Running dry

As the summer of 2005 approaches, things are not looking good for the water reserves of south-east England.

After an exceptionally dry winter, though reservoirs are full, boreholes near London are at only 50 per cent of their capacity and parts of the UK’s driest region are already facing the first hosepipe ban since 1996.

And it is not just Britons who are suffering. Portugal is in the midst of its worst drought for 300 years, while parts of Spain are so dry that councils are refusing to fill swimming pools and have turned off public fountains.

Meanwhile, on the other side of the globe, Sydney is facing its worst drought on record, with dam levels at just 40 per cent of capacity. Police have been seconded to root out people flouting hosepipe restrictions, and fines for those found wasting water can be up to £25,000.

Despite the distance between them, Sydney and London have much in common — at least when it comes to securing their future water resources. The principal suppliers to both cities, Thames Water and Sydney Water, have been holding technical exchanges for the past 15 years.

Both face the problem of a growing population with increased water demands, coupled with an increasingly dry climate caused by global warming.

In both cities the margin between supply and demand is narrow, despite the suppliers’ efforts. In 2004 Sydney Water, the Sydney Catchment Authority and the Department of Infrastructure, Planning and Natural Resources released a Metropolitan Water Plan, under which ways to bridge the supply gap were set out.

However, last month an analysis by  the New South Wales Audit Office said a five per cent drop in rainfall caused by climate change could return the city to a water deficit.

Back at home, another 800,000 residents are expected in London by 2016, boosted in large part by government plans for huge expansion of housing in the Thames Gateway region. This is the equivalent of the population of Leeds arriving in the city.

Not only is London’s population growing, but also increasing ownership of appliances such as dishwashers means water use is rising from around 120 litres per person per day to 150. In the UK, water companies must produce long-term resources plans that look 25 years ahead, taking into account factors including available supply as well as forecasts of the amount of water their customers will need. The plans are then assessed by the Environment Agency, which reports to the government.

The last review took place in 2004. Although plans for the Thames region were deemed adequate, since the report plans for the area have not run smoothly — meaning that London could be left facing a deficit too.

Thames Water aims to meet demand through reducing leakage, developing groundwater use and building a large reverse osmosis desalination plant in the Thames Estuary by the end of 2007. Water taken from the river would be filtered, treated, then forced through a membrane to remove its salt.

However, despite being given planning permission by the local council in Newham, the borough where it was to be built, the facility has since been vetoed by the Greater London Authority. ‘Desalination plants are not seen as sustainable,’ said Jean Venables, vice-president of the Institute of Civil Engineers.

The ICE examine the issue of water supply as part of their State of the Nation yearly audit of the country’s infrastructure. ‘Desalination plants use a lot of energy to obtain fresh water and their long-term feasibility is questionable — which is why the mayor is objecting.’

While Sydney has access to upland areas where reservoirs can be built and where water in them is unlikely to be contaminated by run-off pollution and pesticides from farms, this is not the case in London.

Plans by Thames Water to build a new reservoir in south-west Oxfordshire have met with resistance from planners.

Instead, the utility company Thames has turned to technology. The company is already using the chalk layer under north London as a reservoir, pumping in water during wet periods for later use in the summer, a process known as artificial recharge.

A similar scheme is planned for south London, possibly by 2013. Filtering and processing technologies have also advanced to a stage where ‘grey’ water (waste water from showers, sinks and washing machines) is collected, filtered and chlorinated for re-use as non-drinking water that could be used for almost anything.

‘We can turn waste water into drinking water but people don’t want to drink it,’ said Tony Rachwal, R&D development director at Thames Water.

‘In other countries there have been concerns over using it for washing clothes. We call it the yuck factor.’

Re-use of grey water for certain functions is proving very popular in Sydney, with a little help from legislation. The state government has developed a scheme called BASIX, the Building Sustainability Index. Under this all residential buildings built within New South Wales from this week will be required to reduce their potable water consumption by 40 per cent compared to the average of existing housing stock.

This can be done through collection of rainwater for toilet flushing or connection to a recycled water supply. The city’s Rouse Hill suburb is seen as a pioneer for this scheme. More than 15,000 properties have two water supplies: recycled and drinking water.

The recycled water system is coloured lilac, including the taps, so that the two are not confused. The system, known as dual reticulation, has reduced water demand by 35 per cent per household by using recycled water for gardening, washing cars, toilet flushing and parks. Another 10,000 houses will be added by the end of 2006.

Rachwal admits Sydney is ahead of London in its use of recycled waste water. However, Thames Water has also come up with a new approach to allow its unique desalination scheme to go ahead. ‘We are discussing the use of renewable energy to power this. While countries in the middle east use desalinated seawater, London is pioneering the use of estuary water instead. Sydney has not yet done this, despite having a large harbour.’

