scales ranging from single rivers and watersheds (Duff et al., 2008) to larger basins and aquifer systems, and finally to the entire nation (Lapham et al., 2005; USGS, 2008). Most NAWQA studies are conducted in systems that cross political boundaries (e.g., Alexander et al., 2008) and over time scales that range from short term (days to months) to years (Van Metre and Mahler, 2005) and decades (Mahler et al., 2006). NAWQA continuously and consistently collects and interprets data over time scales that are relevant to hydrogeologic processes and the impact of human activities on them. Studies mentioned in earlier sections have benefited from the enhanced spatial (e.g., urban stream studies) and temporal (e.g., principal aquifer studies) perspective. NAWQA is uniquely positioned to carry out complex, interdisciplinary work at scales that are not possible to achieve by individual academic or government scientists.
NAWQA has achieved a national water-quality assessment. This judgment is based on the committee’s review of NAWQA achievements (Chapter 3), stakeholder assessments of the program heard in testimony, information contained in the NAWQA Science to Policy Management document (USGS, 2010), and the results of two NAWQA Customer Satisfaction Surveys (mentioned in Chapters 4 and 5). The committee concludes that in Cycles 1 and 2, NAWQA provided a successful national assessment of U.S. water quality, in accordance with the mission of a national water-quality assessment program.