Assessing the potential impacts of climate change on return periods of hydrological extremes in the Illinois River watershed of the Midwestern United States

Abstract:

As the Earth’s climate is predicted to change significantly in terms of warmer temperature and higher precipitation extremes during this century due to the increased combustion of fossil fuels, accurate estimations of the frequencies of future hydrological extremes are important to understanding the potential impacts of changes in climate on water resources management, particularly in accessing flood risk. The goal of this study is to use the Soil and Water Assessment Tool (SWAT), a distributed landscape-scale hydrological model, to predict current streamflow and the potential impacts of climate change on future stream flows in the Illinois River watershed in the Midwestern United States. Subsequently Gumbel distribution (Extreme Value Type Ⅰ) is fitted to the annual maxima simulated streamflow to derive a number of return periods of future hydrological extremes. The question in this study is: How do the return periods of future hydrological extremes change under future climate change scenarios and what factors cause the change? Daily simulated future streamflow from 2046-2065 and 2081-2100 are simulated using SWAT model based on nine separate downscaled global climate models (GCM) with three emissions scenarios. SWAT model predictions generally indicate that annual streamflow will likely decrease due to warmer temperatures. Based on the simulated daily streamflow, probability models for annual maxima flows frequency analysis are developed using Gumbel distribution and the values of hydrological extremes for different return periods including 50, 100, 200, 500, 1000 years are derived. The change of return periods of hydrological extremes and the implications will be discussed.