In the mid-1970s a flurry of research and assessment activity began on nonpoint source (NPS) pollution. Much of the activity was driven by legislative requirements, particularly Section 208 of the Clean Water Act which required states to identify nonpoint sources of pollution and develop feasible procedures and methods to control these sources. Unfortunately, response to the law was piecemeal--most states lacked a logical and useful spatial (geographical) framework to put the results in a meaningful environmental perspective. Spatial frameworks can have a profound influence on the effectiveness of the research, assessment, and management of many aquatic resource problems, particularly nonpoint source pollution. The authors believe that spatial frameworks based on ecological regions can often be more useful for assessing the health of aquatic systems than frameworks based only on hydrologic units, drainage basins, or administrative or political units. Their objective is to demonstrate the usefulness of the frameworks and approaches, and show the relative ineffectiveness of hydrologic units with examples at national, regional, and local scales.