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INTEGRATION OF LANDSAT DATA, GIS, AND AGNPS IN ASSESSMENT OF LAND 
USE IMPACT ON WATER QUALITY 
Chansheng He 
Department of Geography 
Western Michigan University 
Yung-Tsung Kang and Changan Shi 
Institute of Water Research 
Michigan State University 
ABSTRACT 
This study integrates AGNPS, an Agricultural Nonpoint Source Pollution Model, with 
LANDSAT imagery, and GRASS (Geographic Resource Analysis and Support System) to 
evaluate the impact of land use/cover change on water quality in the Saginaw Bay basin of 
Michigan. LANDSAT data of 1984 and 1992 were used to derive the land cover classification. 
The accuracy of the classification was assessed by field verification and by scanning the 35mm 
slides of the Agricultural Stabilization and Conservation Service. GRASS and GRASS 
WATERWORKS, a geographic information system and a hydrologic modeling tool box, 
respectively, were used to generate parameters needed for AGNPS from digital data of soil, land 
use, water features, and topography. AGNPS was used to estimate changes in the amounts and 
distribution of erosion, sediment, nitrogen (N) and phosphorus (P) as a result of land use/cover 
change in the watershed between 1984 and 1992. The results indicate that implementation of 
conservation programs such as Conservation Reserve Program (CAP), and best management 
practices such as crop residue cover and disk tillage has led to the reduction in sediment loading, 
and nutrient runoff in the study area. However, some areas in the watershed are still vulnerable to 
erosion and additional effort needs to be taken to minimize the erosion and sedimentation in these 
areas.