Book excerpt: Groundwater has long been an object of intense scrutiny. Only recently have methods become available that permit ecologists, hydrologists, and environmental scientists to assess the biotic and abiotic status of these all-important aquifers. - The dynamics of water movement through complex subterranean ecosystems - The biological organization and the factors that constrain these ecosystems - Alluvial and karst ecosystem functions - Contamination, management, and remediation