Assessing the Relative and Combined Impacts of Future Land-Use and Climate Changes on Nonpoint Source Pollution

摘要

In this paper, we discuss the potential water quality impacts of future land-use and climate changes. The Little Miami River Basin was used as a case study. It is a predominantly agricultural watershed in southwestern Ohio (USA) that has experienced land-use modifications. We investigate the impacts on a suite of nonpoint source pollutants, including phosphorus, nitrate, sediment, pesticides/herbicides, and fecal coliform. Quantification of these impacts is important to our understanding of the magnitude of the adjustments that need to be made to current water resource allocations under future environmental conditions. Future land-use conditions in the watershed are derived from the existing future land-use development plans of the eleven counties comprising the watershed. Future climate changes are simulated using results from recent Global Circulation Models. The future hydrologic and water quality conditions were modeled using a continuous, long-term, watershed-scale hydrological model, SWAT (Soil and Water Assessment Tool). The model is first calibrated and validated based on existing monitoring data. The model is then used to quantify the changes in both water quality and quantity, which would occur under the projected future climate and land-use conditions. Preliminary results indicate that the eutrophication problem in the watershed is due to an overabundance of phosphorus; however, under future climate and land-use conditions, the total phosphorus concentration can decrease from 3.0 mg/L to 1.21 mg/L. This information is useful as it can be used to guide the development of future mitigation strategies in the watershed