The flow paths of the ground water in the watershed were determined using nontoxic dyes as tracers. The dye traces helped to better define the individual subwatersheds of the greater Spring Mill Lake watershed. Incorporating the subwatershed information into the GIS made it possible to calculate the percent of the total watershed represented by each subwatershed. Better definition of the subwatershed areas makes it easier to employ best land management practices and to restrict the impact of any chemical spills or sediment transport.