias and its impact on simulated streamflow. Additionally, the water balance is examined to determine the effects of the precipitation wet-bias on water partitioning in the UMRB.