Thames Water told to scrap major reservoir plan

The environment department (DEFRA) has told Thames Water to rewrite its plans to meet the needs of its customers over the next 25 years. The company has not justified its plans to build a new reservoir in Oxfordshire.

There is no need for Thames Water to build a major reservoir at Abingdon, Oxfordshire, the environment department (DEFRA) says.

The comment is made in a decision letter issued on 4 March, following a public inquiry into the company’s long-term water resources plan.

The letter says that Thames’ proposal to build the controversial 100-million cubic metre reservoir would not be efficient or economical.

It must now work with the Environment Agency to draw up a different solution to meet future demand needs, which are much lower than those claimed by Thames. This could still include a reservoir at Abingdon, but half the size of that originally proposed, according to the planning inspector’s report on the inquiry. But Thames should also consider a range of smaller options such as effluent reuse and produce a revised plan in six months.

The decision is embarrassing for Thames as it first announced plans for the reservoir in 1990. It said the scheme was needed to meet projected supply shortages in the Swindon and Oxfordshire areas, and to regulate flows and boost London supplies (ENDS Reports, November 2003 and September 2006).

Thames has maintained this, in spite of the its high leakage rates and low levels of metering. The initial draft of its water resources plan predicted metering rates of just 39% in 2030. It is now saying metering will hit 80% by then.

Thames’ final draft, published in 2008  said the reservoir was needed principally to deal with two long-term risks (ENDS Report, May 2008). Firstly, that the agency will cut the amount of water Thames is allowed to abstract from the river Thames and the Lee. The reductions would ensure the rivers meet the environmental requirements of the EU Water Framework Directive. Secondly, there is a risk Thames may have to provide “major bulk supplies” to other firms.

Thames planned to provide 100 megalitres per day of water above demand forecasts to deal with these issues using the reservoir.

But this assessment was questioned by DEFRA in its initial response to the plan (ENDS Report, August 2009), and by the planning inspector. The inspector’s report points out that the agency has yet to ascertain what reductions will be required, if any, to meet the directive and that Thames has no obligation to supply other firms with water. Furthermore, the water resource management plan is subject to annual review, and revision every five years, so the agency’s work can be taken into account in future plans.

The inspector suggests Thames picked the figure of 100Ml/d simply to justify the reservoir. “[I have] some sympathy with concerns expressed at the inquiry that the [plan] has been produced in order to support the [Abingdon] project,” the inspector writes.

Thames did not properly assess alternatives to the reservoir when drawing up its plan, the inspector adds. “Potentially feasible options... have either not been considered or have been rejected before sufficient evidence has been gathered to justify their exclusion.”

If Abingdon is removed from the plan, Thames has a shortfall in the water it needs to supply from 2025/26. The shortfall will hit 58Ml/d in London in 2035 and 1Ml/d in Oxfordshire. The inspector says the options Thames should consider to meet this include:

  • Transfers from the river Severn
  • A 50 million m3 reservoir at Abingdon
  • Large effluent reuse schemes, such as that being trialled at its Deephams sewage works

It must also take account of potential future reductions in the amount of water it supplies to Essex and Suffolk Water and Veolia Water Central.

Thames Water issued a press release on the decision, which chose to skirt the Abingdon issue. Instead, it pointed out that the inspector recommended no changes to the company’s demand management plans, including its leakage and water efficiency work.

Two other water companies’ plans were not immediately given DEFRA approval in 2009. South East Water was finally given the go-ahead to publish its plan last year following a public inquiry (ENDS Report, December 2010), although there were doubts about the fitness of the plan after 2020. Portsmouth Water is consulting on a revised plan. 

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