THE ROLE OF SAMPLE-SURVEYS FOR MONITORING THE CONDITION OF THE NATIONS LAKES

In order to meet a growing need to determine the condition of the nati on's ecosystems and how their condition is changing, the U.S. Environm ental Protection Agency (EPA) developed EMAP, the Environmental Monito ring and Assessment Program. A common survey design serves as the foun dation on which to base monitoring of status and trends among diverse ecosystem types. In this paper, we describe the need for a statistical ly based survey design, briefly summarize the basic EMAP design, descr ibe how that design is tailored for the selection of a probability sam ple of lakes on which to make measurements of lake condition, and illu strate the process for selecting a sample of lakes in the northeastern United States. Finally, we illustrate how measurements taken on the s ample of lakes can be summarized, with known uncertainty, to describe the condition of a population of lakes.