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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.