NW's operations are split between two resource zones: Berwick and Fowberry resource zone; and Kielder resource zone.
Berwick and Fowberry This zone covers a small area in north Northumberland, centred on the towns of
Berwick and
Wooler which has no access to stored water and its water supplies come entirely from an
aquifer in the underlying
Fell Sandstone, from which water is abstracted via
boreholes.
Kielder 99% of the population served by Northumbrian Water is in the Kielder zone, so named from
Kielder Water, the largest reservoir in NW's region. The zone is split into three supply zones, Northern, Central and Southern, which correspond broadly to the catchment areas of the rivers
Tyne,
Wear and
Tees respectively, each of which incorporates one of the region's three conurbations. Water is supplied to the treatment works either from a nearby reservoir or by abstraction from one of the major rivers. In the latter case, the flow of the river has to be maintained by discharging water from a reservoir further upstream.
Northern zone The major reservoir in the Northern zone is
Kielder Water. Others include:
Fontburn, on the
River Font, which feeds an adjacent treatment works; and
Catcleugh, on the
River Rede, which is connected by the Rede pipeline with Gunnerton treatment works, 27 miles (44 km) downstream. Catcleugh is also at the start of a sequence that includes reservoirs at
Colt Crag, two at
Hallington and a complex of seven at
Whittle Dene, where there is also a treatment works. Within the Northern zone, water is abstracted from the
North Tyne at
Barrasford and from the Tyne at
Ovingham, with discharges from Kielder Water ensuring that the minimum regulated flow is maintained in the two rivers. From Barrasford, water is pumped to West Hallington reservoir, while water abstracted at Ovingham is used to supply
Horsley treatment works and can also be used to replenish the Whittle Dene complex. The treatment works at Horsley and Whittle Dean jointly meet the needs of Tyneside and south-east Northumberland.
Central zone In the Central zone, the main reservoirs are Derwent and
Burnhope; other, smaller reservoirs are at
Tunstall and
Waskerley, both on Waskerley Beck, and at
Smiddy Shaw and
Hisehope. Derwent reservoir supplies Mosswood treatment works, 2 miles (4 km) away, and Burnhope supplies Wear Valley treatment works at
Wearhead. With the opening of the new Wear Valley works, in 2004, an older facility at Tunstall was closed, and Tunstall reservoir is now used solely to maintain regulated flow on the Wear. The reservoirs at Waskerley, Hisehope and Smiddy Shaw supply Honey Hill treatment works, which lies just below Smiddy Shaw; Honey Hill is also supplied from Burnhope. Water is abstracted from the Wear at
Chester-le-Street to supply a treatment works at
Great Lumley, the minimum flow being maintained through discharges from Burnhope or Tunstall. In the event that neither Burnhope nor Tunstall can satisfy regulatory discharges to meet the minimum maintained flow on the Wear, water can be transferred into the Wear via the Kielder Transfer Scheme, which can also be used to supplement or replace water from Derwent reservoir or to replenish Waskerley reservoir. Coastal parts of the Central zone, including
Sunderland, are supplied with drinking water from boreholes and shafts that abstract groundwater from aquifers in the underlying Magnesian limestone.
Southern zone The largest reservoir in the Southern zone is Cow Green, in upper Teesdale, which is used solely to regulate flow in the River Tees. There are two chains of reservoirs on the
Lune and the
Balder, tributaries of the Tees, which in combination supply a water treatment works at
Lartington, just south of
Cotherstone. The main reservoirs are
Selset and
Grassholme in
Lunedale, and
Balderhead,
Blackton and
Hury in
Baldersdale. Two further reservoirs, at Lockwood Beck and
Scaling Dam, on the
North Yorkshire Moors, are no longer used for water supply and serve purely as recreational facilities. Water is abstracted from the Tees for treatment at the Broken Scar treatment works, near
Low Coniscliffe on the outskirts of
Darlington, and for industrial water at
Blackwell, just downstream from Broken Scar, and
Low Worsall, near
Kirklevington.
Tees Cottage Pumping Station is sited across the
A67 from Broken Scar. This
Victorian facility, which closed in 1980, is still owned by Northumbrian Water, but is now opened as a museum by a Preservation Trust. It contains a 1904-built
rotative beam engine, and a 1914 gas engine, believed to be the largest working preserved example in Europe. ==Kielder Transfer Scheme==