Essex Rivers Hub

River Colne downstream of Doe's Corner Pressures

The table below shows the current pressures that this waterbody faces and the solutions that could be put in place to solve these problems. You can learn more about some of these pressures and solutions on the Environment Agency Catchment Data Explorer or you can contact us to find out more.

PRESSURES

SOLUTIONS

Turkish Crayfish have been most recently recorded on this water body in 2007 and 2008. Turkish Crayfish cause changes to the natural bankside habitat and also out-compete our native crayfish. They are fierce predators and can completely change fish and invertebrate communities so that they are no longer in their natural state.

There is currently no known solution to the invasion of Turkish Crayfish, regular monitoring is needed to ensure a strategic approach when a solution has been identified.

 

Signal Crayfish have been most recently recorded on this water body in 2010 and 2011. Signal Crayfish cause changes to the natural bankside habitat and also out-compete our native crayfish. They are fierce predators and can completely change fish and invertebrate communities so that they are no longer in their natural state.

There is currently no known solution to the invasion of Signal Crayfish, regular monitoring is needed to ensure a strategic approach when a solution has been identified.

 

New Zealand Pigmy Weed has been most recently recorded on this water body in 2008. This plant forms dense mats in waterways, increasing the likelihood of flooding and also out-competing native species.

 This plant can be mechanically removed, but this would only be a short term solution. Chemical eradication is possible and if done correctly can be very effective. After eradication it is important to monitor sites to ensure that it does not take hold again.

 

American Mink have been most recently recorded on this water body in 2003. American Mink cause a wide range of problems on a river, including playing a large part in the local extinction of many natural species such as water voles and kingfishers.

In order to eradicate mink, they must be trapped and dispatched. Trapping must be done catchment wide as mink can travel large distances. It is important that there are enough people involved in a trapping project to ensure that the traps can be checked regularly. Monitoring mink, water vole and otter presence on your river can also help us when planning eradication programmes.

 

Giant Hogweed has been most recently recorded on this water body in 2015. This plant has been in the news a lot more recently due to the horrific burns that its sap can give the skin. This invasive plant is so large that it is able to shade out other native plants.

Giant Hogweed MUST be removed by a professional ONLY. The plant is sprayed off and then removed in a safe manner. If this plant has already been removed from this waterbody then please let us know, if it is spreading further then get in touch.

 

Japanese Knotweed has been most recently recorded on this water body in 2015. This plant not only shades out native plants, but also causes serious damage to buildings.

Japanese Knotweed can be removed by spraying or injecting its roots with pesticides, this takes time to kill the plant, but it is effective. Just digging up this plant is, unfortunately, not enough.

 

The water body is classified as heavily modified. These modifications are in place to prevent flooding.

Where possible, obsolete structures will be removed and others adapted to allow fish passage.
Increase in channel habitat and structural diversity.

The water body has been classified as heavily modified.
There are also significant barriers to fish passage such as the weir in Halstead.

Remove obsolete structures and look at those that must remain to see what measures can be taken to enable fish to migrate up and downstream.

Flow has a seasonal variation with the lowest flows at the end of summer/beginning of autumn. It needs to be determined if abstraction is having negative impact at these times.

A lot of work has been done to determine if abstraction (mainly for water supply) is having an impact and to ensure this is tackled. However more data needs to be collected for some abstraction points. 

Phosphate levels are high leading to a classification of poor.

Further investigations needed to determine why levels are high and if there are any point source causes.

Phosphate levels are high leading to a classification of poor.

Further investigations needed to determine why levels are high and what the sources are.

  

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