There are 20 water bodies in this operational catchment, including the whole of the River Chelmer, Stebbing Brook, Boreham Brook and Sandon Brook. The two primary sources of the Chelmer run to the north and to the west of the hamlet of Debden Green. One of the sources rises in Rowney Wood, on the hill to the west of Debden Green, only a few hundred metres to the south east of the source of the River Cam that heads north through Cambridge eventually emptying into The Wash.
The Chelmer rises near Thaxted & flows south east towards Chelmsford, where it joins a number of other significant tributaries including the River Can and River Wid. It is predominantly rural in nature until it reaches Chelmsford, where it is canalised through the city centre. Downstream of Chelmsford the river gives way to a canal which is popular for recreational boating. It is joined by the River Ter, one of the most natural and undisturbed rivers in the County, before joining the River Blackwater at Langford. The Chelmer supports a high quality fishery and is an important source of public drinking water.
13.8 miles of the River Chelmer is comprised of the Chelmer and Blackwater Navigation which conveys the water of the Chelmer and later the Blackwater from Chelmsford to the estuary. The Chelmer & Blackwater Navigation completed in 1797 largely follows the course of the River Chelmer and runs through a largely unspoilt part of rural Essex. It has a footpath along its full length and boating and paddling boarding are popular recreational activities. It was taken over by Essex Waterways Ltd in 2005. To find out more about the navigation, please visit
Chelmer & Blackwater Navigation – Inland Waterways.
The pressures for this waterbody are divided into categories: Diffuse Pollution, Fish Passage, Flow, Invasive Species, Physical Modification, and Point Source . Please click here to view these pressure descriptions in more detail.
American Mink have been most recently recorded on this water body in 2012. 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.
Giant Hogweed has been most recently recorded on this water body in 2014. 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.
Ammonia is classified as bad for this water body but information on the possible source is not available.
This water body has developed problems with phosphate, and dissolved oxygen levels which both contribute to its overall rating as moderate. Unfortunately there is no data to suggest where these problems are originating from, although diffuse agricultural pollution is suspected. Reduced oxygen levels are often common in summer months because of reduced river flows, higher water temperatures, increased oxygen demand due to increased biological activity and higher effluent proportions in watercourses.
Fish populations have decreased since 2009 which means that this water body is failing for fish. Specific reasons for this have not been identified although the low levels of dissolved oxygen and redundant structures (preventing fish migration) are likely to be contributing to the reduced populations.
Signal Crayfish have been most recently recorded on this water body in 2010. 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.
Giant Hogweed has been most recently recorded on this water body in 2014. 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.
American Mink have been most recently recorded on this water body in 2009. 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.
This water body has developed problems with phosphate, and dissolved oxygen levels which both contribute to its overall rating as moderate. Unfortunately there is no data to suggest where these problems are originating from, although point source from local sewage treatment works is suspected. Reduced oxygen levels are often common in summer months because of reduced river flows, higher water temperatures, increased oxygen demand due to increased biological activity and higher effluent proportions in watercourses.
This is classified as not high indicating there may be some issues with flow.
Himalayan Balsam has been most recently recorded on this water body in 2006. 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.
Phosphate levels in this waterbody are classed as poor. This is likely to be because of diffuse agricultural pollution as the majority of this waterbody is lined with agricultural based land.
The Sandon Brook gauging station has been assessed and it is confirmed to be a barrier to fish but not eels.
There are a number of water abstractions that take place on this waterbody that could impact the flow dynamics of the system. This waterbody has problems with its fish population; un-natural flows could be contributing to this.
American Mink have been most recently recorded on this water body in 2008. 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.
Signal Crayfish have been most recently recorded on this water body in 2012. 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.
Sandon bridge gauging station is a barrier to fish.
Runoff from agricultural land and urban to this waterbody having problems with phosphate.
The Sandon Brook gauging station has been assessed and it is confirmed to be a barrier to fish but not eels.
Himalayan Balsam has been most recently recorded on this water body in 2012. 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.
Signal Crayfish have been most recently recorded on this water body in 2012. 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.
Sandon bridge gauging station is a barrier to fish.
Phosphate levels within this waterbody are considered to be too high and therefore have a ‘moderate’ classification. The point source inputs need to be identified although there is a sewage treatment works that discharges into this waterbody.
