Threats to Lincolnshire's Chalk Streams

Left: Cow drinking from cattle drink on the Great Eau Right: Mink, non-native species

Chalk streams are internationally rare habitats unique to the south and east of England and Normandy in France. Unfortunately, this habitat has been neglected by historical land use practices with the moving and straightening of channels to create boundaries for villages, irrigation for arable crops and to power water mills.  Even today the chalk streams and their wildlife are still under threat from:

  • Abstraction - drinking water supply, industry, fish and watercress farms, irrigation. Resulting in low flows, reduced dilution of pollutants, sedimentation, excess algal growth, loss of current-loving species, entrapment of wild fish.

Sediment Great Eau

  • Effluent discharge - sewage, industrial effluent, fish and watercress farms. Resulting in introduction of endocrine disruptors;  increased temperatures;  organic , nutrient and toxic pollution; loss of species;  excess algal growth and reduced population size.
  • Agriculture - Livestock: Bank damage, polluted runoff (organic matter, nutrients, sediment).  Arable: Drainage, polluted runoff (nutrients, herbicides, endocrine disruptors, sediment).  Resulting in damage to aquatic and wetland habitats and sensitive species, reduced water quality, accelerated runoff and reduced groundwater discharge.
  • Flood defence, land drainage, inappropriate level control - Channel and bank engineering, weed cutting, dredging, hatch operation. Resulting in damage to aquatic and riparian species and habitats.
  • Development, Urban development - construction, polluted runoff (e.g. oils, sediment, heavy metals). Resulting in habitat loss, poor water quality, higher water demand, obstruction to fish passage.
  • Fisheries management - weed cutting, riparian management, Fish stocking and removal fish community change. Resulting in habitat loss, reduced flow velocity and gravel scour and risk of spreading fish and other diseases.
  • Recreation – an excess of walking, canoeing, boating. Resulting in disturbance.
  • Non-native and invasive species - escape and spread of farmed fish, crayfish, mink, non-native plants (e.g. Himalayan balsam); localised overgrazing of water-crowfoot by mute swans and cattle. Resulting in loss of native species and habitat.



Signal Crayfish River Bain


Mink Raft



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