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ENVIRONMENTAL PROTECTION NRA National Rivers Authority South West Region ANNUAL CLASSIFICATION OF RIVER WATER QUALITY I 1990 December 1991 FWS/91/005 Author: R.J.Broome GORDON H BIELBY BSc Regional General Manager C V M Davies Environmental Protection Manager GLOSSARY RIVER REACH A segment of water, upttream from tampling point to the next sampling point. RIVER LENGTH River distance in kilometre*. RIVER QUALITY OBJECTIVE The. ttatement o k category o{, vote*. quality that a body of vote* thould match, utually in order to be. tatitfactory for ute at a fithery o k water tupply. COMPLIANCE ASSESSMENT A pKocedure applied to the. retult* of a monitoKing progKamme to determine, whether ok not a water hat met it* agreed Quality ttandard. QUALITY STANDARD A level of a tubttance o k any calculated value, of a meature of water quality, which mutt be met in order to protect a given ute of a water body. The ttandard it expretted at a pairing of a tpecific concentKation o k level of a tubttance with tummaKy ttoXittict tuch at a percentile o k maximum. 95 PERCENTILE STANDARD A level of wateK quality, utwJULy a concentration, which mutt be achieved fOK cut leatt 95% of the time. 5 PERCENTILE STANDARD The amount of oxygen dittolved in water. Oxygen it vital foK life, to itt meatUKement it important, but highly variable, tett of the 'health* of a water, it it uted to clattify watert. BIOLOGICAL OXYGEN DEMAND Thete are meaturet of the amount of oxygen (ATU) contumed in water, utually by organic pollution. The timple BOV value can be mitleading becaute much more oxygen it taken up by ammonia in the tett than in the natural water.
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