The Danish site-specific groundwater protection strategy

Transcription

1 The Danish site-specific groundwater protection strategy Richard Thomsen Chef Consult Geological Survey of Denmark and Greenland Ministry of Climate and Energy The Haque, the Netherlands june 2013

2 Denmark: 5.5 mill. inhabitants Area: km2 2/3 is farmland Water supply is decentralized Abstraction: ~ 700 mill. m3/year Water supply in Denmark

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4 1990 Contamination from urban development and agricultur imposes increasing threats to the groundwater resources and many bolehols were closed and protecting the groundwater got very high political attention To protect groundwater You need to know the position of the groundwater reservoir and how well the layers a bow protect the reservoir Clay protect better than sand

5 Introduction The water supply in Denmark is 100 % based on high quality groundwater. Complex and expensive treatment is not required. Groundwater protection is crucial. National strategy for groundwater mapping of 40 % of the country was initiated in 1999 to protect the groundwater The Danish Ministry of Environment is responsible for the groundwater mapping project, and for the preparation of actionplans for regulations for landuse and remediation of polluted sites During a 15 year period.the consumers have to pay 0.08 per m3 surcharge for the mapping. The total price of one m3 of drinking water is 7. Mapping cost is less than 2 % per m3. The total price for the project is

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7 Groundwater mapping and protection Major aspects of the national project: Mapping aquifers, vulnerability and groundwater quality Establishing geological and hydro geological models to Point out groundwater protection areas and establishing plans for future water supply

8 What is site-specific protection? The rationale for setting up site-specific groundwater protection zones is that some areas/geology are more vulnerable to groundwater contamination than others. The goal is thus to subdivide a given area according to the different potential of specific purposes and uses.

9 Idealized geochemical cross section showing how nitrate is reduced. The reduction depend on the clay content,redox and oxygenation. 2/3 of the nitrate leached disappear in the layers on its way to the water course Environmental Division Land-usel Planning and Groundwater Protection in Denmark, 2005 COUNTY OF AARHUS Side juni 2013 Århus Amt

10 1995

11 Measured resistivities for sediments in Denmark

12 Environmental Division Land-usel Planning and Groundwater Protection in Denmark, 2005 COUNTY OF AARHUS Side juni 2013 Århus Amt

13 Lolland Mapping with the SkyTEM-system Sand = groundwater Clay = no grundwater Cross section Resisti vity Borehole on cross section - detailed information right from ground surface to m s depth a b c d e sand saltwater clay borehole

14 Sustainable yield Based on geophysical mapping and 3D hydrological modeling yield was reduced 35%

15 Accuracy of aquifer mapping The geophysical mapping revealed completely unknown aquifers. Blue areas are thick aquifers and red show no aquifers

16 TEM and SkyTEM measurements TEM-data Data are collected by ground based systems since 1990 Data are collected by the airborne SkyTEMmethod since 2003 TEM data cover ~ 14,000 km 2 (july 2010)

17 Small survey volume Resistive volumes (> 80 ohmm)

18 The Egebjerg Case Calculated groundwater flow pathlines

19 The success of groundwater mapping and protection depend on: National standards, test-site and guidelines for geophysical measurements, boreholes and data interpretations Tools to make 3D interpretation of mapping data. National database to store: geophysical data boreholes data 3D models of geology for calculation of water abstraction and protection zones GEUS is responsible for national standards and national databases and guidelines for the national mapping project

20 Thank You for Your attention!