Modeling distribution of point and nonpoint sources pollution loadings in the saginaw bay watersheds, Michigan

Abstract

This study involves developing a physically based, spatially-distributed water quality model to simulate spatial and temporal distributions of point and nonpoint sources in the Saginaw Bay Basin, Michigan. Databases of point sources including combined sewer overflows (CSOs) were acquired from the governmental agencies to map the occurrences and magnitude of the CSOs. Multiple databases of meteorology, land use, topography, hydrography, soils, and agricultural statistics were used to estimate nonpoint source loading potential in the study watersheds. Results indicate that point sources from municipalities, industrial sectors and business entities contribute approximately 25% of the total phosphorous load to Saginaw Bay. While total amount of nutrients (N and P) from animal manure and fertilizer applications and atmospheric deposition declined in the Saginaw Bay Basin, fertilizer applications in non-farmland increased significantly.