viii, 72 pages : illustrations (some color), color maps ; 28 cm
OCLC
ocm50617059
"National Water-Quality Assessment Program"--P. [1] of cover.
Includes bibliographical references (pages 66-67).
Also available via Internet from the USGS web site. Address as of 10/9/02: http://water.usgs.gov/pubs/wri/wri024142/pdf/WRIR02-4142.pdf ; current access is available via PURL.