GROUNDWATER MONITORING

1989-2008

Groundwater monitoring in Denmark has now taken place for about 20 years, with systematic sampling and reporting since 1989. The monitoring programme is presented in chapter 2. This report presents new data until 2008.

Since last reporting a substantial improvement in updating of the basic data on permits and well status for water works have taken place, as the municipalities now generally have access to the common national groundwater database JUPITER. A considerable backlog still remains in many municipalities on approval of chemical analysis from the abstraction wells. The responsibility for uploading of qualitative data lies at the laboratories, but the municipalities have the responsibility for the approval, which must take place before the data is assessable for withdrawal. In addition to this there exits a major backlog for the uploading of abstraction data on groundwater from 2007 and 2008. Significant improvement on the amount of groundwater soundings in JUPITER from the monitoring programme has taken place. A backlog exists on uploading all data from data logger measurements of groundwater heads from the quantitative monitoring programme, where dense time series are collected.

In order to judge the change of nitrate concentration in groundwater due to the implementation of the Water Action Plan in 1987 and the following legislation and action plans, one has to look at the youngest oxic groundwater. It appears that the nitrate concentration in the youngest groundwater is decreasing in the desired direction, and that the effects of the action plans now can be seen in groundwater. Statistical trend analyses were conducted on each monitoring point with oxic groundwater in the groundwater monitoring programme (GRUMO) and in the monitoring of agricultural catchments (LOOP). The results from GRUMO show that 82 % of the monitoring points with oxic groundwater have significant changes in the nitrate content at 95 % confidence level. This includes that the nitrate content has a significant decreasing trend in 62 % of the monitoring points in the youngest (0-15 years) groundwater. Only about 22 % of the monitoring points with older (25-50 years) groundwater show a similar significant decreasing trend. It must also be stated that many monitoring point in oxic groundwater in GRUMO have significant increasing nitrate contents. Totally, 41 % of the monitoring points with oxic groundwater have significant decreasing trends, 41 % has increasing trends and in 18 % there is no trend in the nitrate content. The results from LOOP show that 53 % of all monitoring points have significant decreasing trends in the nitrate content for the period from 1990 to 2008. Again it must be stressed that in LOOP some monitoring points in contrary have significant increasing nitrate contents over the entire monitoring period. It is suggested that the significant decreasing nitrate in the upper groundwater in LOOP is due to reduction in nitrate leaching and local hydrological conditions. It can be concluded that the nitrate content in groundwater is developing in the right direction, but that increasing nitrate to some extent occur even in young groundwater formed after the action plans implemented. Further investigations are needed to clear the picture. Only a few results from water supply wells exceed the MAC for drinking water. This is due to the fact that wells with nitrate above the MAC have been closed and often replaced by new deeper wells, so that polluted groundwater is not used for drinking water production. Nitrate thus diminishes the available groundwater resource.

An analysis of the phosphorous data form the entire monitoring period from LOOP shows that an important part of the phosphorus present in the upper groundwater is organic bound. As a consequence the phosphorus transport from agriculture to surface waters through groundwater may be larger than usually believed, as it is usually assumed that the phosphorus in groundwater is of purely geological origin.

In 2008 pesticides or their metabolites were found in almost 40 % of the sampled monitoring points (GRUMO), and the MAC of 0,1 µg/l for drinking water was exceeded in 11%. There is recognised an increasing presence of pesticides in groundwater at a national scale. Especially the upper groundwater layers carry pesticides and their metabolites, where as the pesticide content of deeper and older groundwaters are considerably lower. One explanation of the increasing amounts of findings in GRUMO since 2004 is that only monitoring points with groundwater formed after 1950 are sampled. But also the introduction of analysis of metribuzin (weed control in potatoes, banned since 2003) and its associated metabolites play a role. Metribuzin and its metabolites are not a part of the monitoring programme neither of waterwork abstraction wells nor of drinking water analysis. Glyphosate and its metabolite AMPA is found more frequently in waterwork wells than in the groundwater monitoring program. Glyphosate is the pesticide used in largest amounts in Denmark. It is primarily found in the upper and most vulnerable aquifers. In 2007 pesticides were found in 25 % of the active waterwork wells, and the MAC was exceeded in 5 %. With this the decreasing frequency of pesticide findings has ceased, and the frequency is again rising. As the water works do not include all of the pesticides with findings form the monitoring programme, probably more pesticides were found in the water works wells if these pesticides were included in their monitoring programmes. Today the larger waterworks primarily abstracts drinking water from aquifers with old groundwater. It is crucial for the future drinking water production whether the pesticides in the younger water are degraded before reaching these deeper aquifers. In urban areas it was found that pesticides are just as abundant as they are in rural areas. This must be seen in a context where the uses of pesticides in rural areas are much larger (in kg/ha) than in urban areas. This shows that there is a need for better understanding of the pesticide vulnerability in urban areas, where many pesticides are used on pavements, parking areas and other areas where all plants are undesired.

It has been necessary to correct the former reported data for groundwater abstractions . This is due to the fact that these data not only include actual data on abstractions, but also an estimate of abstraction from individual waterworks, irrigation etc, where no reporting had been given for a specific year. These estimates were made by the former counties, and as these estimates are no longer made, it is decided to exclude all estimates in the future and only report the actual data. This years report is thus not identical with earlier reporting. Data for abstraction shows that there has been an increase in irrigation the latest years probably due to very low precipitation rates in April/May.

