MULTIVARIATE CLASSIFICATION OF SMALL ORDER WATERSHEDS IN THE QUABBIN RESERVOIR BASIN, MASSACHUSETTS

A multivariate approach was used to analyze hydrologic, geologic, geog raphic, and water-chemistry data from small order watersheds in the Qu abbin Reservoir Basin in central Massachusetts. Eighty three small ord er watersheds were delineated and landscape attributes defining hydrol ogic, geologic, and geographic features of the watersheds were compile d from geographic information system data layers. Principal components analysis was used to evaluate 11 chemical constituents collected bi-w eekly for 1 year at 15 surface-water stations in order to subdivide th e basin into subbasins comprised of watersheds with similar water qual ity characteristics. Three principal components accounted for about 90 percent of the variance in water chemistry data. The principal compon ents were defined as a biogeochemical variable related to wetland dens ity, an acid-neutralization variable, and a road-salt variable related to density of primary roads. Three subbasins were identified. Analysi s of variance and multiple comparisons of means were used to identify significant differences in stream water chemistry and landscape attrib utes among subbasins. All stream water constituents were significantly different among subbasins. Multiple regression techniques were used t o relate stream water chemistry to landscape attributes. Important dif ferences in landscape attributes were related to wetlands, slope, and soil type.