6 Future supply
The UK as a whole has more water than it is ever likely to need but much of the water is in the wrong place: areas with the greatest resources are not the areas of highest demand.
Scotland has sufficient water resources for all foreseeable circumstances and has not experienced droughts. An enormous amount of additional water could be made available by reservoir storage in the Highlands. But nowadays there is a trend towards more flexible schemes. In many of these schemes, rivers are regulated by upland reservoirs, and water is abstracted from rivers and lochs in the areas of demand in the lowlands; in others, water supply is developed in conjunction with hydroelectric power generation.
Northern Ireland also has sufficient water resources, most of the supply being provided by surface water sources. Much of the existing storage is in small upland reservoirs, although Lough Neagh, with an area of 385 km2, has become a major source of water for Belfast. Abstraction from Lough Neagh could be greatly increased to meet future increases in demand.
Wales has a considerable amount of water; but much of it is heavily committed to Welsh needs, or to the needs of the north-west and the west Midlands in England. However, there is the potential in Wales for more storage of water if necessary.
England has areas with a surplus of water, such as the north-east, and areas of water deficiency, mainly in the south-east, where part of the supply depends on transfer from other areas. We have seen that in England and Wales the total amount of water abstracted has generally increased since 1993 (Figure 2). To understand how this demand could continue to be met in the future we need to look at the water supplies by region (Table 5). Activity 3 will help you become familiar with these regional differences.
Table 5 Estimated water abstractions in 2001 (public water supply and total abstractions) for EA regions in England and Wales. The values are not the same as in Figure 2, as the values in the table include brackish water.
|EA region||Public water supply /106 m3 per day||Total abstractions /106 m3 per day|
- a.Which region abstracts the greatest total quantity of water, and why?
- b.Which region abstracts the greatest amount of water for public water supply?
- c.Which three regions get the greatest proportion of their public water supply from groundwater, and which region the least?
- a.Wales abstracts the greatest total quantity of water. A lot of this is transferred to other regions.
- b.Thames abstracts the greatest amount of water for public water supply.
- c.The Anglian, Southern and South West regions extract the greatest proportion of groundwater for public supply, and Wales the least.
The rocks of the Wales and North West regions are mainly Cambrian to Carboniferous in age. These old rocks have been compacted, folded and in many cases subjected to metamorphism. They are relatively impermeable and make poor aquifers. The rocks in the Southern and Thames regions are younger — Cretaceous and Tertiary — and are only very gently folded. They are mainly sedimentary rocks, of which the Chalk and sands make good aquifers. The rocks in Scotland and Northern Ireland are mainly older igneous and metamorphic rocks, which make poor aquifers.
The distribution of the principal aquifers in the UK is shown in Figure 10. The three main aquifers are the Cretaceous Chalk (which supplies more than half of the groundwater in England and Wales, as it underlies large areas of south and east England where the demand is high), Permian and Triassic sandstones, and Jurassic limestones. Other aquifers are Carboniferous limestones and sandstones, Permian limestones, Cretaceous sands and Quaternary sands and gravels.
The areas where there are surpluses of water resources over demand in England and Wales for 2001 are shown in Figures 11a, b and c.
Which areas have additional surface water available in winter and which in summer?
Much of England and Wales, except for the south-east, has additional water available in winter. However, in the summer there are few areas with spare water, mainly parts of west Wales and north-east England.
Does groundwater availability follow the same regional pattern of spare surface water?
Not in detail, there is additional groundwater available in small parts of most regions of England and Wales except for the south-west. Although the precipitation is less in the south and east, those areas have major aquifers.
The areas most at risk of future shortages are the Anglian, Thames and Southern regions, areas with low surpluses that depend heavily on groundwater supplies (Table 5). If groundwater is not recharged sufficiently in winter, as happened in the winters of 1995 and 1996 (Figure 8) this may leave insufficient groundwater for extraction during the summer, and may reduce river discharge by a reduction of baseflow.
