Synthesis of climate-water-food nexus in Illinois – data analysis and modeling

The climate is expected to change in the near future due to the global warming caused by anthropogenic release of greenhouse gases. Global warming is going to affect the atmospheric process (climate), biosphere process (hydrology) and the biological process (crop yield). Thus, the global warming will impact the nexus between climate-water-food. In this study, a methodology was developed to explore the threat posed by global warming on the climate-water-food nexus in the US Midwest dominated by rain-fed agricultural systems by leveraging data analysis and simulation modeling approaches. In accordance with the first step of the nexus, the historical temperature and precipitation time-series data were analyzed. The main objective of this analysis was to identify if these two climatic parameters have undergone any long-term change in the last half century when the impacts of global warming started to manifest themselves. Once the changes in temperature and precipitation were analyzed, the hydrological time-series data was also analyzed to determine if the climate change, and more specifically, precipitation change had driven any change in the hydrological regime. Under the condition that a shift in the hydrological regime is established, the next objective of this study was to determine the driver of such shift. Hydrological patterns are known to change by changes in atmospheric conditions driving the change in precipitation and temperature. The land phase of the hydrological process is also affected by the changes in the land use patterns such as deforestation, urbanization, and intensification in agricultural practices. In the rain-fed watersheds of the central Illinois, an upgrade in tile drainage systems in the 1970s, followed by the intensification of the cropping density in the recent decades have been identified to have driven a change in runoff processes from the land surface and tile drains. The next step in the implementation of the methodology involved the use of climate projections to analyze the impacts of climate change in the early and late century. But before the climate projection data can be used, it had to be tested for its ability to replicate the historical climate observations. If any bias in the projections are detected during such comparison, the data has to be processed to rectify such bias. In this study, the historical projections of temperature and precipitation were bias-corrected using quantile-mapping techniques. The bias-corrected data was then compared with the historical observations to identify if the bias-correction was able to improve the predictive skills of the climate projections. After that, the bias-corrected future climate data was explored to acquire an understanding of the long term outlook of the climate in the state of Illinois. Finally, a hydrological model for Embarras watershed – an agriculturally dominant rain-fed watershed of central Illinois – was developed. The model was calibrated for hydrology, nutrient transport and crop yield. The model was then forced with the bias-corrected climate projections data and the impacts of climate change on hydrology, nutrient transport and crop yield was analyzed. No significant change in average daily, daily maximum and daily minimum temperature was detected for Illinois. From the analysis of the extreme temperature events it was observed that number of extremely hot days is decreasing and the number of warm nights is increasing. It was also found out that within the cropping season, the number of days with temperature within the growing degree days temperature for corn are increasing. From the analysis of precipitation data, it was found out that 40% of the observed stations had evidence of significant increase in precipitation. With further analysis, it was established that the increase in precipitation was driven by increase in both precipitation days and extreme precipitation events. From the study of the hydrological data from 6 watersheds of Illinois, significant shift in runoff was detected for the agricultural watersheds, whereas, no such shift could be established for forested watersheds. With precipitation not increasing in the watersheds with increasing runoff, it was established that the land-use changes was the major driving factor behind the change in hydrological regime over the agricultural watersheds. It was also established that the bias-correction of the climate projections using quantile-mapping techniques was able to improve the predictive skills of the projections. An exploration of bias-corrected future climate data established that Illinois will experience an increase in both temperature and precipitation in near and far future. By forcing the hydrological model of Embarras watershed with bias-corrected climate projections, it was observed that climate change will drive an increase in surface runoff and tile runoff, and consequently, nutrient transport from the tile drains. An increase in corn yield was also predicted under various scenarios. Thus, the nexus between the climate-water-food was explored in this study that helped us analyze the impacts of global warming on these three components of the nexus in the recent past and the future.U of I OnlyAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD syste