University of California

Presentations 2016

Thorling, Lærke

Presentation Title
Knowledge based protection of groundwater through monitoring and modelling of nitrate in groundwater in rural areas
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Cost efficient sustainable management of groundwater resources in rural areas calls for development of scientifically sound methods usable for mapping and monitoring as wells as dissemination of results to planners and the rural communities.There is a growing awareness in the political and agricultural communities that cost efficient measures to reduce the environmental impact of nitrate and pesticides in the future should be site specific and not only based on overall national regulation. Scientific developments in mapping methods in regard to hydrogeology and geochemistry are a prerequisite before this goal can be realized. Especially a better site specific knowledge of the nitrate reduction in the subsurface and aquifers is required in order to implement site specific measures. The Danish case is a strong example of the potential of the science policy interface to develop better resource efficiency. In Denmark groundwater is synonym with drinking water. To preserve this highly valued resource a national strategy for sustainable abstraction and groundwater protection has developed over the last 50 years. The National Groundwater Mapping Program has detailed mapped the hydro-geo-chemical settings of about 40 % of Denmark followed by delineation of nitrate vulnerable areas in drinking water abstraction areas. Strategic monitoring of the efficiency of implemented measures is part of the cost efficiency. Dating of groundwater has proved indispensable for interpretations. On a national scale regulations implemented by Danish farmers have succeeded in optimizing the nitrogen (N) management at farm level. Accordingly, since the 1980s the overall national upward trend of the nitrate concentrations in oxic groundwater has been reversed (Hansen et al., 2011). Locally, nitrate trend analyses in monitoring wells have shown a more varied pattern with both upward and downward nitrate trends underpinning the need for supplementary site specific groundwater protection initiatives. References:Hansen, B., Thorling, L., Dalgaard, T. & Erlandsen, M., 2011. Trend Reversal of Nitrate in Danish Groundwater – a Reflection of Agricultural Practices and Nitrogen Surpluses since 1950. Environmental Science & Technology, 45, 228-234. Schullehner, J. & Hansen, B., 2014, Nitrate exposure from drinking water in Denmark over the last 35 years. Environmental Research LettersHansen, Birgitte, and Lærke Thorling. 2008. “Use of Geochemistry in Groundwater Vulnerability Mapping in Denmark.” Geological Survey of Denmark and Greenland Bulletin 15: 45–48.Thomsen, R., Søndergaard, V.H. & Sørensen, K.I. 2004: Hydrogeological mapping as a basis for establishing site-specific groundwater protection zones in Denmark. Hydrogeology Journal 12, 550–562.

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