Digital tools help ensure groundwater quality
A sum of DKK 20 million annually in 2012 and 2013 have been used to increase our knowledge about the risks related to groundwater boreholes. Ramboll has developed a digital tool to help municipalities address this problem.
The optimal protection of groundwater resources is of crucial importance and will be in the future. Thus, the Danish parliament has earmarked DKK 20 million in 2012 and 2013 to protect the groundwater from threat of pollution that can occur in boreholes in connection with wells.
The money will be used to identify and document the so-called sanitary protection zones of water intakes (BNBO), where the threat from pesticides and fertilizer is especially serious.
When the groundwater is pumped up from the boreholes, a kind of depression cone in the groundwater is formed around the borehole. Within the area of this cone, there is a greater risk of pollution from surface area that can trickle down into the groundwater.
Because of the specific soil conditions, the depression cone is not always circular. Therefore it is important to map the area of the depression cone for every specific borehole, the so-called BNBO.
Selecting the most relevant area
Thus municipalities can now apply for funding to identify the boreholes at greatest risk. To meet this aim, Ramboll has developed a special tool "BNBO-Tool" which describes the risk in the individual wells.
The tool is designed to cover parameters such as geology, hydrology, land use and quantity of pumped water, which can be shown on a GIS-map.
"We plot all the various parameters and then we can quickly use a GIS spreadsheet to identify the most relevant areas for protection," explains Annette Raben, Head of Ramboll's Water Department.
The end product is a risk assessment which Ramboll prepares on the basis of the emerging data.
The tool was developed in collaboration with the environmental advisory company, ConTerra, which works with land use and agricultural data.
Facts on Danish groundwater
1 billion m3: The total available groundwater resource is 1 billion m3.
17%: Approx. 17% of rainwater permeates into groundwater and can later be pumped up again as drinking water. 60% evaporates and 20% flows back to streams and the sea, via drains, sewers and paved areas.
20-50 year-old groundwater: The groundwater we usually recover is between 20-50 years old. Denmark's oldest groundwater is in Kristrup near Randers, where the water is 15,000 years old.
100%: 100% of the Danish drinking water supply is based on groundwater.
653 million m3: The total groundwater recovery is around 650 million m3.