Himalayan Balsam has been most recently recorded on this water body in 2006. 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.
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.
This waterbody generally has very few issues with the exception being its classification as moderate for phosphate. It is speculated that a local water treatment works may be contributing to this.
This water body has problems with increased phosphate levels. Phosphate is thought to be entering the water from agricultural run-off. This increase in phosphate is causing disruption to the algae and plants within the river.
Turkish Crayfish have been most recently recorded on this water body in 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.
Japanese Knotweed has been most recently recorded on this water body in 2011. This plant not only shades out native plants, but also causes serious damage to buildings.
Himalayan Balsam has been most recently recorded on this water body in 2012. 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.
Floating Pennywort has been most recently recorded on this water body in 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.
American Mink have been most recently recorded on this water body in 2009. 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.
Flood protection structures are present along this waterbody. These may cause a reduction in available habitat and prevent fish migration. The extent of this problem has not been identified.
This water body has problems with increased phosphate levels. Phosphate is thought to be entering the water from a range of different point sources, although many of these have not been identified; one possible input is the local sewage treatment works. Storm discharges are also thought to be having an impact on the phosphate levels. This increase in phosphate is causing disruption to the algae and plants within the river. Along with phosphate, detection of a harmful chemical has been confirmed within this waterbody.
American Mink have been most recently recorded on this water body in 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.
There is no data due to a lack of monitoring within this water body.
Himalayan Balsam has been most recently recorded on this water body in 2012 and 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.
American Mink have been most recently recorded on this water body in 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.
This waterbody is classed as good and there are therefore no significant issues with point source pollution. There is a sewage treatment works present on this waterbody which may have a slight effect by increasing nutrient levels at times.
This waterbody is classified as ‘poor’ for phosphates. Diffuse agricultural pollution could be a reason for this increased phosphate level.
Japanese Knotweed has been most recently recorded on this water body in 2014. This plant not only shades out native plants, but also causes serious damage to buildings.
Signal Crayfish have been most recently recorded on this water body in 2009. 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 a sewage treatment works on this waterbody which could be having an impact on the phosphate levels here.
This waterbody is classified as ‘moderate’ for phosphates. Diffuse agricultural pollution could be a reason for this increased phosphate level.
There is no data due to a lack of monitoring within this waterbody.
There is no data due to a lack of monitoring within this waterbody.
There is no data due to a lack of monitoring within this waterbody.
There is a sewage treatment works on this waterbody which could be having an impact on the phosphate levels here.
Phosphate levels on this water body are classified as moderate. It is likely that diffuse agricultural pollution is contributing to this.
American Mink have been most recently recorded on this water body in 2009. 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.
Phosphate levels on this water body are classified as moderate. This is likely to be because of the discharge from local sewage treatment works.
The non-native invasive Signal Crayfish is found within this waterbody.
There is no data due to a lack of monitoring within this waterbody.
Phosphate levels within this waterbody are considered to be too high and therefore have a ‘poor’ classification; there are also problems with dissolved oxygen levels which are classified as ‘bad’ and ammonia levels which are ‘poor’. The point source inputs need to be identified although there is a sewage treatment works that discharges into this waterbody.
The diffuse agricultural pollution entering the river within this waterbody is described as ‘chronic’. This is the likely cause of the ‘moderate’ classification for invertebrates that this waterbody has.
The non-native invasive Signal Crayfish is found in this water body.
There is no data due to a lack of monitoring within this waterbody.
Phosphate levels within this waterbody are considered to be too high and therefore have a ‘poor’ classification. The point source inputs need to be identified although there is a sewage treatment works that discharges into this waterbody.
The diffuse agricultural pollution entering the river within this waterbody is described as ‘chronic’, there has also been diffuse pollution identified from urban sources.
American Mink have been most recently recorded on this water body in 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.
The invasive Signal Crayfish are present in this waterbody. The Signal Crayfish are likely to be causing problems for invertebrates which have been classified as ‘poor’ in this waterbody.
There is no data due to a lack of monitoring within this waterbody.
Phosphate levels within this waterbody are considered to be too high and therefore have a ‘poor’ classification. The point source inputs need to be identified although there is a sewage treatment works that discharges into this waterbody.
