Hydrologic Modeling of Climate Scenarios for Two Illinois Watersheds

Watershed modeling applications for the Fox and Iroquois River watersheds in Illinois were used to evaluate the response in simulated streamflow to various climate scenarios. The climate scenarios applied to both watersheds are based on simulations from two global climate models, the Japan and Hadley models, which respectively represent comparatively “dry” and “wet” scenarios of future climatic conditions. The “Dry” climate scenarios result in a considerable reduction in the simulated flows for both modeling applications, although the specific amount of reduction varies considerably between the two applications. The “Wet” climate scenarios cause relatively small amounts of change in simulated streamflow amounts. For the Fox River watershed, changes in most flow parameters for the “Wet” scenario are less than 10 percent; whereas for the Iroquois River watershed, the changes are generally less than 15 percent. In particular, results indicate that increases in precipitation values may not necessarily translate into increased flooding conditions if also accompanied by warmer temperatures. The two watershed applications use different hydrologic simulation models, which is useful since the “true” hydrologic response to variations in climate is unknown and using different models can present a range of credible simulated hydrologic responses. However, more work is needed to identify and separate the varying responses related to different model algorithms versus the varying responses related to the physical characteristics of the individual watersheds being modeled.