Ecological Indicators (Feb 2021)
Modeling nutrient release with compiled data in a typical Midwest watershed
Abstract
There is a critical need for an easy-to-adopt approach to estimate how different land use and management practices affect regional nutrient release into water bodies. As a typical agriculture dominated watershed in the Midwest, Indiana’s White River Watershed has observed large amounts of nutrient release from diffusive sources. This situation will likely worsen with population growth, climate change, and land use change.In this study, we integrated land use change scenarios, experimental data compiled from literature, and an easy-to-adopt nutrient simulation model to examine the effects of land use on nutrient load and delivery, and identify the sensitive areas of nutrient release in the White River Watershed. Nutrient Delivery Ratio (NDR) model and the Scenario Generator tool within the InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) ecosystem modeling framework, were adopted in this study, due to its capacity for scenario-based assessments and the simplified nutrient load and delivery functionality. Region-specific nutrient export coefficient values were compiled from literature and applied to model nutrient load and delivery in the White River Watershed, and the model was loosely calibrated with existing water quality monitoring databases.Results showed that the agricultural area releases more nutrients per unit area, while the forest area releases much less nutrients per unit area. Urban area is more sensitive to nitrogen release than phosphorus. Under the AgExpansion scenario, total nitrogen and phosphorus release would be 2.1% and 2.6% higher than the current situation, while under the Pre-settlement scenario, total nitrogen and total phosphorus release would decrease by 73.7% and 88.0%. The approach developed is helpful for watershed protection that avoids computation of complex social and biophysical processes, to inform and guide conservation practices by revealing areas with the greatest effects on nutrients in streams under different land use scenarios. The experiment database that was compiled could serve as the basis of similar studies in the future. The approach will be beneficial to local community and may easily be applied to other agriculture dominate Midwest regions.
