CLIMATE CHANGE MITIGATION EFFECTS OF SMALL SURFACE WATER BODIES IN MISSISSIPPI RIVER BASIN, USA

Surface water storage in small yet abundant depression landscapes, such as ponds and wetlands, influences downstream water flows. However, process-based model simulations of floods and droughts in response to climate change effects only consist of larger water bodies, such as lakes and reservoirs. This provides potential inaccuracy of traditional hydrological models and their relationship to climate change variations across major river basins. To further understand and mitigate this limitation, a surface depression-integrated continental-scale hydrological model of the 3.3 million km² Mississippi River Basin (MRB) in the United States was used for interpretation. Use of the Soil and Water Assessment Tool (SWAT) allowed for hydrological simulation of the six major watersheds of the MRB. The six watersheds were then calibrated through SWATCUP with use of USGS discharge data. The assessment of surface depressions was provided through a novel topography-based algorithm to estimate areas and volumes across the MRB and aggregate their effects to each sub-basin. Lastly, TerraClimate precipitation data was used as a proxy for future climate conditions under 2- and 4- degree Celsius warming scenarios. In comparison to the “no depression” model, the depression-integrated model displayed an alteration of spatial patterns and magnitudes of water yields across the MRB. This suggests that the process-based model simulations were of incomplete representation when ignoring small depression landscapes in the traditional hydrological estimates regarding future climate change impacts.