IMPACTS OF CLIMATE CHANGE ON HYDROLOGICAL COMPONENTS IN THE UPPER MISSISSIPPI RIVER BASIN

Quantifying the hydrological response to increased atmospheric CO₂ concentration and climate change is critical for evaluating regional water resource security. In this study, the potential impacts of variation in atmospheric CO₂, temperature, and precipitation based on Intergovernmental Panel on Climate Change projections are simulated using the Soil and Water Assessment Tool (SWAT). The readily available spatial layers of DEM, land use, and soil data are used to set up the model over the Upper Mississippi River Basin (UMRB). The model is first calibrated using an eight-year (2001–2008) record of daily streamflow and sediment at the outlet (Grafton, IL) of the watershed, which controls a drainage area of 443,667 km², and then validated with data collected during another eight years (1993–2000). The preliminary results show that climate change has significant effects on hydrological elements (e.g., water yield and evapotranspiration) in the study area. For example, a doubling of atmospheric CO₂ to 660 ppm results in around a 30% increase in the 50-year average annual streamflow and about a 20% decrease in potential evapotranspiration, while a change of precipitation by ±10% generally changes water yield around ±20% correspondingly. Moreover, the effects of climate change on groundwater recharge and sediment yield are also examined under the different future climate scenarios.