Modeling stream discharge and nitrate loading in the Iowa-Cedar River basin under climate and land use change

Climate change manifests not merely as global warming; the latter term only starts to describe the impact of human activities on the planet. Extreme floods and droughts are another facet of climate change that are becoming accepted in the scientific discourse as not just independent events, but part of a growing trend. Naturally, different locales will weather different effects under climate change and how those effects emerge depend on how humans shape and use their land. Iowa has a fully developed agrarian economy infamous for releasing large amounts of nutrients into the waters of the United States. Nitrate, a major component and end-product of fertilizer application, is a threat to local water supplies, increasing the cost of drinking water treatment as the source water becomes more contaminated. Nitrate exiting Iowa eventually enters the Gulf of Mexico, accelerating algal blooms that subsequently suffocate the coastal waters deprived of oxygen. This research projects the future by building a computational model capable of simulating water quantity and water quality on the order of decades through the use of the Soil and Water Assessment Tool (SWAT). The model developed succeeded at simulating the past, a test that all models must pass. Applying scenarios created by leading institutions that study climate and land use change, the model foresees the possibility of greater flooding events and nitrate loads in a wetter and warmer future. No prediction is so exact to give the time and place of such events, but what SWAT can give is a sense of the average. An increase in the average implies an increase in the larger values of greater discharge and nitrate runoff.