Article - Issue 8, May 2001
Water for life: supply and demand in the 21st century
Professor Chris Binnie FREng
Supply and demand in the 21st century
We take for granted that we should have continuous access to a clean water supply. Chris Binnie reminds us that it has not always been so and gives insights on some of the issues the water industry must deal with to maintain a reliable supply for the future.
In which country did 60,000 people die of cholera in a single year? No, not in Africa or Asia but in England in 1849. Cholera claimed so many lives because many people used polluted water sources for their drinking water, thus recirculating the cholera bacterium. The Medical Officer of St Pancras said at the time: ‘Our wells are but the receptacle of the washings from our streets, the permeations from our cesspools, and the filterings from our graveyards’.
The problem of polluted water was overcome in most places by constructing reservoirs in upland areas which had no human habitation, and in some instances no animals either. These reservoirs provided clean water flowing under gravity. The resulting health improvements can be seen in the graph in the reduction in deaths from enteric diseases.
The advent of flush toilets in the mid nineteenth century resulted in the construction of overflows from household cesspools into nearby watercourses and hence into the rivers. Lowland rivers themselves became cesspools. During the hot dry summer of 1858 the Thames became devoid of oxygen over a considerable length. The Great Stink was so strong that sheets soaked in disinfectant were hung in the windows of Parliament but even so it was forced to recess. Only then was the farsighted plan of Joseph Bazalgette adopted. His plan called for three collector sewers on each bank of the Thames to collect the sewage and carry it away downstream to Beckton and Crossness so that none could reach Parliament on the next flood tide.
Limitations on finance meant that late in the nineteenth century few houses had a continuous supply of water. One quarter of London houses were supplied from standpipes running one hour per day, three days per week. In 1900 the President of the Institution of Civil Engineers complained: ‘we should insist upon water being placed on such a footing of constant supply that every consumer may obtain the full quantity which he requires at all hours of the day and night’.
Gradually facilities that used water became more widely available. In 1887 Sheffield had 68,000 houses but only 4000 toilets. By 1920 43% of Bradford houses had toilets and by 1930 the figure had risen to 92%. By the end of the nineteenth century most people had access to public baths, often not used more than once a month. The percentage of houses with baths rose from 30% in 1920 to 56% in 1940. It was not until the post-World-War-II rebuilding boom that these facilities became universal and public water supplies and sewers reached most rural areas.
So how do we fare today?
Water-using appliances are now widespread in the home and help with the washing of dishes and clothes. Baths and showers are used several times a day. Recent additions to the list of water-consuming appliances include power showers, beloved by teenage daughters, and power sprays for cars. All these have raised the demand for water in England and Wales from 10,000 Mld (Megalitres per day – one Megalitre equals one million litres) in 1960 to 17,000 Mld in 1995.
The unusual drought of 1995 resulted in widespread shortages of water. Hosepipe bans and Drought Orders were instituted in many parts of the country. Upland reservoirs in Yorkshire almost ran dry. To save water, Yorkshire Water proposed the use of rota cuts and standpipes in the streets. These were vetoed by Government as not providing an acceptable level of service in the 1990s and a massive tankering operation took place instead to maintain full supplies. The water companies were able to maintain supplies to customers – just – by adopting emergency measures and, in some places, laying new pipelines to areas suffering a shortage of water in a fraction of the normal time. There were, however, several places where abstraction affected the environment.
The Government and water companies realised that the demand/supply balance was inadequate and that they should institute demand management measures. In 1995 about 30% of water in the supply system was lost as leakage. Most leakage occurs at night when usage is low and hence water pressure is high.
Since 1995 water companies have set up District Meter Areas so that they can monitor flows at this level and identify areas of higher night flow (which probably indicates leakage as night use is low) and pinpoint places where water flows have increased (again probably a new leak). The companies have developed computer models to identify critical pressure points in the system. They have installed variable-pressure reducing valves which they control to ensure that the minimum pressure is always achieved but seldom exceeded. Specialist teams have been set up which use electronic sounding equipment to locate leaks and then repair them rapidly.
