Identifying Future Drinking Water Contaminants (1999) / Chapter Skim
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2 Emerging Drinking Water Contaminants: Overview and Role of the National Water-Quality Assessment Program
2 Emerging Drinking Water Contaminants: Overview and Role of the National Water-Quality Assessment Program
Pages 33-42
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From page 33... ...
NAWQA DESIGN The NAWQA program attempts to balance the unique assessment requirements of individual hydrological systems with a nationally consistent design structure that incorporates a multiscale interdisciplinary approach. The building blocks of the national assessment are investigations in major hydrological basins of the nation, referred to as "study units." The goal for the first phase of investigation in each study unit is to characterize, in a nationally consistent manner, the broad-scale geographic and seasonal distributions of water quality conditions in relation to the most significant contaminant sources and background conditions.
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From page 34... ...
First, the accumulation of consistent and comparable water quality assessments for some of the largest and most important hydrological systems of the nation will stand alone as a major contribution to our knowledge of regional and national water quality conditions. Second, the NAWQA national synthesis builds on and expands the findings from individual study units by combining and interpreting results from multiple study units together with historical information reported by the USGS and other agencies and researchers.
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From page 35... ...
. Emerging Drinking Water Cor'taminanis sampling designs for all three components rely on coordinated sampling of varying intensity and scope at integrator sites, which are chosen to represent water quality conditions of rivers in large basins that are commonly affected by complex combinations of land-use settings, and at indicator sites, which are chosen to represent water quality conditions of streams and smaller rivers associated with specific environmental settings.
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From page 36... ...
Some of the sites sampled on major rivers are close enough to water-supply withdrawals that they are reasonably representative of the source water used for drinking water, while others are in regions where groundwater or remote surface water sources are used for drinking water. Grour'dwater The national study design for groundwater focuses on water quality conditions in major aquifers and in recently recharged shallow groundwater associated with current and recent land uses: · Aquifer or "study unit" surveys assess the quality of water in the major aquifer systems of each study unit.
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From page 37... ...
Because of the nature of their design, some land-use studies were reclassified as both drinking water aquifers and shallow groundwater. Selection of Target Analytes The NAWQA program has selected a wide range of physical, chemical, and biological measurements to monitor in a nationally consistent manner.
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From page 38... ...
toxicity to freshwater aquatic organisms; (5) occurrence data for VOCs in groundwater, surface water, and drinking water; (6)
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From page 39... ...
and tissue for the study unit in relation to the national range observed across all 20 NAWQA study units and in relation to existing environmental standards and guidelines. National Synthesis: Pesticides in Surface Water and Groundwater Results from the first 20 study units during 1992 to 1996 include analyses of 76 pesticides and seven pesticide degradates in more than 8,000 samples of water from rivers, streams, and wells.
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From page 40... ...
Most concentrations are substantially below EPA drinking water standards, which were exceeded in less than 1 percent of the wells sampled. In streams, peak concentrations of several herbicides frequently occurred above EPA drinking water standards in some agricultural areas, but annual average concentrations, which are used for regulation, rarely exceeded standards.
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From page 41... ...
SUMMARY The NAWQA program provides information useful in identifying emerging contaminants in the nation's streams, rivers, and groundwater used for drinking water in several ways. First, NAWQA study units cover almost half of the conterminous United States and represent some of the largest and most important hydrological systems.
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From page 42... ...
This type of approach is essential for identifying emerging contaminants and changes in concentrations of contaminants in relation to changes in land- and water-use activities. Fourth, in addition to investigations of individual hydrological systems, national synthesis currently focused on pesticides, VOCs, nutrients, and trace elements helps to identify regional and national patterns in the occurrence and distribution of contaminants of concern and their relation to contaminant sources.
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