Essex Rivers Hub

River Blackwater 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

Floating Pennywort has been most recently recorded on this water body in 2011 and 2012 Floating Pennywort covers the surface of the river, blocking out natural light and causing the plants below to die. The dead plants then rot down, removing the oxygen from the river. Floating Pennywort also causes trouble for boats, making the river very difficult to navigate.

Eradication of floating pennywort can only be successful through spraying. It spreads very quickly and just small live fragments can allow it to take hold again. If you see this plant species then please alert us as soon as possible.

 

Water Fern has been most recently recorded on this water body in 2012. This plant covers the surface of the river, blocking out natural light and causing the plants below to die. The dead plants then rot down, removing the oxygen from the river.

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.

 

Japanese Knotweed has been most recently recorded on this water body in 2013. 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.

 

Signal Crayfish have been most recently recorded on this water body in 2002 and 2008 Signal Crayfish cause changes to the natural bankside habitat and also out-compete our native crayfish.

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.

 

Turkish Crayfish have been most recently recorded on this water body in 2002. 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.

 

Chinese Mitten Crab have been most recently recorded on this water body in 2013. Mitten crabs cause changes to the natural habitat as they modify the river banks, this can make them unsuitable for our natural species.

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

 

 Giant Hogweed has been most recently recorded on this water body in 2013. 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.

 

American Mink have been most recently recorded on this water body in 2009 and 2011. 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.

 

Himalayan Balsam has been most recently recorded on this water body in 2013. This pretty plant, with pink flowers, is fast growing and hardy. It covers river banks and shades out native plants. In the winter, Himalayan Balsam will die down, leaving bare banks that are susceptible to erosion.

Himalayan Balsam can be removed easily by pulling it from the ground (including the root), snapping the basal stem and then leaving it in a pile to rot down. If you would like to get involved in pulling this invasive species, or would like to organise a work party, then please let us know through the contact us page.

 

The non-native invasive Signal Crayfish as well as the native White-clawed Crayfish are found in this water body.

There is currently no affective method to control the invasive Signal Crayfish. Continued monitoring of the native crayfish will determine if it is being impacted by the invasive species.

Multiple mitigation measures were put in place in order to improve the morphology of this water body which is currently classified as 'moderate'. These mitigation measures were not taken forward.

Removal of hard bank reinforcement / revetment, or replacement with soft engineering solution

Increase in-channel morphological diversity

Bank rehabilitation / reprofiling
Improve floodplain connectivity

Structures or other mechanisms in place and managed to enable fish to access waters upstream and downstream of the impounding works.

Preserve and where possible enhance ecological value of marginal aquatic habitat, banks and riparian zone

Operational and structural changes to locks, sluices, weirs, beach control, etc.

Flow has been investigated in this waterbody, but its effect on the ecological status is yet to be determined.

Determine the effect of flow on the ecological status of this water body.

This water body has developed problems with phosphate levels which contribute to its overall rating as poor. Unfortunately there is no data to suggest where these problems are originating from. The amount of phosphate fluctuates across the water body, but is likely to be causing this water body to fail for its macrophyte level too.

The River Blackwater failed tests for 'Annex 10' chemicals as traces of aromatic hydrocarbons were detected. These hydrocarbons are usually found in petrol, other fuel sources or when burning. Sewage treatment works have been identified as possible sources for these chemicals too.

Carry out further investigation in order to determine the source of pollutants and take the action required to solve the problem.

Determine the sources of the Annex 10 Chemicals detected within this water body.

This water body has developed problems with phosphate levels which contribute to its overall rating as poor. Unfortunately there is no data to suggest where these problems are originating from. The amount of phosphate fluctuates across the water body, but is likely to be causing this water body to fail for its macrophyte level too.

Carry out further investigation in order to determine the source of pollutants and take the action required to solve the problem.

  

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