Essex Rivers Hub

The Wid is the main water body in this catchment. The Wid has a total length of 30km and is split into 5 sections, which are Blackmore to Mountnessing, Mountnessing to Havering's Grove Brook, Havering's Grove Brook to Ingatestone, Ingatestone to Margaretting and Margaretting to River Can. There are two tributaries to the Wid and they are Chainbridge Tributary (6km long) and Havering's Grove Brook (6km long). Chainbridge Brook enters the Wid in the Blackmore, Mountnessing, Havering's Grove Brook area and Havering's Grove Brook itself enters the section marked as Mountnessing to Havering's Grove Brook.

Most of the water bodies within the catchment have a Water Framework Directive classification of moderate with the exception of the Wid from Blackmore to Mountnessing and Chainbridge Tributary which have a classification of poor. One of the main failing factors is phosphate with 6 of the 7 water bodies classified as poor. The only water not failing for this is Havering's Grove Brook, in fact the only reason this water body is failing is because one of the mitigation measures has not been put in place so hopefully this water body will be in good ecological status very soon. Another factor that is impacting several water bodies in the catchment are low aquatic invertebrate populations, which 4 water bodies' are failing for. The good news about this catchment is that all of the water bodies have good fish populations and good flows and most have good levels of dissolved oxygen and low levels of annex 8 chemicals.

Phosphate is a problem throughout the catchment and has been linked to point and diffuse source pollution, private and industry source, rural and urban runoff therefore there are lots of areas to tackle for this issue. In the Wid from Blackmore to Mountnessing and Margaretting to Can the exact cause of the failure is unknown so more investigation is needed here. Where the source has been identified then the next stage is to work with farms, households, industrial estates and sewage treatment works to determine how their impact can be reduced.

Aquatic Invertebrates populations are a failing factor on the Wid from Blackmore to Ingatestone and also for Chainbridge Tributary. From Blackmore to Havering's Grove Brook on the Wid the classification is poor however this improves to moderate from Havering's Grove Brook to Ingatestone and from Ingatestone to the Can there is no failure and the classification is good. The classification for Chainbridge Tributary is moderate. This suggests the greatest impact is in the upper reaches of this catchment. The reasons for failure are linked to sewage treatment works (especially between Blackmore and Mountnessing), agriculture runoff, urban runoff and the presence of the invasive Signal Crayfish. These failures seemed to be linked to phosphate levels as the same factors are causing the failures, therefore the solutions are the same. The only difference in this case is the Signal Crayfish; unfortunately there is no affective method to tackle this species at this time.

Diatoms (plants not visible to the naked eye) are a failing factor for Chainbridge Tributary and the Wid between Blackmore and Mountnessing, the rest of the Wid does not have an issue with these plants. The reason for failure in these two water bodies is currently unknown so more investigation is needed.

Ammonia is a failing element in two parts of the Wid, the areas affected are Blackmore to Mountnessing and Havering's Grove Brook to Ingatestone, on the positive side the area between Mountnessing and Havering's Grove Brook has low levels of ammonia. The rest of the Wid and its tributaries have low levels of ammonia also, therefore the problem is very localised. In both areas that have high ammonia, the levels have been linked to sewage treatment works so water companies need to look at this issue and determine how they can lower the level of ammonia they release.

Dissolved oxygen is generally good within the catchment, in fact only one area is failing for dissolved oxygen and that is the Wid between Blackmore to Mountnessing. The failure has been linked to seasonal variation which means that at times of year (summer to autumn) when flows are low and temperatures are high the levels drop significantly. The result of low flows means that the effluent that is entering the river from various discharges has less dilution potential and this is resulting in a lowering of the dissolved oxygen at that time. As aquatic invertebrate populations are also low in this section of the Wid dissolved oxygen levels may also be a factor in this. To reduce the problem, solutions need to be looked at to increase flow where possible.

The following mitigation measures are outstanding for this catchment:

  • Appropriate channel maintenance strategies and techniques - minimise disturbance to channel bed and margins

 

 

 

 

 

 

 

 

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