From canal to tap…
NO LONGER an artery for the transshipment of goods, the Louth Canal now plays a vital role in the supply of fresh drinking water to communities between the Humber and the Wash.
Around 600 litres per second is abstracted by open water transfer from the canalised River Lud to the water treatment works at Covenham Reservoir which has an 11 million cubic metre capacity.
Members of the Lincolnshire branch of the Inland Waterways Association and the Louth Navigation Trust were hosted by Anglian Water Operations for a recent visit along with representatives from the Environment Agency and Mott MacDonald, which is leading the concept design project for the proposed South Lincolnshire Reservoir.
Starting at the intake where the canal water enters a feeder channel to the reservoir, senior operator Jon Battersby explained that it is constantly monitored for levels of agrochemicals such as metaldehyde, which has now been banned, nitrates and phosphates.
This also involves scientists visiting farms to check what is entering the watercourse and to ensure that livestock are prevented from entering it.
In summer when reservoir levels are falling, supplies are topped up from the Great Eau river via Alvingham Lock.
Bar screens provide the first line of defence against debris such as branches, weeds, plastics and even dead sheep. An automatically operated rake clears the screens at preset intervals.
We then walked back along the 400m channel to see the band screens in action. These are continuously rotating drums which fine screen the water. Fish and eels are turned back to the canal.
The water is then pumped into the reservoir through the bank, more during the night although with the introduction of solar panels this will be reversed.
Covering some 200 acres, the reservoir is surrounded by a concrete baffle wall and has a 2.25-mile perimeter. When full, it is 16m deep – Jon commented that he had never seen it lower than 9m.
A watersports facility is leased out by Anglian Water and the reservoir is also used for training by the emergency services and armed forces. The path around the reservoir is open to the public and is popular with walkers but swimming is strictly forbidden.
Raw water storage is a ‘first line of defence’ against waterborne diseases and a ‘jetting’ system induces an anticlockwise flow of water around the reservoir to ensure adequate mixing of water mass.
Gravity-fed into the treatment works, the water then passes through inline strainers which remove fish and eels as well as shellfish such as zebra mussels. Jon showed us a skip full of mussel waste which goes to landfill, as a recycling opportunity has yet to be found.
In answer to a question on invasive species he said that crayfish do not present as much of a problem here as in other places. Zooplankton, algae and other microscopic particles are removed by microstrainers before the water goes through the chlorination process.
Drinking water is then supplied to more than 100,000 properties including Louth, along the coast from Grimsby to Skegness and via Miningsby to the Boston area.
Visitors were also shown the treatment process and had the opportunity to walk underneath the reservoir.