The water quality of a lake is a reflection of the condition and types of human activities in the surrounding watershed. Residential development and agricultural practices increase both surface runoff and nutrient sources which influence lake productivity. This report introduces GIS methodologies which can evaluate aspects of land use types in relationship to nonpoint sources of phosphorus loading to lakes. Lake drainage basins were delineated by on-screen digitizing with reference of topographic maps. Distributions of land use types were examined by the watershed boundary. The potential of a land use class to export a nutrient to a lake was represented by applying export coefficients in a GIS. Lake volume and average total phosphorus concentration were calculated by developing a Triangulated Irregular Network (TIN) in a GIS. Lastly as a management scenario, a buffer region was applied to represent riparian zones. The study shows that the occurrence of residential developments along shorelines potentially has a significant impact on lake quality. These areas would be priority targets for practices that decrease nutrient loading to lakes. Modeling Phosphorus (P) inputs to lakes is restricted by the omission of many ecological processes linked to physical land characteristics and lake cycling of P. However, initial examination of significant factors of phosphorus dynamics in a GIS provides insights into the influence of landscape features, and can aid in prioritizing management strategies.