Water company abstractions are main cause of low flow rivers

Excessive abstractions by water companies are the major cause of the 40 worst low flow problems in rivers in England and Wales, according to a report by the National Rivers Authority (NRA).1 Solutions in each case could cost the NRA and water companies millions of pounds, and the NRA is continuing to identify new low flow problems.

The report covers the NRA's progress in tackling its 40 top priority low flow problems since they were formally identified in February 1990. Although low flows have been exacerbated by drought in recent years, the rivers are mainly victims of local shortages caused by over-abstraction.

The NRA has concluded that 27 of the 40 problems are linked to public water supply abstractions. Dominant causes in the other cases are abstractions for agriculture (6), industry (2) and mining (1). The other four rivers have been knocked off the priority list.

Each of the 36 rivers has been given a "severity" score. Those suffering most are affected by water supply abstractions, such as the Darent in Kent and the Misbourne, near Amersham, with severity scores of 99% and 98%. Other rivers badly affected by water supply abstractions include the Ver near St Albans (91%), the Worfe near Nottingham (79%), and Dover Beck near Telford (79%).

The NRA has already implemented solutions on five rivers, and solutions for another five are in the pipeline. The schemes include compensation boreholes, additional releases of water from reservoirs, and agreements with water companies to limit abstraction.

Costs vary widely. A borehole compensation scheme is likely to cost £50-100,000, but more complex projects cost much more. The most expensive scheme so far has been on the Darent, a river which frequently disappears in its lower reaches as a result of borehole abstractions by Thames Water (ENDS Report 209, pp 9-10 ).

A £12 million action plan has now been agreed for the Darent. The scheme will involve Thames Water reducing its abstractions and extending its distribution system to replace Darent supplies. The NRA will construct artificial springs to feed the river, pump in compensation water from chalk pits ten miles away, and construct weirs along the length of the river.

The costs will be shared between the NRA and the company, but all sums paid by the NRA will be charged to its water resources account. The costs will eventually be paid through higher abstraction charges by customers in the region.

The NRA has also agreed a £2.5 million restoration scheme for the Ver with Three Valleys Water Services. Discussions are under way with the company about another two sites. Remediation of low flows in the river Hiz, near Hitchin, will cost £1.7-7.1 million, the report says, while the price of improving flows in the Misbourne, where Thames Water abstractions are also implicated, "could run into millions".

Another major alleviation scheme is needed to restore Redgrave and Lopham Fen, a Site of Special Scientific Interest in Suffolk. The fen is threatened by Suffolk Water Company's borehole abstractions, relocation of which is likely to cost £4.5 million.

Two paper mills on the Wharfe in Yorkshire are the causes of the only two industry-related problems. Both mills, Garnett & Son in Otley, and BS Whiteley in Pool, hold licenses of right dating back to before 1965. At times of low flows the companies take all the water from the river, leaving stretches completely dry. The NRA is negotiating new abstraction licence conditions with the companies.

The search for solutions to low flow problems is constrained by legislation obliging the NRA to pay compensation when it restricts abstractions. The Department of the Environment has been preparing amendments to the compensation regime for inclusion in the Bill to establish the Environment Agency, but this has been dropped from the legislative timetable for 1993/4.

The process of alleviating low flows is unlikely to stop with the 40 rivers identified in the report. Since its publication, the NRA has identified a further 14 sites which are now being investigated. These include seven sites in the south west, including the rivers Yeo, Tavy and Barle, the Malmesbury Avon in Wessex, and the Foss and West Beck in Yorkshire.

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