Protecting
groundwater
beneath Gardermoen Airport
Jan Erik Kaarø
Senior scientist Sveinung Sægrov at SINTEF NHL believes that Norway's new main airport can be built without changing flow to the groundwater basin under the site.
An impression of the new airport superimposed on the existing landscape at Gardermoen.
Sægrov leads the hydrology groups at SINTEF NHL and NTH's Dept. of hydraulic and environmental engineering, which have been collaborating during the past year with SINTEF Geotechnical Engineering on a study of water balance in the area of the new airport. Their work forms part of the preparations of Oslo Hovedflyplass A/S for its permit application, and of the research program "Faneprosjekt Gardermoen". By integrating simulations made by three different data models, the scientists have created an overall picture of how much rain falls in the area, where it goes and what will have to be done to maintain the water balance. NHL is also creating a basis for the design of the airportΔs future drainage system. The water balance estimates are due to be completed by October 1st.
Environment as important as economics
The researchers have been told by project sponsors Oslo Hovedflylpass A/S that environmental considerations are just as important as economics in the Gardermoen project. The aim is that there should be just as much pure groundwater in the area after 1998 as there is today, and that rivers and surface lakes should not be particularly affected by the development of the airport. Protected areas lie to the south and east of the airport.The SINTEF/NHL hydrologists estimate that 50% of all the rain that falls in the vicinity of the airport ends up sooner or later in the groundwater basin. Sveinung Sægrov believes that this proportion can be maintained without making the airport more expensive than originally estimated.
According to Johan Steffensen, who is responsible for groundwater studies in Oslo Hovedflyplass A/S, the water balance study is an extremely important planning tool, particularly where environmental considerations are concerned.
A distributed waterbalance model
An enormous amount of data lies behind the water balance study. The scientists have collected daily temperature and rainfall measurements from as far back as 1957 to the present day, as well as snow-melt data from 19 seasons. In conjunction with geotechnical data the hydrological measurements were input into different computer models capable of describing the effects of development and of changes in climatic and weather conditions.The scientists from NHL and the Dept. of hydraulic and environmental engineering have built up their own model, known as SINBAD, of surface water at Gardermoen. The model divides the whole of the airport region into a 200 x 200 m grid. The geotechnologists use the American MODFLOW model to simulate groundwater flow, while MOUSE, a Danish model, is used to estimate the correct dimensions of the drainage system. Links between the computer models, and the interdisciplinary collaboration between NHL and Geotechnology, have made it possible to estimate what consequences any type of development will have for the water balance in the region. The study is regarded as an international pioneering project, and it has been presented at two scientific conferences this summer.