There is no data due to a lack of water testing and investigation within this waterbody.
There is no data due to a lack of biological monitoring within this waterbody.
There is no data due to a lack of monitoring within this waterbody.
There is no data due to a lack of water testing and investigation within this waterbody.
The diffuse agricultural pollution entering the river within this waterbody is described as ‘chronic’.
Signal Crayfish have been most recently recorded on this water body in 2006. 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 no data due to a lack of monitoring within this waterbody.
Phosphate levels within this waterbody are considered to be too high and therefore have a ‘poor’ classification. The point source inputs need to be identified although there is a sewage treatment works that discharges into this waterbody.
The diffuse agricultural pollution entering the river within this waterbody is described as ‘chronic’.
There is no data due to a lack of monitoring within this waterbody.
Phosphate levels within this waterbody are considered to be too high and therefore have a ‘poor’ classification. The point source inputs need to be identified although there is a sewage treatment works that discharges into this waterbody.
This waterbody 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.
Himalayan Balsam has been most recently recorded on this water body in 2012. 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.
American Mink have been most recently recorded on this water body in 2009. 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.
The invasive Signal Crayfish are present in this waterbody. The Signal Crayfish could potentially cause problems for invertebrates in the future.
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.
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The topics below represent the pressures that many waterbodies in the Combined Essex catchment face. They have been divided into six main categories, but it is quite often that these categories can overlap as pressures relate to each other.
Diffuse pollution occurs as water moves across the land or through the ground and picks pollutants. These pollutants can come from a variety of places, including urban and field run off. The pollutants that enter the river can range from sediment to toxins to excess nutrients, meaning that diffuse pollution can cause a whole range of different issues. The variety in these pressure groups means that it is something that can be quite difficult to tackle. It requires groups of people, business and stakeholders to work together in order to solve this problem.
Fish should be able to travel up and down a river freely, allowing them to move and breed in the most suitable habitats for them. It is important that fish populations do not become isolated, as this makes them more susceptible to disease and puts pressure on their survival. Unfortunately, there are often many barriers along rivers that prevent fish from being able to migrate up and down stream. Where barriers have been identified, they will be seen as a ‘pressure’ on a waterbody. Thankfully, there are many solutions now that can be put in place to aid fish passage, even over large barriers.
The flow in a river can vary greatly throughout the year as rainfall and run off can have an effect. This is a natural process. It is when flow is impacted by non-natural processes that it can cause problems. Sometimes, water can be intercepted or removed from a system; this will reduce the flow, therefore changing the habitat conditions. Some species are happy in high energy rivers. This means that when flow is reduced, these species will no longer survive. The opposite of this can occur when excess water is entering a river, for example through increased runoff. Low energy systems then become high energy and displace the species that live there.
A species that is not meant to be found in a particular area is known as an invasive species. Invasive species can be from a different habitat or a different country altogether. Most of the invasive species that we find on our rivers have come from other countries – plants that people have imported for their gardens or animals that have been released for food or by animal rights activists. Control of invasive species requires a lot of time and effort. We are fortunate that we do have a range of methods to manage most of the invasive species that cause havoc on our rivers, but there are still some which we are still struggling to control.
Many of our rivers have been heavily modified over the years as rivers have been used for a wide range of purposes. Physical modification is one of the biggest factors that causes our rivers to be unhealthy. The issues that it can cause range from reducing habitat, preventing migration of mobile species, and even have an effect on the water quality. Where structures and modifications are no longer in use or necessary, they should be removed to allow the river to regain its natural state. Unfortunately, this action is not always taken which means that many of our rivers are over straightened and contain redundant structures. It is possible to return a lot of our rivers to their natural state, through one off projects, but in other cases it is not possible as the river has been changed to protect assets or manage flooding. It is recognised that some modifications cannot be removed without having severe negative impacts both socially and economically.
This is pollution that comes from a single identifiable source. The pollution entering the river could include a whole range of pollutants. Some point source pollution is known about and licences, for example sewage treatment works. Other sources are not licensed, and therefore work needs to be done with landowners to fix the problems that are allowing the pollution to enter the river. Point source pollution is more easily controlled than diffuse pollution as it often only takes one management approach to solve the issue.