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Colne

Colne | Essex Rivers Hub

The Colne Operational Catchment

There are 16 waterbodies in this opperational catchment including the River Colne, Stambourne Brook, Toppesfield Brook, Pebmarsh Brook and Salary Brook. The Colne has been split into 3 sections and covers a total length of 50km. Stambourne (6km in length) and Toppesfield Brook (6km in length) flow into the middle section of the Colne (identified as Great Yeldham to Doe’s Corner), Pebmarsh (5km in length) and Salary Brook (15km in length) flow into the downstream section (identified as downstream of Doe’s Corner). Bourne Brook also flows into the River Colne.

The River Colne rises near Steeple Bumpstead and flows south east through Halstead & the Colne Valley to Colchester, where it becomes tidal before joining the Blackwater Estuary and ultimately the North Sea. The headwaters of the catchment are predominantly rural in nature, giving way to a more urban environment downstream at Colchester. There are a number of abstractions along the river for irrigation and water is abstracted and pumped to Abberton Reservoir for public drinking water supply.

The Colne Estuary is a 2915 hectare National Nature Reserve and designated Special Protection Area (SPA), as well as a biological and geographical Site of Special Scientific Interest (SSSI) and a Ramsar wetland site of international importance. It is a short, branching estuary with five tidal arms flowing into the main river channel. The site includes an intertidal zone of mudflat communities. The estuary is of international importance for wintering Brent geese and Black-tailed Godwit and of national importance for breeding little terns and five other species of wintering waders and wildfowl. Various habitats include mudflats, saltmarsh, grazing marsh, reedbeds, sand and shingle spits, and unused gravel pits. The site supports outstanding assemblages of invertebrates and plants, several of which are nationally scarce.

Colne Gallery

Pressures

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.

Diffuse Pollution

Phosphate levels within the brook are high and for this reason it’s classified as poor.
Dissolved oxygen is also classified as poor with oxygen levels at their lowest in late summer/early autumn. This is due to high temperatures, lower flows and increased aquatic plant growth.
Likely sources of phosphate pollution are agricultural run off.

Flow

Flows are not an issue within the water body but seasonal variations can have an impact on dissolved oxygen.

Point Source

Phosphate levels within the brook are high and for this reason is classified as poor. Dissolved oxygen is also classified as poor with oxygen levels at their lowest in late summer/early autumn. This is due to high temperatures, lower flows and increased aquatic plant growth. The most likely source of phosphate pollution are sewage treatment works and sewage discharges from private houses.

Diffuse Pollution

Phosphate levels are classified as moderate within this water body so some improvement is needed. The main cause for diffuse pollution is agricultural input.

Fish Passage

Barriers are impacting fish levels resulting in a classification of moderate for this water body.

Point Source

Dissolved oxygen levels are classified as bad and they are at their lowest in late summer and early autumn. There are many factors causing this but one factor is point source pollution from sewage discharges. Phosphate is classified as moderate in this water body and there are both point and diffuse pollution sources causing this. The point sources are sewage treatment works.

Diffuse Pollution

Bourne Brook is classified as poor for phosphates. Extensive sampling has shown that the majority of the length of the river is suffering from increased phosphate levels, indicating that phosphate loading is sustained across the whole water body. Therefore it is likely that diffuse agricultural pollution is contributing to this phosphate loading. Higher phosphate levels are likely to be the cause of this water body failing for invertebrates.

Invasive Species

Floating Pennywort has been most recently recorded on this water body in 2009. 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.

Signal Crayfish have been most recently recorded on this water body in 2007 and 2014. 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.
Physical modification
Bourne Brook is modified, with evidence of channel modification at Letche’s Farm, Bourne Brook Bridge, Gosfield Bridge, Gosfield Lake, Slotslough Bridge and Hedingham Road. The effect of this modification has not yet been determined.

Point Source

Bourne Brook is classified as poor for phosphates. Extensive sampling has shown that the majority of the length of the river is suffering from increased phosphate levels, indicating that phosphate loading is sustained across the whole water body. One of the larger sources of phosphate input is likely to be the local sewage treatment works. It is also suspected that there is intermittent point source discharge from other sectors. Higher phosphate levels are likely to be the cause of this water body failing for invertebrates.

Diffuse Pollution

Phosphate levels are high in this waterbody giving it a classification of bad. The most likely diffuse causes are agricultural and urban land management.

Flow

Flow levels are seasonal and are at their lowest in late summer/early autumn. At this time there may be a negative impact on dissolved oxygen levels.

Point Source

Phosphate levels are high in this waterbody giving it a classification of bad. The most likely point source causes are sewage treatment works, misconnections and sewage discharges from private housing.

Diffuse Pollution

Dissolved oxygen levels can be low in this water course, resulting in a classification of bad. The levels are particularly affected in late summer and early autumn due to a number of factors including higher sewage concentrations. Phosphate is classified as moderate in this water body, the exact cause has not been determined at this time.

Flow

Flows are impacted in this water body and only have a classification of moderate. Flow is most affected in late summer/early morning when they are at their lowest.

Physical Modification

Classified as heavily modified for flood protection.

Point Source

Dissolved oxygen levels can be low within this water body resulting in a classification of bad. The levels are particularly affected in late summer and early autumn due to a number of factors including higher sewage concentrations. Phosphate is classified as moderate in this water body, the exact cause has not been determined at this time.

Diffuse Pollution

Phosphate levels are high leading to a classification of poor.

Fish Passage

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

Flow

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 a negative impact at these times.

Invasive Species

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.

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.

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.

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.

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.

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.

Physical Modification

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

Point Source

Phosphate levels are high leading to a classification of poor.

