23 Rivers Chelmer and Blackwater

In 1927, when the Langford River Treatment works was commissioned, quality control took on a whole new dimension. The former deep wells and boreholes predominantly supplied a pure and wholesome water that only required terminal chlorination as a precaution. The quality of the river supplies however varied enormously, being  easily bacteriologically and chemically polluted, by floods, sewage effluents, industrial and environmental pollution.  This necessitated regular  careful monitoring and appropriate treatment, by professional chemists, biologists and bacteriologists.

River Chelmer

The Rivers Chelmer and Blackwater rise some half a mile apart and approx 34 miles from Beeleigh, where they discharge into the tidal Blackwater Estuary. The Chelmer rises in Rowney Wood, 370 feet above sea level into a small ditch. It is first joined by Stebbing Book, and then at Chelmsford by the River Can into which flows the Roxwell Brook and River Wid. It is  joined by the Sandon Brook, above Lt Baddow, which takes compensation water and overflow from Hanningfield Reservoir. Finally it is joined by the River Ter  at Rushes Lock. Prior to the river being converted to a canal in the 1790’s  it would have been shallower and had gravel stretches as does the River Blackwater now.  As a consequence they would have both supported the spawning of Salmon and Trout, which only the Blackwater does now. 

The River was canalised in 1797, to allow goods to be transported from the Blackwater Estuary to Chelmsford especially timber, by horse drawn wooden barges.  This  increased the volume of the river, the lock gates making the canal section of  similar depth along its length from Chelmsford to Heybridge basin. This acted  more like a reservoir, and also had the positive effect of allowing Chemical and Biological quality improvement.  Leading to a reduction of Nitrate and Calcium  concentration. There was also a negative effect of algal blooms especially in summer, with the lower flows and warmer water. In summer there was an occasional incident when abstraction of water by the water company, reduced the canal level to such that the barges ran aground. Latterly horses were replaced by outboard motors, which had the unfortunate consequence of churning up the prolific weed growth and reducing fish stocks. 

The canal is popular with fishermen and the boating fraternity from narrow boats to canoes. A great friend of mine, and ardent canoeist Mike Robards, likes to shoot the weirs when the canal is in Flood. Some traders in Maldon resisted the plan for the canal to end at Maldon, and so it was diverted to Heybridge Basin instead.  The History of the canal can be found at http://www.chelmercanaltrust.co.uk.

Chelmer Tributary 001


Not Quite on the Chelmer Canal


1777  River Courses from Chapman and Andre’s  map of Essex.   Note the main River Blackwater discharges into the tidal river below Fullbridge

River Blackwater

The River Pant flows for 16 miles from its source to Bocking where it becomes the River Blackwater. It is joined by Robins Brook and Domsey Brook before reaching Witham some  14 miles later where it joins the River Brain. The River Brain initially called Podds Brook flows 14 miles to Witham and a further 4 miles to Beeleigh. It is 380 ft above sea level at its source.  It consistently contained a higher Chloride content indicating  more pollution. Originally the main River Blackwater at Langford, flowed via Langford Mill, then meandered towards Heybridge Mill  discharging into the Tidal River below Fullbridge. A small tributary joined the River Chelmer at Beeleigh. It was most likely that when the canal was built in the 1790’s the main River Blackwater had to be diverted along the path of the tributary. The Mill closed for flour production in 1918 and was utilised by the water Company in 1927 to house water abstraction pumps. The approach to the pump inlets was rebuilt in 1929, with two sluices included to allow water down Langford Cut to adjust the canal level. during times of drought, boats locking at Heybridge basin lowered the canal level. 

