The Johannesburg Earth Summit put resources and sustainability top of the international agenda. With clean water one of the major issues raised at the summit, we ask: Is building large water and sewerage infrastructure the best way of dealing with the world's water shortages?
Chris Binnie, independent water consultant
To answer this question we need to look at the world's water needs in the future in terms of quality, quantity and location and to consider the relevant economic and social factors.
In rural areas the development of small local sources is generally more economic and more appropriate. However, in developed countries the requirements of ever tighter drinking water quality standards have meant ever more complicated and expensive water treatment works requiring greater operational skills.
It is often not economic to build or upgrade small water treatment works. For instance in UK, implementing the European Drinking Water Directive and the cryptosporidium regulations, along with the drive for operational efficiency required of the privatised water companies, has resulted in it being uneconomic to continue operation of many small local sources. Water supply is increasingly based on large water treatment works and associated infrastructure.
In the developing world, population growth continues and water demand is growing fast. In general the land and water resources of many rural areas are unable to support much increase in population and many people are having to move to urban areas.
The result is an appreciable increase in urban population and the growth of many megacities over 10M people. This results in an even bigger increase in demand for water, both for the increasing population and also as economic prosperity leads to higher usage. In many cities more could, and should, be done to reduce demand growth by reducing leakage. However, as we are seeing even in England, with its much slower demand growth, this only postpones by a few years yet higher demand.
For urban areas many local water sources are becoming either over abstracted, particularly groundwater sources, or too polluted, to provide a source of potable water. Thus only large water supply systems can hope to meet the rapidly increasing demands of the burgeoning population of the urban areas and, in particular, the megacities of the future.
Ravi Narayanan, director, Water Aid
WaterAid is the UK's only major charity which is dedicated exclusively to providing safe water, effective sanitation and hygiene promotion to the world's poorest people. In 21 years WaterAid has helped nearly 7M people gain access to life's most basic needs - water and sanitation.
Developing countries have huge variations in development, income, technical capability and availability of freshwater so one solution cannot be applicable for all cases. Three questions could be asked in determining appropriate systems for each situation.
The first concerns the level of service in terms of quality and quantity necessary and the ability of existing freshwater sources to meet these requirements. We normally expect a bore well with a handpump to supply 20-30litres per person per day: compared to the up to 300litres daily used by someone living in a developed country.
The second question concerns the proximity of communities to water sources. Large scale water infrastructure projects may be suitable where access to freshwater sources is assured and where the density of customers able to pay can support a large scale (and therefore expensive) water project.
In rural areas with scattered populations, the financial feasibility of large scale water infrastructure projects is more questionable. In WaterAid's experience, even using the most appropriate low cost technology, the cost of supplying safe water can range from £5 per person in densely populated regions to over £20 per person in more remote, sparsely populated regions. This differential is likely to rise if conventional large scale schemes are considered.
The third question is affordability. The most significant proportion of people without access to safe water and sanitation live in countries with a per capita GDP of less than $500 (£312) per year and daily income of less than $2 (£1.25). If cost recovery is applied to each situation, one has to ask whether large-scale water infrastructure projects can be paid for and maintained by the governments and communities in these countries.
The most important principle in determining the type and scale of water supply projects is to ensure that countries and communities use levels of technology and service that cover the largest number of unserved people, a case of some for more, not more for some.
The facts lEarlier this month politicians at the Earth Summit in Johannesburg voted to halve to 1.2bn the number of people without access to clean water and sanitation by 2020.
lThe World Bank estimates that annual global spending on water infrastructure will have to rise from £53.3bn to £120bn over the next 25 years if targets are to be met.
l78% of engineers polled by NCE said that building major infrastructure projects like dams in developing countries was often inappropriate.
lAid agencies fear privately funded water infrastructure can be inappropriate for poor countries as those building and operating it want to charge consumers for clean water.
lThe ICE has urged the government to take a tougher line on the environmental impact of dams in the developing world when considering whether to help finance them.