The result is that since 1995 leakage in England has been reduced by nearly 40% to below 20% (see graph above). However, almost all water companies are close to, at, or below their economic level of leakage and the scope for further reduction is limited.
The water companies are now also involved in longer-term water demand management. This involves issuing general pamphlets on the importance of water and education packs for schools, providing cistern displacement devices to reduce the amount of water in each flush, encouraging appliance manufacturers to improve water-use efficiency, reducing the size of new toilet cisterns to 6 litres’ capacity, encouraging use of rainwater butts, demonstrating water-saving gardens, encouraging better design of houses to use less water, and promoting industrial waste minimisation. Most of these measures provide limited benefit, often at a cost higher than the long-run marginal cost of water.
The greatest scope for improvement is in industrial use minimisation. Minor investment or a change of traditional operational practice can save significant amounts of water: payback periods are often below two years and such measures bestow good environmental credentials.
Since 1990 all new houses have been metered. Surveys have shown that, broadly, metering reduces consumption by about 10% and cuts peak summer flows by about 30%. It is now in general financially advantageous for people with small families and larger houses to be metered. By switching to a metered supply I save over £100 a year.
Some parts of the country now have nearly 50% of houses metered; the average for England is about 20%. Metering of domestic customers is expensive for the water companies and almost nowhere is it an economical form of demand management. However, it does send the right message of water conservation and waste minimisation and encourages the use of other demand-management measures.
Water abstraction licensing
All significant water abstraction from rivers or groundwater has to be licensed by the Environment Agency. This procedure was established by the Water Resources Act of 1963. Under the Act any pre-existing abstractor could obtain a licence as of right for the quantity that he considered he had been abstracting and these licences last indefinitely. The Environment Agency now considers that in some places the river environments need greater flow than they can currently have and that this licensing system does not provide the Agency with sufficient management flexibility.
The Environment Agency (EA) now issues all new abstraction licences on a time-limited basis and wishes to convert all existing licences to be time limited. The draft Water Bill includes a provision that the EA could revoke any licence not used for 4 years. Since the water companies have a statutory duty to supply water, they are worried that they could lose access to their raw material. At the same time Government is considering the trading of abstraction licences. The conundrum is: who is voluntarily going to release a licence if, in the future, it could be sold? Trading does occur now. Those with licences they do not use, such as industrial plants, should consider whether to sell them now.
The EA is now beginning to draw up Catchment Abstraction Management Plans. These will identify which water the Agency considers is needed for the environment and which portions of the river flow are already over-licensed. These plans will form part of the River Basin Management Plans required by the new EU Water Framework Directive.
Climate change has been a regular topic in the media in recent years. The prognostication from the Met Office Hadley Centre is that temperature will increase, overall rainfall will change little but in general winter rainfall will go up and summer rainfall down, particularly in the south and east. The increasing temperature will result in increased evaporation and evapo-transpiration. The result is expected to be that summer river flows will reduce, particularly in the south and east. Since, because of the increased temperature, the needs of the environment will be for more water not less, the water available for abstraction from rivers in summer could reduce appreciably.
For groundwater sources the effect of climate change could be that the recharge season will shorten somewhat, due to the higher evapo-transpiration, but the higher winter rainfall will at least compensate for this. The EA believes that the water available from many aquifers is already fully licensed. The Agency is now considering whether part of the aquifers’ ‘yield’ (the maximum amount of water that can be abstracted on a long-term basis), say one third, should be allocated to the environment, thus reducing the amount available for abstraction. This could mean a reduction in the size of abstraction licences.
Future demand/supply balances
The result of all the changes discussed above is that the water resources available to water companies could well reduce. So what effect would this have on the demand/supply balance? At the moment this is difficult to predict: it depends critically on the Agency’s view on environmental needs and this has not yet been established.
There is of course one water source that provides a continuous flow, barely affected by climatic drought: namely, treated sewage effluent. Shortly all towns with population above 2000 will have at least secondary sewage treatment and the processes are now much more successful and reliable. Windhoek in Namibia has used treated sewage effluent for up to 30% of the municipal water supply for the past 30 years without any apparent ill effect, and no public concerns.