However, some areas have more water than they need at present. The completion of the Kielder reservoir in the NE region in 1980 doubled the amount of water available to the region, but this water has not been fully used— the demand has risen less than was predicted when it was built and the region now has surplus water (Figures 11a and b). Kielder was built to increase the supply to industry in the north-east, such as British Steel and ICI, who expected big increases in demand. Instead, industrial output has declined and their need for water has fallen since 1980.
Although north-west England (and Scotland) have higher precipitation than the south-east, they have relatively little storage (few aquifers, and reservoirs hold relatively small amounts of water). The precipitation gradient runs one way, the storage gradient the other. So when there is a severe drought over the whole of the UK, the north-west or west often gets into trouble before the south-east. There have not been standpipes or rota cuts in the south-east since 1970, but there have been in Devon and South Wales (1976).
Most of the growth in demand at present, and predicted in the future, is in south and east England. This is a major problem, as these are also the regions of shortage and are vulnerable to drought. Water shortages in these areas are already causing environmental problems such as reductions in river flow and even drying up of some rivers in dry summers. Tackling the river problem would mean reducing abstraction — and increasing shortages.
In 2001 the EA published its strategy for water resources up to 2025 in England and Wales (EA, 2001). The EA stated that its vision was:
Abstraction of water that is environmentally and economically sustainable, providing the right amount for people, agriculture, commerce and industry, and an improved water-related environment.
The EA strategy recognised that:
- in much of England and Wales, water is a scarce resource
- the public water supply provision should be increased by 1.1 × 106 m3 per day
- efficient use of water is essential
- leakage should be reduced.
Agriculture should use available water to the best effect, as in many agricultural areas little further summer water is available. This will involve increased winter storage of water and a change in crops.
As part of the strategy, the EA had to predict future changes in water use and demand. The forecasts were based on the Department of Trade and Industry's 'Foresight' programme, which has scenarios defining a broad framework of possible social, political and technological change. The EA developed four different scenarios, each considering variations in demand by household, leakage, industry and commerce, and irrigation. The effects of climatic change predictions were also taken into account. Scenario alpha, for example, included increasing household demand, weak leakage control and increased irrigation. Scenario delta was for reduced household demand, leakage reduction, low economic growth and lower irrigation use (Figure 12).
The scenarios show that demand for water is highly dependent on societal choice and governance. The general demand for water rises in two of the scenarios, and falls in the other two. Changes are driven by economic pressures, people's desire to see water used in different ways, and technological changes. The EA recommended that the extra water needed for public water supply in scenarios alpha and beta should come from a combination of resource development and demand management; this reflects a change from demand led to demand managed water supply. They proposed resource development of around 1.8 × 106 m3 per day, providing 1.1 × 106 m3 per day for the public water supply (Figure 12) and the rest for environmental improvements. The strategy includes the water companies spending £5.3 billion nationally on environmental projects to improve rivers and coastal waters up to 2005, and £400 million improving water resources related sites, which will protect important wildlife sites. For example, the East Devon Pebblebed Heaths have wetlands which support the rare southern damselfly and other species. South West Water owns two intakes that abstract water from critical parts of the site, which could affect water levels. The company, after discussion with the EA and English Nature, shut down the intakes in 2003.
Most of the EA recommendations for enhancing water resources involve making the most of existing schemes — the inflexible and environmentally destructive days of immediately commissioning new reservoirs seem to be over. The strategy generally recommends:
- increasing winter storage (making use of the wetter winters of climate change predictions), by enlarging existing reservoirs in the south and east, increased conjunctive use in the north-east, and a possible new reservoir in the Thames catchment
- inter-regional transfers, such as the possibility of a Severn-Thames transfer
- utilising rising groundwater in London and Birmingham
- greater re-use of sewage effluent.
Scenarios and strategies have been developed on a regional basis as well as nationally, with targets for regional resource developments and demand management. All regions have identified some resource developments, water savings targets and environmental improvements, but the proportion varies with the situation and need: most of the growth in demand is in the south and east. The Thames region, for example, has a target for resource development of 0.59 × 106 m3 per day, and water savings of 0.75 × 106 m3 per day, whereas the North West region has a target for resource development of 0.035 × 106 m3 per day, and water savings of 0.016 × 106 m3 per day.