In 1952 when the Hanningfield Reservoir Scheme was introduced, a new river Chelmer intake and pumping station were constructed at Langford to supply river water to both Hanningfield Reservoir and the Langford Works, making the intake at Rushes Lock redundant, and necessitating the extension of the sewer pipeline below the new intake to the tidal reach at Beeleigh. Provision was made with an easement (planning Restriction) on land from Beeleigh to Heybridge basin to extend the sewer pipeline further down the tidal river in the event of the District Council wishing to reduce the pollution of the Blackwater at the Hythe Quay and through Promenade Park. This has never been implemented. The pipeline was duplicated in 2015 with a 1.2 metre pipe. An Archeological dig was carried out in advance of the pipeline being laid. Saxon remains from 5000 BC were found including cremated human bones, the earliest in England, together with remains of buildings. The River Chelmer is joined by the River Wid into which flows the effluents of Warley, Ingatestone and Shenfield, and Stebbing Brook into which flows the Stebbing Effluent and that of the Sugar Beet factory at Felstead which at one time imparted an earthy taste and odour to the river



River pollution was always regarded as a threat to water supply, and at the start of war in 1939, the Pure Rivers Society, issued a “Scheme for organised effort to stop river pollution during the war, by encouraging  Anglers to become Voluntary River Watchers. Page 1 of their document shown below.

Pure Rivers Society 1939 pg 1 001 (2)Industrial Pollution

Pollution Incidents on the River Chelmer, apart from sewage effluent incidents, have included

Cyanide solution from an electro plating manufacturing works at Chelmsford, on more than one occasion, killing many fish . In one instance on  the 22nd  November 1948 this was followed by a report of the death of many eels in Heybridge Basin. Their death however was found to be caused by a lack of oxygen and low flow. In the early 1960’s thousands of fish were killed and water was released from Hanningfield Reservoir down Sandon Brook to dilute the pollution.

Also   Tarry Liquor was accidentally discharged from the gas works at Chelmsford

In April 1943 three bombs fell into the River Ter just above the works intake creating a large crater, but  the river flow was not affected

The major sewage effluent discharge from the town of Witham, was like Chelmsford, piped to below the river intakes at Langford. Additionally the smaller sewage works of  Kelvedon, Coggeshall,Silver End, Bocking  and the Cortaulds factory effluent discharge directly into the River Blackwater. The Braintree   Effluent discharging into the River Brain which joins the Blackwater at Witham.

Industrial pollutions have included:-

On the 10th October 1948, hydrogen Cyanide from fumigation of a flour mill two miles above the Intake resulted in the death of a large no of fish.                                        Overflow of fuel oil from the Maltings at Witham                                                                    A Herbicide, 2 3 6 Trichlorobenzoic Acid, affecting Tomato plant growth, was found in the water transferred from the Ely Ouse.

Sewage Effluent reuse   see Page 24  Sewage Effluents

K7 Langford 2015 Enl (2)

Langford Water Treatment Plant with Effluent Recycling Plant on the left

In 1970 when the new water treatment plant was commissioned, permission was granted for a  Dortmund or sedimentation tank, part of the defunct plant, to be used for sewage reclamation trials. Chemical doses of  Activated carbon and a coagulant, Aluminium sulphate were evaluated to achieve an acceptable end product. This work was the continuation of Laboratory scale experimentation, and was described in a paper published by J G Slack in the SWTE Vol 21  in 1972

However no further action was taken until  2003, when a purpose built plant was commissioned using entirely different treatment processes.

Chelmer Ulting Outfall 001

 Scientists David Walker and Sam Vince at Chelmer outfall of Langford Recycling Plant

Blackwater Estuary

The freshwater Rivers Blackwater and Chelmer combine at Beeleigh to enter the tidal Blackwater Estuary, via Beeleigh Weir.  Winding its way through Maldon past Promenade park, it enlarges  into a wide Estuary containing Northey and Osea Islands.  It then reaches Mersea Island where it is joined by the River Colne and later the River Stour. 

It is well known for its Oyster fisheries at Mersea and Maldon, with the Colchester Oyster Feast being a celebrated event marking the opening of the oyster season at the begining of September each year.

It is also a popular haunt of wading birds and as a result of the application to discharge  recycled  sewage effluent to the estuary bird counts were initiated.

Tables shown below give counts at Northey Island and Heybridge Basin, comparing them with National and International counts.Bird Count 1 001

Bird Count Northey Island 001

By courtesy of Essex and Suffolk,  the Recycling Scheme report of 2004