The Newham plant also faces the problem of obtaining planning  permission for its associated power generation capacity, with the result that the company will have to come up with an innovative solution.

‘We couldn’t get permission for a large wind farm in the middle of London, for instance,’ said Rachwal. ‘Instead we’re looking at fuel cells, methane or tidal power.’

The company also plans to spend around £500m on replacing ageing mains equipment over the next five years. The aim is to cut water waste from leaks by 20 per cent, or 180 million litres per day — enough to supply the daily needs of over a million people.

However, this is not a straightforward process. ‘A problem with trying to reduce leaks in central London in the fact that it disrupts traffic,’ said Venables, ‘It is also expensive. There is a big problem with the infrastructure, though the company is looking at technologies such as those allowing them to reline pipes without digging up the road.’

To identify leaks before they occur, Thames Water has developed an intelligent ‘pig’, a device created originally for use in the oil industry. It is pushed through pipes to clean or inspect them and uses ultrasound to look for cracks and corrosion.

The first field trials of a small version for use in 200–300mm pipes are taking place, and a large-scale version is planned over the next two to three years if all goes well. Severn Trent and United Utilities are also involved. ‘The oil and gas industry uses electromagnetic inspection for its steel pipes, but this doesn’t work as well in the iron piping we encounter,’ said Rachwal.

‘Electromagnetic devices need to be within a few millimetres of the pipe wall, but if we used this we could damage piping by knocking off rusty deposits and this would contaminate drinking water.’

Instead, the new device is neutrally buoyant and floats in the middle of the pipe.

Another system under development is a network of wireless sensors embedded in sewer manhole covers. Though their initial use will be monitoring water capacity within  drains to allow heavy localised rainfall to be redirected and avoid floods, eventually the system could be adapted to transfer rainwater to processing plants for treatment and underground storage.

The government’s house-building plans will create problems that will add to that of their owners’ water demands. When large areas are covered in asphalt and concrete, such as in big retail parks or suburbs where gardens may be paved to create car parking, any rain is likely to run straight into drains and away to rivers without having the opportunity to soak into the ground. This also creates the ideal conditions for a flood, should the rain be heavy enough.

Unfortunately, according to the Environment Agency, climate change is bringing conditions where more rain falls in winter compared to summer. This rain tends to arrive as large downpours rather than a steady stream, leaving the region increasingly seesawing between flood and drought as the seasons progress.

‘The Thames Gateway is technically a semi-arid area, if you look at it in terms of water supply and demand,’ said Venables.

‘However, the current planning system doesn’t allow water supply to be a factor for limiting house building.’

According to the ICE, various measures are needed to ensure that new-build houses and facilities are water efficient. ‘We need to capture water in the uplands of the Thames and use it to replenish the groundwater lower down, ready for extraction in the summer,’ said Venables.

The increasingly common intense downpours are less useful in replenishing aquifers as water tends to run straight off to sewers.

‘We need to think about how to get the storm water to stick around,’ she added. One possible solution to this lies with the firm Tarmac, which has recently launched a surfacing material that will enable rain to be stored, rather than allowing it to run off into the ground or straight to the river.

The material, known as Aquifa, consists of two or three asphalt layers over a porous granular layer that can accommodate up to 30 per cent of its volume in water. ‘As an example, if a road is 45cm deep, 15cm of that can contain water,’ said Dr Howard Robinson, head of product development at the Tarmac Group in Wolverhampton.

‘The Transport Research Laboratory has tested it and has confirmed that it can perform as well as a normal road.’ As Aquifa has a porous surface, this puts it in danger of being more easily damaged than a normal road, however. So Tarmac developed a strong reinforced bitumen to layer over the surface to protect it.

Aquifa has so far  been used at the Pompey Centre retail park in Portsmouth and on newly-built private drives in Bristol. ‘The main use will be for hard shoulders, car parks and cul de sacs,’ said Dr Robinson.

‘It is almost as fast to build as a normal asphalt road.’

Once the water has been stored it will either soak slowly into the ground below or, if an impervious membrane is laid below the porous layer, it can be drained to a holding tank and recycled as grey water. ‘New-build housing could have a drive and the area around it made from this, then the water could be used for flushing toilets, which accounts for around a third of domestic water use,’ said Robinson. H

owever, he admits that generating interest in the product has been hard, despite its benefits. ‘It was a bit of a struggle getting access to the Thames Gateway team but they are looking at it. However, the construction sector is very conservative and it takes time to get a new product in.’

Though these technologies look promising, ultimately their fate is in the hands of the consumer. ‘All these systems depend on whether they work, are reliable and whether we can afford it,’ said Rachwal. ‘At the end of the day people aren’t prepared for huge bills. We have to supply water, but at a manageable cost.’