was also smaller (mean catchment area = 64 km2) than
that of lakes (257 km2), because streams with catchments
>250 km2 were not included in the national stream
survey.
Water Chemistry
A single, midstream or midlake (approximately 0.5 m
depth) water sample was collected in autumn 2000. All
water chemistry analyses were done by the SWEDAC
(Swedish Board for Accreditation and Conformity
Assessment) certified laboratory at the Department of
Environmental Assessment, Swedish University of Agricultural
Sciences following international (ISO) or European
(EN) standards when available. ANC is a measure of
the buffering ability of lakes and streams against strong
acid inputs. This metric was chosen because it includes
humic substances and compensates for their natural variation,
i.e., the effect of acid deposition is more pronounced
than in other acidification indicators such as pH or sulfate
concentration.