Good quality: river reaches with nutrient-poor water, low levels of organic matter; saturated with dissolved oxygen; rich invertebrate fauna; suitable spawning ground for salmonoid fish. Fair quality: river reaches with moderate organic pollution and nutrient content; good oxygen conditions; rich flora and fauna; large fish population. Poor quality: river reaches with heavy organic pollution; oxygen concentration usually low; sediment locally anaerobic; occasional blooming of organisms insensitive to oxygen depletion; small or absent fish population; periodic fish kill. Bad quality: river reaches with excessive organic pollution; prolonged periods of very low oxygen concentration or total deoxygenation; anaerobic sediment, severe toxic input; devoid of fish.
Fair quality: river reaches with moderate organic pollution and nutrient content; good oxygen conditions; rich flora and fauna; large fish population. Poor quality: river reaches with heavy organic pollution; oxygen concentration usually low; sediment locally anaerobic; occasional blooming of organisms insensitive to oxygen depletion; small or absent fish population; periodic fish kill. Bad quality: river reaches with excessive organic pollution; prolonged periods of very low oxygen concentration or total deoxygenation; anaerobic sediment, severe toxic input; devoid of fish.
Poor quality: river reaches with heavy organic pollution; oxygen concentration usually low; sediment locally anaerobic; occasional blooming of organisms insensitive to oxygen depletion; small or absent fish population; periodic fish kill. Bad quality: river reaches with excessive organic pollution; prolonged periods of very low oxygen concentration or total deoxygenation; anaerobic sediment, severe toxic input; devoid of fish.
Bad quality: river reaches with excessive organic pollution; prolonged periods of very low oxygen concentration or total deoxygenation; anaerobic sediment, severe toxic input; devoid of fish.