Britpave: The British In-Situ Concrete Paving Association

Slipform paving offers water solution for parched south east

With seven UK water authorities already announcing hosepipe bans, the need for a national water grid to transfer water is again being examined. Concrete slipform technology could provide the solution or is a hosepipe ban the best that we can do? asks David Jones, director of the infrastructure group Britpave.

Parts of the UK have suffered from their driest 10 months since 1888. Some reservoirs such as Bewl Water in Kent are only 40 per cent full. By contrast, the reservoirs in Wales are 98 per cent full. This has led to calls for a national water grid that can transfer water from the wetter North of England, Scotland and Wales to the drier Midlands, South and East.

The transfer of water is not a new idea. The Romans did it using aqueducts and the Victorians built reservoirs in Wales and tunnels to serve the cities of Liverpool and Birmingham. It is an idea that is re-examined every time a drought is threatened and then forgotten once it rains again. However, changing weather patterns due to climate change and the thirsty demands of a growing population, particularly in the dry south east, means that serious consideration should be given to the development of a national water grid. Within 20 years, demand during droughts in the south east will exceed supply by over 60 million litres per day. To help with water supply, Thames Water recently opened a £250 million desalination plant to remove salt from the Tames tidal water and although its plans for a massive £1 billion reservoir near Abingdon were refused by the government, the company still wants to build a smaller one in Oxfordshire while a large reservoir is being planned for Kent.

A few years ago a study by the Institute of Civil Engineers concluded that the provision of a national water grid is both feasible and cheaper than building new reservoirs in the south. The favoured option is to transfer water from Wales using the River Severn to the Thames via a linking pipeline or aqueduct. This is one option that is currently being studied by the Environment Agency which is examining the cost of national water network and plans to report on its findings in the near future.

One option that the Agency should be considering is the use of canals and concrete slipform technology to provide, if not a national, then certainly a regional network for water transfer. Britain already has a system of canals that could be used as the basis for such a network. Concrete slipforming could be used to not only build new canals but could cost-effectively be used to line existing canals to limit water seepage which can be 30 to 50 per cent of the water carried. The concrete slipform provides a lining that is tough, durable and hydraulically efficient. The lining is suitable for both high and low velocities and offers long-term performance with minimum maintenance.

This technology is being used in many countries where there is limited water supply such as the All-American Canal in Arizona, USA, which links the Colorado River to nine cities and 500,000 ha of agricultural land. Originally constructed in the 1930s and 1940s, the 132km canal is unlined and substantial amounts of water are lost due to seepage. To limit this, a new concrete-lined section is being built parallel to the existing canal using a canal slipform paver. In Turkey, a 63km canal section is currently under construction. This is the final section of a 221km canal between the cities of Mardin and Ceylanpinar carrying water from the Ataturk Reservoir into Eastern Turkey. Whilst in the Gujarat region of India, the new Limbi Branch Canal currently under construction will benefit 198 villages.

It is strange that water companies in Britain which has some of the wettest areas in Europe should be announcing a drought before the summer has even started. We have a modern and proven engineered solution in concrete slipforming but unfortunately do not have the vision of the Romans or Victorians to invest in the long-term solution of a national water grid. Is a hosepipe ban the best that we can do?