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Design of the National Water-Quality Assessment Program
註釋Assesses the status of & trends in the quality of America's ground- & surface-water resources The Occurrence & Distribution Assessment component characterizes broad-scale water-quality conditions in relation to major containment sources & background conditions in each study area. The surface-water design focuses on streams. The ground-water design focuses on major aquifers, with emphasis on recently recharged ground water associated with human activities.