System for ClassifyingRiver quality can be measured and classified in different ways. Chemical analysis of water usually concentrates on biological oxygen demand (BOD) , dissolved oxygen (DO) and ammonia (NH3). These measures form the basis of the National Water Quality Classification Description Class Current Potential Use Good 1a Water of high quality suitable for potable supply abstractions; game or other high class fisheries; high amenity value. 1b Water of less high quality than class 1a but usable for substantially the same purposes. Fair 2 Waters suitable for potable supply after advanced treatment; supporting reasonably good coarse fisheries; moderate amenity value. Poor 3 Waters which are polluted to an extent that fish are absent or only sporadically present; may be used for low grade industrial abstraction; considerable potential for further use if cleaned up. Bad 4 Waters which are grossly polluted and are likely to cause a nuisance. Water Quality in Kirklees Compared with Yorkshire and England and Wales (1991) % total length of stream
Biological surveys recording the character of aquatic invertebrates can also be used to classify river quality. B1a the aquatic life indicates no pollution |