Essex Rivers Hub

This catchment consists of the river Crouch and Rettendon Brook, which flows into the Crouch Estuary. The total length of the Crouch is 15km and is split into three sections; upper Crouch, Crays Hill to Wickford and downstream of Wickford. The length of Rettendon Brook is 5km.

The Water Framework Directive classification for the River Crouch is moderate for the upper and downstream sections but this deteriorates slightly to poor in the middle section. Retterdon Brook is classified as moderate. All sections of the Crouch are failing for aquatic invertebrates and phosphates. In the upper Crouch Aquatic Invertebrates are classified as bad, in the middle section the classification improves slightly to poor but degrades to bad in the downstream section. For phosphates the upper Crouch is classified as poor but this reduces to bad in the middle and downstream sections. The upper section is also failing for dissolved oxygen and ammonia, which are both classified as moderate, and the middle section is also failing for diatoms (plants not visible to the naked eye). The only reason that Rettendon Brook is failing is because one of the mitigation measures are not in place. This measure is to put in place appropriate channel maintenance strategies that minimise disturbance to the channel bed and margins. The next step is to determine if this is still necessary and put in place so this water body can be classified as good or high.

All water bodies within the catchment have good flows and the whole of the Crouch has good morphology meaning the channel has natural features and good in channel habitats. Fish populations are doing well in the upper and middle sections of the Crouch and are doing particularly well in the middle section. Dissolved oxygen levels are high and ammonia levels are low in the middle and downstream section of the Crouch.

Phosphates are a problem throughout the River Crouch. In the upper section the sources have been identified as overflows from the sewage network, trade and private rural residential discharges, misconnections, runoff from agricultural land and roads and low flows. In the other 2 sections the exact sources have not be determined but it is suspected that the causes will be similar. Further investigation is needed to determine the exact sources throughout the water body. Once the exact sources have been determine actions to combat phosphate levels include working with water companies to reduce the impact of the sewage network and investigation misconnections, review discharge permits for businesses and private residences, visit land owners and advise on changes to land management to reduce their impact. Sustainable Drainage Systems (SuDS) should be considered to deal with some point pollution sources such as road run off and drainage ditches.

Aquatic Invertebrate populations are lower than expected throughout the River Crouch and this is partially linked to the issues identified for phosphates but lack of suitable habitat is also a major issue. More investigation is needed to determine the exact areas of concern and also work with landowners to make them aware of the riparian habitats that are required to improve the invertebrates' populations. Good buffer strips along the river edge would be a great start in improving this. In the downstream section the non-native invasive signal crayfish is also impacting on invertebrate levels by altering habitats, however no suitable method has been developed to tackle this invasive species.

It is important to note, however, that as part of their ongoing efforts to prevent the pollution of river water, the Environmental Agency considers the presence of certain pesticides and herbicides in this catchment, to be an issue of concern and must therefore be carefully managed through Safeguard Zone Action Plans to protect raw water sources used for drinking water.

  • Metaldehyde - An organic pesticide used against gastropods in both household and agricultural settings. It is mildly toxic when consumed by other organisms, especially predators of gastropods (hedgehogs, frogs, wild birds), and has been linked to their decline. Read more.
  • Carbetamide and propyzamide - these are herbicides used for winter oilseed rape and winter bean fields which target various annual grasses and broad-leaved weeds. They pose no known risk to mammals, birds and bees but are highly toxic to aquatic organisms.

Local water companies will continue to strive to abide with EU regulations as studies have shown that metaldehyde, carbetamide and propyzamide pose a very low risk to human health in low doses.

Dissolved oxygen and ammonia are also failing elements for the upper section of the Crouch. Both of these were previously rated as high so the data needs to be analysed and more investigations made to ensure these new results are correct. If they are, the reason for the drop in levels for dissolved oxygen and rise in levels of ammonia needed to be investigation to determine the cause.

Diatoms are a failing factor in the middle section of the Crouch but more investigation is needs to determine the cause for this.

 

 

 

 

 

 

 

 

Website key stakeholders:

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Design by LTD Design Consultants and build by Garganey Consulting based on an original concept by Herts and Middlesex Wildlife Trust