Lake Mälaren is a regulated lake surrounded by populated areas including Stockholm, industries, ports and farmland, and its only outlet is the Baltic Sea. It is the third largest lake in Sweden and a reservoir of drinking water to more than 2 million people.
Specialist knowledge from WSP
WSP assessed which option of maximum discharge volume of Läke Mälaren that would give the lowest total risk-costs, considering the calculated risks of flooding (in given worst case scenarios, i.e. flood flows resulting from a storm that would happen on average once every 10,000 years, plus a high sea level providing counter-pressure in the drainage basin).
The risk-cost model constructed was a WSP group effort that combined specialist knowledge of environmental economics, risk theory, hydrology, physical planning and climate adaptation schemes.
Main sustainability outcomes
WSP's results were instrumental to the recommendations given to the Water court regarding the renewal of water rights and the plans to renew the discharge channels to Läke Mälaren ("new locks" - up to 3 times of the current capacity, i.e. large investments in infrastructure). WSP was able to confirm to avoid even larger flood damage costs, especially when flooding affects housing and industrial properties.
WSP has subsequently been assigned to do an extended study in 2009 that includes other preventative options as well as an assessment of the value of maintaining the high quality of drinking water/maintaining the lake as the main reservoir of drinking water in the capital region of Sweden.
How did WSP contribute to the sustainability issues?
By including the value of direct damage costs in a total cost analysis, sustainability considerations are accounted for and measured. There are of course many costs that cannot be translated into monetary terms as easily, such as loss of bio diversity and quality of life. But the way WSP integrated environmental damage costs into the analysis mad sustainability one of the core issues instead of a being only a supporting argument.
Clients: City of Stockholm, consultancy firm Structor
Fees: approx. € 30,000
WSP Project Manager: Johanna Farelius, WSP Analysis & Strategy
WSP co-workers: Petter Stenström, WSP Civils, Anna Gustafsson, WSP Environmental and Johan Lundin, WSP Fire & Risk.