National Water-Quality Assessment (NAWQA) Project

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Featured Studies
Special studies on source-water and drinking-water quality
Surface-water intakes
General Information

Groundwater-Quality Trends

Home National Results and Maps Background Factors Affecting Trends Simulation and Forecasting Data Trends Publications

Featured New Reports

report thumbnailUsing groundwater age distributions to understand changes in methyl tert-butyl ether (MtBE) concentrations in ambient groundwater, northeastern United States


report thumbnailPesticides in Groundwater of the United States: Decadal-Scale Changes, 19932011

Interactive Mapping Tool

This mapper shows how concentrations of pesticides, nutrients, metals, and organic contaminants in groundwater are changing during decadal periods across the Nation.


Groundwater-quality monitoring data collected by NAWQA from many regions of the United States are being synthesized into a national assessment of groundwater-quality trends. Between 1988 and 2000, NAWQA completed groundwater-quality assessments in 51 study areas across the United States. During 2001, NAWQA began resampling many of those well networks on a near-decadal timeframe to determine if groundwater quality has changed over time. A well network is typically 20-30 randomly selected wells designed to examine groundwater quality in a region; in some cases well networks are designed to represent specific land-use practices such as agricultural or urban. To date (2012), 1,235 wells in 56 well networks have been resampled on a near-decadal time period (Lindsey and Rupert, 2012; Rupert, 2005). NAWQA will continue to periodically resample wells.


Featured Interactive Map: Changes of nitrate concentrations in groundwater of the United States


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