Wednesday, 6 February 2013

Dams: a double-edged sword?

Are dams enhancing or crippling our financial and environmental balance?

Dams have long been relied upon as defences against flooding, supplying renewable and low-carbon energy (hydroelectricity) and water storage, but recently, questions have been raised over their sustainability. The high pricing of the  structures has been widely acknowledged and accepted; previously, benefit-cost analysis resulted in worldwide dam systems being readily installed. With climate change and rising sea levels at the forefront of many government agendas, dams proved a sustainable approach to mitigate the existing global warming impacts of excessive flooding. For example, the controversial £1.85 billion dam in Patagonia, Chile was built despite the landmark’s potential threat to wild deer species and Laguna San Rafael National Park.

Puclaro reservoir, northern Chile

However, researchers in Chile have questioned how effective dams are in defending against floods, as they are known to increase rainfall intensity – a phenomenon known as the “lake effect”. Large water storage bodies increase rainfall in their surroundings by a significant amount. More water is available for evaporation, and ultimately precipitation; one study highlighted a 4% increase in rainfall each year since dam construction. The proposed lake effect holds the potential to breach existing flood defences downstream as sea levels rise in concentrated areas. Engineers are often criticised for their designs as flooding continues following dam emplacement, although this could be beyond our control, as nature dictates the hydrological processes occurring in these reservoirs.
The extent of these detrimental environmental impacts proves an inconvenient truth for many due to the high expenditure of redesigning such structures; despite hesitations about dam-induced flooding, Professor Richard Harding from the UK Centre for Ecology and Hydrology (CEH) declares “The physics [of dams] says that it will happen”.
(Source: BBC)

By Ellen Kane, Action 21 volunteer