The US Geological Survey collects and disseminates, in written and digital formats, groundwater and surface-water information related to the tidal and nontidal wetlands of the United States. This information includes quantity, quality, and availability of groundwater and surface water; groundwater and surface-water interactions (recharge-discharge); groundwater flow; and the basic surface-water characteristics of streams, rivers, lakes, and wetlands. Water resources information in digital format can be used in geographic information systems (GISs) for many purposes related to wetlands. US Geological Survey wetland-related activities include collection of information important for assessing and mitigating coastal wetland loss and modification, hydrologic data collection and interpretation, GIS activities, identification of national trends in water quality and quantity, and process-oriented wetland research. -Author