Water classification data
Scotland has an extensive network of rivers and streams. They
have substantial biodiversity, conservation and economic value, and
it is one of SEPA’s aims to protect and, where appropriate, improve
their quality. In order that progress is made in this task, SEPA
has built up an extensive monitoring network designed to represent
the quality of all significant waters. Thus, river lengths are
assigned the quality of a downstream monitoring point. For the
purposes of river length measurement, the smallest streams with
catchments of less than 10 km2 have been excluded, except where
they are the main source of a larger river, or they are
substantially polluted. This is in accordance with European
conventions, and avoids having to monitor small streams which may
seasonally dry up. The total length of rivers with a catchment area
of 10 km2 or more is 24,404km and SEPA’s efforts are focused here.
In 2003, about 800km of these rivers were considered to be of poor
quality or seriously polluted, with a further 2,400km of only
‘fair’ quality.