Heatwave puts water in shade

The fight against climate change has heightened concern about floods and drought. But, writes Jennifer Rankin, some of the steps taken to combat global warming might harm water quality and supply.

The long hot summer of 2003 smashed many meteorological records. It was one of the most searing droughts that the European continent experienced, affecting 100 million people and causing the deaths of 20,000.

That summer was a jolt to Europe's politicians and offered a taste of how climate change will affect Europe's water supply. The future will be more testing. Although the risks in Europe are less threatening than in other parts of the world, the impact of climate change on water supply could still be dramatic. By the 2070s, a swathe of southern Europe faces a decrease in the availability of water of around 30-50% according to the European Commission. Similarly the number of rivers 'under stress' is likely to increase from 19% (2007 figures) to 34-36% in the 2070s, with central and eastern European countries hit hardest.

The flipside of climate change is flooding. Here, costs are also escalating. Annual losses from floods in Europe are around Û6.5-Û8 billion. The Association of British Insurers estimates that these losses could increase by a further Û100-Û120bn as a result of climate change, falling heavily on northern Europe.

These days climate change is everyone's top priority. But some green groups are worried that Europe's politicians have not fully got to grips with the difficult trade-offs of environmental policy.

Pieter de Pous, a water policy officer at the European Environmental Bureau is concerned that the focus on carbon dioxide emissions is overshadowing other important issues. He says that policymakers have yet to realise that protecting the environment consists of more than reducing greenhouse gas emissions. Others worry that some countries might use climate change as an excuse for soft-pedalling on commitments in other areas. Beate Werner, head of water and agriculture at the European Environment Agency, says that climate change will be "an additional threat" to meeting the ecological goals of the water quality directive, a flagship EU law on water management (see Page 27).

"Climate change isn't in any way an excuse for not achieving the water framework directive," she says, arguing that countries need to ensure their plans to achieve the directive's goals are climate-change proof.

But perhaps most worrying for the environmental campaigners is that some policies designed to reduce climate change could have unintended consequences, and might even harm water, soil and biodiversity.

At the moment, biofuels are regarded as the biggest potential wolf in green clothing. Werner says that she finds the impact of biofuels on water supplies "concerning" and argues that the scope of debate on biofuels needs to be broadened to consider risks to water and biodiversity. In the US, some scientists argue that the biofuel boom (fuelled by cheap corn) may have contributed to diminishing water quality. Soil erosion caused by planting corn has led to 1.5bn tonnes of pesticide-laden soil being washed into rivers. But the biggest problems for water supply could be in developing economies. According to the International Water Management Institute, a big increase in global use of biofuels could exacerbate water scarcity in India and China. The researchers say that in Europe, where rain-fed rapeseed is used for crops, the amount of irrigation is negligible.

It is not just biofuels that pose a risk. Hydropower can also have negative effects on the environment. Recently Swiss researchers looked at the environmental impact of hydropower plants in a study on the Rhone river. Where stretches of the river had been deepened and widened, the scientists found fewer fish. This was a familiar finding, backed up by previous work. But this study added a new level of detail about the impact of hydropower plants. It found that hydropower plants that use water stored in reservoirs have the effect of reversing natural conditions in rivers. The plants affect water flow, silt levels and temperatures. The river was warmer in the winter and cooler in the summer. All these changes had adverse effects on fish and other marine life.

Climate change is a clear and visible problem on the horizon for Europe's water supplies. But Europe's policymakers will have to tread carefully to ensure the solutions to tackling climate change do not undermine other desirable goals.

The fight against climate change has heightened concern about floods and drought. But, writes Jennifer Rankin, some of the steps taken to combat global warming might harm water quality and supply.