Invasive Species

Signal Crayfish have been most recently recorded on this water body in 2003 and 2007. 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.
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.
There is currently no data but it is very likely that there will be some non native invasive species present in this brook.

Diffuse Pollution

Phosphate levels within the water body are high resulting in a classification of poor.

Fish Passage

The tidal sluice is not impacting passage but more recent dam boards are a possible impact. There is also a culvert under the A120 that is likely to be acting as a barrier to fish passage due to its design. Fish populations are classified as poor and restrictions to migration are having an impact. In addition sediment (local issue) and sewage discharges are also causing fish populations to remain low.

Flow

Flows are low and also impacted by seasonal patterns.

Invasive Species

Japanese Knotweed has been most recently recorded on this water body in 2008. This plant not only shades out native plants, but also causes serious damage to buildings.

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.

Signal Crayfish have been most recently recorded on this water body in 2014. 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.

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.

Point Source

Phosphate levels within the water body are high leading to a classification of poor. Sources have not yet been determined but sewage discharges (from water industry and private properties) are likely to be having an impact.

Diffuse Pollution

The phosphate levels are classified as moderate within brook and dissolved oxygen levels are low and are classified as poor. The exact source of these issues is difficult to determine. These factors are having a negative impact on fish and invertebrate numbers.

Fish Passage

Saline incursion as well as other barriers such as weirs, locks, and sluices will be impacting on fish passage.

Flow

Flow is affected by a number of barriers, one of which being the dam boards installed near the coastal area.

Invasive Species

American Mink have been most recently recorded on this water body in 2007 and 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.

Japanese Knotweed has been most recently recorded on this water body in 2008. This plant not only shades out native plants, but also causes serious damage to buildings.

Carp have been introduced in the brackish area where the river flows into the sea.

Physical Modification

This water body is classified as moderate for physical modification and is also considered heavily modified. The main reason being for flood protection.

Point Source

The phosphate levels are classified as moderate within brook and dissolved oxygen levels are low and are classified as poor. The exact source of these issues is difficult to determine. These factors are having a negative impact on fish and invertebrate numbers. Ammonia has also been classified as moderate in the water body.

Diffuse Pollution

Water quality tests have not been carried out here, but diffuse pollution has been identified as something that may be contributing to this waterbody failing for fish.

Flow

This water body has been identified as having low flows; however, the impacts of these low flows have not been identified.

Physical Modification

Over time this water body has been modified to fit in with agricultural practices, this may be having an impact on the failing fish population as habitat is reduced and sediment load is increased.

Point Source

There is no data due to a lack of water testing and investigation within this water body.

Diffuse Pollution

There is no data due to a lack of water testing and investigation within this water body.

Fish Passage

There is no data due to a lack of biological monitoring within this water body.

Flow

The flow on this waterbody has been classed as moderate. The reason for this classification is due to groundwater abstraction that takes place within this waterbody.

Invasive Species

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.

Point Source

There is no data due to a lack of water testing and investigation within this water body.

Diffuse Pollution

Phosphate levels are high in this water body resulting in a classification of bad for phosphate. There are many causes but the impact from agricultural runoff in the upper reaches is one of the causes for the high levels. Dissolved oxygen levels fluctuate and although there is no WFD failure for this, levels do drop in late summer and early autumn. One of the reasons for this is most likely the increased plant growth, which is exacerbated by the increased nutrient levels in the water from phosphate.

Fish Passage

Fish populations are not as high as would be desired. One cause could be restricted fish passage caused by mill structures along this brook.

Flow

This water body has seasonal low flows, which can have an impact on dissolved oxygen levels in the local area.

Invasive Species

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.

Physical Modification

Fish populations are not as high as would be desired. One cause could be restricted fish passage caused by mill structures along this brook.

Point Source

Phosphate levels are high in this water body resulting in a classification of bad for phosphate. There are many causes but point source causes are sewage discharges from sewage treatment works, businesses and private houses. Dissolved oxygen levels fluctuate and although there is no WFD failure for this, levels do drop in late summer and early autumn. One of the reasons for this is like the increased plant growth, which is exacerbated by the increased nutrient levels in the water from phosphate.

Diffuse Pollution

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.

Invasive Species

American Mink have been most recently recorded on this water body in 2013. 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.

Himalayan Balsam has been most recently recorded on this water body since 2011 in an extensive area. 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 since 2012. This plant not only shades out native plants, but also causes serious damage to buildings.

Physical Modification

Flood protection structures and sediment management techniques are having a negative impact on the ecology of this water body. In particular, although eel populations seem to be increasing, fish populations are suffering.

Point Source

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.

Diffuse Pollution

This water body is classed as bad for both phosphate and dissolved oxygen, with ammonia being classified as poor. Diffuse agricultural pollution is contributing to this although specific areas have not been identified.

Flow

Flow is impacted at this site because of surface water abstraction from Abberton Reservoir. The low flow in this water body is also contributing to failing fish populations. Low flows are causing increased sedimentation.

Invasive Species

New Zealand Pigmy Weed has been most recently recorded on this water body in 2009. This plant forms dense mats in waterways, increasing the likelihood of flooding and also out-competing native species.

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.

American Mink have been most recently recorded on this water body in 2007 and 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.

Signal Crayfish have been most recently recorded on this water body since 2000 to 2008. 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.

Physical Modification

Abberton Reservoir is an unnatural impoundment of water which affects the ecology of this water body.

Point Source

This water body is classed as bad for both phosphate and dissolved oxygen, with ammonia being classified as poor. There is a sewage treatment works that discharges within this water body which could be a likely source of ammonia and phosphates, contributing to the decrease in dissolved oxygen. Other sources could be from local industry.

Completed Projects

Pressures

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.