Date of Graduation

Summer 2021


Master of Natural and Applied Science in Geography, Geology, and Planning


Geography, Geology, and Planning

Committee Chair

Robert Pavlowsky


Many of the environmental problems facing communities today stem from historical as well as present land use disturbances related to agriculture, urbanization, and resource extraction. It is important to evaluate a range of land use and soil effects on nonpoint source (NPS) pollution to fully understand land use-water quality relationships. The Ozark Highlands region has undergone significant phases of land use change throughout its settlement history and is actively developing today (2020). This study used nonpoint nitrogen (TN), phosphorus (TP), and sediment (TSS) yields predicted by the US EPA’s Spreadsheet Tool for Estimating Pollutant Loads (STEPL) model to evaluate human influences on water quality in different landscapes across the Missouri Ozarks during three time periods: pre-settlement (before 1820), peak agricultural land disturbance (between 1890 and 1950), and present-day (2019). Twelve watersheds of similar size were selected among three land use types: urban, forest, and agriculture, and within three different physiographic regions of the Ozark Plateau including the Springfield Plateau, Salem Plateau and St. Francois Mountains. Historical records and modern databases describing settlement, land use history and landscape characteristics were used to develop and conduct modeling for each sub-watershed. Present-day TN yields averaged 9.3-times and TP and TSS yields averaged 4.4-times higher than pre-settlement yields. However, pre-settlement yields were relatively variable with ranges among all sites of 6.4-times for TN, 5.8-times for TP, and 13- times for TSS. Natural nutrient and sediment loads reflected ecological soil and landscape factors, however, modern yields are most directly tied to land use variables. Anthropogenic contributions to total yields average 81% for TN, 67% for TP, and 56% for TSS.


nonpoint source pollution, land use, pre-settlement, anthropogenic, STEPL, Ozark Highlands, Missouri

Subject Categories

Environmental Health and Protection | Natural Resources and Conservation | Water Resource Management


© Tyler J. Pursley

Open Access