Using HSPF to Model the Hydrologic and Water Quality Impacts of Riparian Land-Use Change in a Small Watershed

Although land-use change in the riparian corridor can be a viable option in mitigating nonpoint source pollution, its impacts under different geographical scales have yet to be ascertained. The goal of this research was to quantify the hydrologic impacts of land-use change in the riparian zones of a subwatershed through the use of an integrated modeling approach. The Hydrological Simulation Program-Fortran model was adopted to develop a hydrologic and water quality model for the Upper Little Miami River basin, a headwater subwatershed in Ohio, USA. After calibration and validation, the model was used to predict the hydrologic and water quality impacts under various scenarios of buffer zones. Results indicated that the 60 m, 90 m, and 120 m riparian forest and wetland buffers were able to reduce the mean annual flow by 0.26 to 0.28%, nitrite plus nitrate by 2.9 to 6.1%, and total phosphorus by 3.2 to 7.8%. Wilcoxon signed rank test for paired data revealed significant differences between the base case (no change in land-use pattern) and scenarios of forest or wetland buffer zones, between pairs of different buffer widths, and between pairs of forest and wetland buffers within a single width level. By integrating environmental information and systems analysis, this study has demonstrated that HSPF is an effective tool to model nonpoint source pollution from riparian land-use changes, even in a small subwatershed with relatively minimal anthropogenic influences. The findings from this research may be useful in facilitating the development of management solutions.