Quantifying urban intensity in drainage basins for assessing stream ecological conditions

Three investigations are underway, as part of the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program, to study the relation be tween varying levels of urban intensity in drainage basins and in-stream wa ter quality, measured by physical, chemical, and biological factors. These studies are being conducted in the vicinities of Boston (Massachusetts), Sa lt Lake City (Utah), and Birmingham (Alabama), areas where rapid urbanizati on is occurring. For each study, water quality will be sampled in approxima tely 30 drainage basins that represent a gradient of urban intensity. This paper focuses on the methods used to characterize and select the basins use d in the studies. It presents a methodology for limiting the variability of natural landscape characteristics in the potential study drainage basins a nd for ranking the magnitude of human influence, or urbanization, based on land cover, infrastructure, and socioeconomic data in potential study basin s. Basin characterization efforts associated with the Boston study are desc ribed for illustrative purposes.