promised the water quality of the Everglades ecosystem in Florida (NRC, 2008a). The evaporation of water used to irrigate soils in arid western landscapes has caused salinization of western soils and agricultural yields (Schoups et al., 2005).

Prior pervasive surface-water and groundwater contamination of waters in the United States led to the Clean Water Act of 1972,2 the Safe Water Drinking Act of 1974,3 and other legislation dealing with water quality. Fortunately, the nation’s community water treatment infrastructure remains robust enough to ensure potable, high-quality tap water from rural areas to cities, despite remaining contamination in some places (Moran et al., 2004, 2005, 2007). But, in rural areas, many shallow aquifers no longer are used for drinking water supplies because of nitrate and bacterial contamination originating from agricultural practices and septic systems (Embrey and Runkle, 2006; Nolan and Hitt, 2006). Furthermore, in the north central and northeastern United States, the accumulation of millions of tons of road salt in the unsaturated soil threatens salinization of surface water and shallow groundwaters (Kaushal et al., 2005). Despite these problems, water quality in the United States remains high compared to many other parts of the world, but maintaining this high water quality for human and ecosystem health and prosperity is critical.

Established in 1879, the U.S. Geological Survey (USGS) has a distinguished history of leadership, serving the nation by providing scientific data to describe and understand Earth systems and unbiased assessments to facilitate management of the nation’s natural resources. Hydrologic research and hydrologic data collection and analyses are performed through the USGS Water Mission Area, one of six broad earth science mission areas around which USGS is organized: Energy and Minerals, and Environmental Health; Climate and Land-Use Change; Ecosystems; Natural Hazards; Core Science Systems; and Water.4 The administrative structure of water-related activities at the USGS has evolved throughout the history of the agency, yet the mission has remained constant: “to provide reliable, impartial, timely information needed to understand the nation’s water resources.”

Because USGS is a science agency with no regulatory or management responsibilities, the Water Mission Area (along with the entirety of the agency) has been widely recognized as a source of unbiased scientific information and hydrologic data. USGS research, studies, and data are used by other


2 Public Law 92-500, the Federal Water Pollution Control Act, or Clean Water Act, is the principal federal law governing contamination of the nation’s waters.

3 Public Law 93-523, the Safe Drinking Water Act, is the principal federal law intended to ensure safe drinking water for the public and applies to every public water system in the United States.

4 The Office of Science Quality and Integrity is tasked with improving and monitoring the quality of USGS science conducted by the six mission areas.

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