Acid mine drainage (AMD), along with acid rock drainage (ARD), is a problem of water quality that is common to rivers and lakes that receive water draining from mine sites. Although not usually viewed as a first-tier environmental problem, AMD is a critical water-quality issue around the world, affecting nations from the Far East to Europe and the Americas. In the United States it occurs in wide areas in the East as a result of coal mining. In the American West several hundred thousand abandoned hard rock mines have contaminated thousands of miles of streams and thousands of lakes. Sites, streams, and lakes that require attention number in the thousands, according to the Mineral Policy Center (1997), which estimates that the cleanup in the United States alone will cost more than $10 billion. Acid mine drainage also provides an object lesson in the complex relationships among...