Already Oxford’s treated effluent is London’s water source, albeit indirectly via the Thames and some days later, and many other lowland towns are in a similar position. However no UK water company has yet dared to take the step of direct recirculation. As a member of the public what would you think of this idea? Certainly there would need to be care in identifying and eliminating certain chemical discharges to contributing sewers. There was previously some concern over endocrine disrupters, which might affect the potency of men. The treatment process would need to be seen to be robust: the latest extension of the Windhoek plant includes membrane treatment, ozonations, and adsorption on granular activated carbon.
This is now less a technical issue than one of planning control and social acceptability. In the UK implementing such schemes would mean putting greater restrictions on what industries could discharge into the public sewer. For a large water-using industry located near a sewage treatment works, there may be economies in future in obtaining a water supply from there.
Water resource development
If significant new sources of water are required in future then they are unlikely to come from extra groundwater or from extra summer river abstractions. Most water companies have already integrated their resources to maximise the yield from conjunctive use. Water is heavy and viscous so the long-distance pumping of larger quantities is uneconomic. The main solution that remains is to store surplus winter water in reservoirs – a sustainable and renewable source.
There has been much agitation overseas in recent years against dam building. The protests have been caused by the construction of really large dams which have flooded reservoir basins with maybe 100,000 people living in them. The Three Gorges Dam in China is requiring the resettlement of over one million people. In developing countries there is often not the finance, bureaucracy or resettlement land to ensure the fair treatment of those affected. Quite often there is not the political will by a central urban government to look after a rural population who are often of a different tribe or allegiance.
The result of these disturbances has been the recent report of the World Commission on Dams. The report focuses on the involvement and rights of those to be displaced: they should give their prior, informed consent. Most of the procedures being proposed are similar to those already practised in the UK. One aspect of the proposals is that a wider range of options should be taken into consideration: the raising in height of an existing dam has seldom been considered until recently. For a pre-existing dam the social and environmental effects of raising it are often small and since much of the inlet/outlet/spillway infrastructure exists such a change can often be made very cost effectively.
Drinking water quality
The quality of our drinking water has changed greatly since Victorian times. Originally there were no quality standards. The 1935 Public Health Act required suppliers to provide ‘wholesome’ water but what this meant was never defined. In reality ‘wholesome’ came to mean ‘bacteriologically safe’; with the treatment processes of sedimentation, filtration and disinfection, water treatment became largely process driven. As a young water engineer I was told by the Chief Engineer of one rural Water Board: ‘we know we have a lead problem so we never test for it!’
These practices all changed with the introduction of the EU Drinking Water Directive in 1989, which resulted in about £5 billion of investment in new and improved water treatment processes. Now water is sampled at the customer’s tap and many different parameters are tested and compared with the strict values in the Directive. In 1999 some 99.8% of UK tap water passed the tests.
The main remaining problem is lead which can affect young babies, pregnant mothers, and possibly menopausal women. The standard for lead content is being tightened over the next decade. The removal of all lead pipes connecting company mains to customers would be very expensive and highly disruptive whilst the work was being carried out. It would in any case be of little benefit unless householders also replaced their lead pipes, and there is little sign of that happening. The result is that water companies are developing treatment methods which should enable the water quality to meet the new standards.
Capital maintenance of assets
A major concern of the water companies is the amount of money they are allowed by their economic regulator OFWAT to spend on capital maintenance of their assets. The value of the assets is some £140 billion. Companies in general based their funding request for 2000–2005 on current and future asset condition, with the intent of trying to avoid failure of the system. OFWAT rejected this approach and, using serviceability indices based on failure rates but little affected by capital maintenance, claimed that serviceability was largely stable and hence capital maintenance should be stable. This ignored the fact that the asset base is increasing (particularly in shorter-life assets such as IT and control systems) and that nearly £1 billion worth of pipes had moved into the worst-condition categories in the previous five years. OFWAT then applied onerous efficiency factors to reduce funding further.
