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Geographic information systems; Water-supply; Runoff


ABSTRACT-We evaluate three data handling methods for use in a GIS analysis of land-cover change impacts on runoff. A universe of 2560 point samples is analyzed to provide runoff calculations that would se1:7e _as a comparison base to evaluate different attribute logic systems. The attribute logics ~e evaluate are two va~1at1ons of tag and one of count. We chose a two by five mile area of Dakota County, Mmnesota as the test site, and prepared raster GIS maps of soil hydrologic groups and two plausible land covers. The count 1:1~thod for handling the generalization of data produced results that were substantially closer to the charactenst_1cs of the universe than either of the tag approaches. To minimize error in assessment of water resources with a GIS, analysts should start with primary data, control all phases of data manipulation, and use count methods to abstract large-area data.

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