Abstract
As the drinking water supply in Denmark is totally based on groundwater, monitoring of the groundwater quality is extremely important to the Danish community. With more than 62% of the total land area under agricultural use the Danish Government has determined that the entire area is vulnerable to nitrate polution, and therefore the groundwater monitoring programme should cover the entire country. The Danish groundwater monitoring programme comprises water supply well monitoring, the groundwater monitoring network and agricultural watershed monitoring (Figs 1, 2) and is described on www.groundwater.dk. The programme is part of the National Action Programme for the Water Environment and Nature, NOVANA (Svendsen & Norup 2004; Svendsen et al. 2005). Groundwater quality monitoring is carried out on the basis of data from approximately 6200 public water supply wells. Furthermore, a detailed analytical programme is carried out on 1415 well screens from the monitoring network comprising 70 catchment areas, and on 100 shallow screens from the five agricultural watersheds (Svendsen et al. 2005). The detailed quality monitoring includes analyses for 97 chemical elements, comprising 26 main elements, 14 heavy metals, 23 organic micro-pollutants and 34 pesticides and metabolites.
Highlights
As the drinking water supply in Denmark is totally based on groundwater, monitoring of the groundwater quality is extremely important to the Danish community
Agricultural pesticides were detected in water samples collected from young groundwater in the agricultural watersheds, whereas in water samples collected in the groundwater monitoring network other pesticides, such as those used in consolidated areas like urban areas, roads or farmyards have been found
In 35% of the investigated wells, pesticides and their metabolites were recorded with values above the maximum admissible concentration (MAC) value for drinking water (0.1 mg per litre), whereas 11% of wells had more than ten times the MAC value
Summary
As the drinking water supply in Denmark is totally based on groundwater, monitoring of the groundwater quality is extremely important to the Danish community. The Danish groundwater monitoring programme comprises water supply well monitoring, the groundwater monitoring network and agricultural watershed monitoring (Figs 1, 2) and is described on www.groundwater.dk. Groundwater quality monitoring is carried out on the basis of data from approximately 6200 public water supply wells. The water supply wells generally have long screens and are intended to provide representative information on the distribution of the nitrate content in primary groundwater reservoirs. East of the glaciation borderline the sandy meltwater deposits and the pre-Quaternary limestone aquifers are generally covered by clayey till which reduces or prevents nitrate pollution (Fig. 3). Groundwater from the monitoring screens has been dated using the CFC (chlorofluorocarbon) content (GEUS 2004), and demonstrates that the highest nitrate values reflect the increase in the use of fertilisers (Fig. 4). Preliminary data suggest, that since 1979 farmers have adapted their spreading practice for fertilisers and manure such that nitrate pollution is following a declining trend
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