Climate Change Impacts on Flow, Sediment and Nutrient Export in a Great Lakes Watershed Using SWAT

This study aims at understanding the impacts of projected climate change on the hydrological processes within the Maumee River watershed (16395 km²) lying in the Lake Erie Basin using soil and water assessment tool (SWAT). The model was calibrated and validated for a baseline time-period of 1995-2005. Downscaled ensemble projected temperature and precipitation data from three general circulation models (GCMs) was then used to assess future flow, sediment, and nutrient loading in the watershed for mid-century (2045-2055) and late-century (2089-2099) time periods. Compared to the baseline, a 2.9°C rise in the annual average temperature along with a 3.2% fall in the annual precipitation in the mid-century time-period is projected to reduce annual flow volumes, and suspended solids (SS), total phosphorus (TP), nitrate (NO₃) loads by 8.5, 10.4, 8.5, and 9.9%, respectively. Similarly, for the late-century a 4.3°C rise in the annual average temperature along with a 5.6% rise in the annual precipitation is projected to increase annual flow volumes, and SS, TP, NO₃ loads by 9.7, 19.6, 3.5, and 6.8%, respectively. Temporal shifts in climatic conditions were also projected for both the future time-periods with higher temperatures throughout the year along with wetter winters and drier summers. Implications of these changes would include the need for an increased focus on pollutant loadings for total maximum daily load guidelines and possible lengthening of crop growing cycles.