AUTHORS: ANDRE R. ERLER, STEVEN K. FREY, OMAR KHADER, MARC D’ORGEVILLE, YOUNG‐JIN PARK, HYOUN‐TAE HWANG, DAVID LAPEN, W. RICHARD PELTIER, EDWARD A. SUDICKY
This study aims to assess the impact of climate change on water resources in a large watershed within the Laurentian Great Lakes region, using the fully‐integrated surface‐subsurface model HydroGeoSphere. The hydrologic model is forced with an ensemble of high‐resolution climate projections from the Weather Research and Forecasting model (WRF). The latter has been extended with an interactive lake model (FLake) to capture the effect of the Great Lakes on the regional climate. The WRF ensemble encompasses two different moist physics configurations at resolutions of 90km, 30km, and 10km, as well as four different initial and boundary conditions, so as to control for natural climate variability. The integrated hydrologic model is run with a representative seasonal cycle, which effectively controls natural climate variability, while remaining computationally tractable with a large integrated model. However, the range of natural variability is also investigated, as are the impact of climate model resolution and bias correction. The two WRF configurations show opposite climate change responses in summer precipitation, but similar responses otherwise. The hydrologic simulations generally follow the climate forcing; however, due to the memory of the subsurface, the differences in summer propagate throughout the entire seasonal cycle. This results in a set of dry scenarios with reduced streamflow and water availability year‐round; and a set of wet scenarios with increased streamflow for all times excluding the spring peak, which does not increase. Most of the analysis focusses on streamflow, but changes in the seasonal cycle of baseflow and groundwater recharge are also analyzed.