The result is that replacement rates for water pipes are generally some 150 years and for sewers some 1000 years, way beyond original design lives. For most companies it is not even possible to replace all grade 5 assets, those defined as ‘substantially derelict and source of service problems. No residual life’. The House of Commons Environment Audit Committee accused OFWAT of ‘intellectual neglect’ of capital maintenance. Efforts are being made by the water companies to identify and agree with OFWAT a suitable risk-based methodology for the future.
Flooding from sewage
There are still a small number of households at risk of flooding from sewage. This is a most unpleasant experience and should be eliminated. Unfortunately all the easy cases have been dealt with and those that remain are expensive to put right, in some cases costing as much as the value of the house. The water companies requested significant funding to deal with this issue but OFWAT, in its effort to reduce bills to customers, slashed this programme. Most affected householders will now have to wait at least another five years.
By the end of the Second World War the pollution in our rivers was often awful. For instance in the 1950s the Thames was devoid of oxygen for some 20 miles and immediate stomach pumping was needed for anyone unfortunate enough to fall in. Most coastal towns saved their ratepayers money by releasing largely untreated sewage through outfalls discharging near the low-tide mark.
Since then the Control of Pollution Act, and then EU Directives for Bathing Beaches, Shellfish, and Urban Wastewater, have required massive expenditure on modern sewage treatment works. Now over 80% of our beaches meet the mandatory standards. There are proposals for a new Bathing Water Directive which will raise standards even further. In addition some EU countries believe that the North Sea suffers from algal blooms and should be classified as a ‘sensitive water’ – hence all sewage works discharging into it would need first to remove all nitrates and phosphates from the effluent. The UK government does not consider this proposal is justified and is resisting it.
The EU Water Framework Directive
A major environmental and investment driver will be the new Water Framework Directive. In broad terms it requires waters to become ‘good’ – generally defined as having ‘only slight changes from a water body under undisturbed condition’. The working definitions of ‘good’ will vary from region to region and have not yet been worked out. However, implementation has to be achieved by 2015 and is expected to require the further upgrading and improvement of sewage works at an estimated cost of the order of £10 billion. Industry will, in many cases, have to improve its liquid effluent quality as well.
Finally we have recently seen and experienced many instances of river flooding. There are many fundamental problems to be overcome here. One is an archaic and cumbersome administrative system for flood defence, reporting to MAAF. The major issues are no longer flooding to, or caused by, agricultural land. They are urban development issues which should be the responsibility of the DETR. Funding has been inadequate for decades and needs to be increased appreciably. No longer should developers be allowed to build in a flood plain. If such building is essential then the developer should be required to fund the flood defences. New development, with its impermeable roofs and car parks, naturally increases the speed and amount of runoff and thus increases the risk of flooding downstream. All new developments, including those for industry, should be required to put in water detention systems to overcome this. Many people claimed after last year’s floods that they did not realise they were at risk from flooding. The Environment Agency now has flood risk maps: it should be a requirement for the solicitor of a house buyer to consult these and ascertain if there is any flood risk.
The good news during the recent flooding was that the new Environment Agency flood warning system – using rainfall radar, reporting rain gauges and real-time river-flow models – enabled the Agency to issue appropriate flood warnings in due time. No one drowned from lack of warning. This system is the way ahead but it still needs extending and refining.
In summary our water supply and wastewater disposal systems have developed much since Victorian times. As a result public health has greatly improved, as have social wellbeing and the environment. However today’s achievements will be judged by tomorrow’s standards. There are a number of important issues to deal with ahead, as well as significant investment to be made, in order to achieve the standards of tomorrow.
In 1995 about 30% of water in the supply system was lost as leakage
the water available for abstraction from rivers in summer could reduce appreciably
The main solution that remains is to store surplus winter water in reservoirs – a sustainable and renewable source
All new developments, including those for industry, should be required to put in water detention systems
Professor Chris Binnie FREng
Deputy Chairman, Binnie Black & Veatch
Chris Binnie is Deputy Chairman of Binnie, Black & Veatch, one of the foremost water engineering consultancies in the UK. He was previously head of water consultancy and main board director of WS Atkins plc. He has worked on water supply schemes throughout the UK and in many other parts of the world. Email: Chrisbinnie@email.msn.com