This coverage contains information about estimates of current
acid-base status of surface waters in National Surface Water Survey
regions in the conterminous U.S., as reported in the National Acid
Precipitation Assessment Program's 1990 Integrated Assessment Report
(NAPAP, 1991). It was created by the Environmental Protection Agency's
Clean Air Markets Division (CAMD) for use with their GIS in ... helping
them to determine the effects of emissions (i.e. sulfur and nitrogen)
on natural resources.
The National Surface Water Survey (NSWS) was conducted in areas of the
United States where lakes and streams sensitive to acidic deposition
were known to exist. Adverse aquatic effects from acidic deposition
are unlikely in areas of the United States that were not sampled in
the NSWS, since surface waters in these areas generally have high acid
neutralizing capacity (ANC), with the possible exception of parts of
the Coastal Plain, in the Southeast.
The NSWS is the best data source for a national assessment of the
aquatic effects of acidic deposition, because regional comparisons can
be made on the same well-defined population of lakes and streams. The
NSWS estimates of acidic surface waters given here refer to those with
ANC less than or equal to zero.
This coverage was created in ArcView using information from the
National Acid Precipitation Assessment Program's 1990 Integrated
Assessment Report by digitizing the boundary areas for the Acidic
[Summary provided by the EPA.]