Thursday, September 27, 2012

Climate change impact on groundwater and alpine landscape in Switzerland

Prof. Dr Daniel Hunkeler outlines how Groundwater plays a major role for water supply in Switzerland. How does climate change affect different groundwater resources? What are the consequences for water supply?

The glaciers of the European Alpine region are melting and retreating due to climate change posing issues in management of groundwater and the changing alpine landscape. Temperatures are rising more quickly in Switzerland than the global average: by up to 2 °C since 1900 particularly at high elevations, a rate that is roughly three times the global-average 20th century warming.

Related: The World Wildlife Fund summary from the IPCC 4th Assessment report on Climate change impacts in Switzerland

According to Martin Beniston in Impacts of climatic change on water and associated economic activities in the Swiss Alps (abstract):

Regional climate models suggest that by 2100, winters in Switzerland may warm by 3-5 °C and summers by 6-7 °C according to greenhouse-gas emissions scenarios, while precipitation is projected to increase in winter and sharply decrease in summer. The impacts of these levels of climatic change will affect both the natural environment and a number of economic activities. Alpine glaciers may lose between 50% and 90% of their current volume and the average snowline will rise by 150 m for each degree of warming. Hydrological systems will respond in quantity and seasonality to changing precipitation patterns and to the timing of snow-melt in the Alps, with a greater risk of flooding during the spring and droughts in summer and fall. The direct and indirect impacts of a warming climate will affect key economic sectors such as tourism, hydropower, agriculture and the insurance industry that will be confronted to more frequent natural disasters.

Alpine glaciers are losing 2-3% of their surface area and volume each year. At this rate there will be only very few remaining glaciers at high altitude by the end of the 21st century. Their retreat often leads to the formation of new mountain lakes and will impact groundwater reservoirs.

Climate models predict more winter rainfall and hence a higher risk of flooding and a consequent increase in sediment transported. This may have consequences for fish populations.

The Swiss Alps are a biodiversity hotspot for Europe with over 15,000 animal and 13,000 plant species catalogued. Due to the changes in elevation many of these species may be able to cope with a local tenmperature rise of of 1-2°C . But if temperatures increase more than 3°C, up to 90 per cent of species may be facing extinction.

Groundwater supplies 80% of drinking water

Groundwater supplies 80 per cent of the country's drinking water, and as the glaciers retreat the water quality in lakes and rivers is changing. Water Temperatures in rivers and lakes are increasing and also affecting the temperature of groundwater. Looking at historical data, groundwater temperatures rises corelate with air and water temperature rises as the climate has changed.

Increasing groundwater temperatures may see increased microbial activity and reduced oxygen concentrations which may entail adjusting the pump infrastructure for drinking water. The extraordinary summer heatwave of 2003 provided a glimpse for Swiss scientists and the public at large of conditions to expect by the end of this century and to plan for sustainable water management in a warming world.

Much of the groundwater reservoirs have a significant flow rate, so that during dry periods when river flow is reduced, groundwater flow too may also decrease.

The new mountain lakes created by the retreat of glaciers also pose a problem. They are a significant risk of rock or ice avalanches due to the longterm destabilisation of slopes previously supported by glacier. The collapse of glacial tongues can also trigger a surge wave in the lake with disastrous consequences.

But there are also opportunities for stabilising these lakes with an artificial dam for utilising the water for irrigation, generating hydro-power and as a potential drinking resource in a drier climate.

The changing alpine landscape is also throwing up conflicts of interest between developing tourism of the natural environment and water infrastructure.

These are issues of climate adaptation which each country will face to varying degrees as climate change impacts on the world around us.