In 2007 the national monitoring programme for groundwater level (piezometric heads) was establish based on diverse regional monitoring programmes in order to identify changes in the quantitative status of groundwater due to climatic change or abstraction of water. Groundwater heads are measured on a daily basis with data loggers. Time series show that there is a general rise in groundwater level since the late 1990s in both deep and regional aquifers. This is probably due to the decreasing abstraction rates at larger well fields, as a consequence of water savings and rising water prizes. This effect is most prevalent on Zealand and in the eastern parts of Denmark.

The national water balance model is developed and updated as a task under the NOVANA programme. The primary aim of the model is to develop a tool for evaluation of the water balance and groundwater recharge on larger catchment scale or for groundwater bodies. Another aim is to elucidate the size and the degree of the use of the groundwater resources dependent of climate, abstraction and land use. Details can be found in the technical guidance document for the hydrological modelling of NOVANA. The dense Danish mapping of groundwater resources in the areas of special drinking water interest has resulted in a large improvement of geological knowledge, which is being built into hydrogeological models. Also updating of data like streams, climate, water abstractions, outlet of wastewater etc. has been a major challenge, as well as the introduction of a more detailed grid. The homepage of the model www.vandmodel.dk has been revised, and the status and results of the current updating can be found together with examples of the use of model results.

1989-2007

Groundwater monitoring in Denmark has now taken place for about 20 years since 1989. This report presents new data from 2007 and for the first time The National Monitoring Programme for Groundwater Levels is reported.

Since 2007 there have been considerable problems with the technical transmission of data from the former counties, the laboratories and the municipalities to the national groundwater database JUPITER. This is due to a total reorganisation of the data transfer for chemical analyses of groundwater and drinking water, water abstraction and measurements of the groundwater table. Data from 2006 and 2007 are thus incomplete. Many municipalities have not yet adapted regular procedures for data handling in JUPITER, especially for data on abstraction of groundwater. The responsibility for uploading of qualitative data lies at the laboratories, but the municipalities have the responsibility for the approval, which must take place before the data is assessable for withdrawal.

In order to judge the change of nitrate concentration in groundwater due to the implementation of the Water Action Plan in 1987 and following legislation and action plans, one has to look at the youngest groundwater. It appears that the nitrate concentration in the youngest groundwater is developing in the desired direction and that the effects of the action plans now can be seen in the groundwater. The highest nitrate concentrations are in groundwater formed in the mid 1980s and a small decrease is found thereafter, indicating that changed agricultural practice has an effect on groundwater quality. This covers large variations in agricultural practice, soil type, crops etc, but in the youngest groundwater more wells have decreasing nitrate content compared to prior to the action plans. It can be concluded that the nitrate content in groundwater is developing in the right direction. Only a few results from water supply wells exceed the MAC for drinking water. This is due to the fact that wells with exceedences have been closed and often replaced by new deeper wells, meaning that polluted groundwater is not used for drinking water production. Nitrate thus diminishes the available groundwater resource.

Pesticides and their metabolites are mainly found in shallow groundwater or younger groundwater. They are found in almost 40 % of the well screens in groundwater monitoring areas, and in almost 15 % of the screens the concentrations are above MAC for drinking water of 0.1 µg/l. Monitoring of pesticides and their metabolites now only occurs in screens with groundwater formed after app. 1950. A higher number of findings have appeared since 2004, when metribuzin (herbicide used in potato production, banned in 2003) and associated metabolites were included in the monitoring programme. Metabolites of metribuzin were in some areas found in more than half of the analysed screens (in 25 out of 45). Metribuzin and its metabolites are not a part of the control programme of water works abstraction well nor of the drinking water analysis. Glyphosate and its metabolite AMPA is found more frequently in water work wells than in the groundwater monitoring programme. Glyphosate is the pesticide used in largest amounts in Denmark. It is primarily found in the upper and most vulnerable aquifers. In 2007 pesticides were found in 25 % of active water works wells, and the MAC was exceeded in 4 %. With this the decreasing frequency of pesticide findings have ceased and the frequency is again rising. As the water works do not include all of the pesticides with findings form the monitoring programme, probably more pesticides were found in the water works wells if these pesticides were included in their monitoring programmes. Today the larger water works primarily abstracts drinking water from aquifers with old water. It is crucial for the future drinking water production whether the pesticides in the younger water are degraded before reaching these deeper aquifers.

During the last six to seven years between 600 and 700 million m³ of groundwater has been abstracted annually. Abstraction from water works for drinking water purposes accounted for 65 % of the total groundwater abstraction, while irrigation and fish farming are assigned for 26 %. There is an urgent need to improve the reporting of water abstraction to the JUPITER database. These data are critical for the evaluation of the quantitative state of the groundwater bodies, and especially for estimation of the impact from irrigation on dependent ecosystems in streams and wetlands.

In 2007 the national monitoring programme for groundwater level (piezometric heads) was establish based on diverse regional monitoring programmes in order to identify changes in the quantitative status of groundwater due to climatic change or abstraction of water. Groundwater heads are measured on a daily basis with data loggers. Time series show that there is a general rise in groundwater level since the late 1990s in both deep and regional aquifers. This is probably due to the decreasing abstraction rates at larger well fields, as a consequence of water savings and rising water prizes. This effect is most prevalent on Zealand and in the eastern parts of Denmark.

The national water balance model is developed and updated as a task under the NOVANA programme. The primary aim of the model is to develop a tool for evaluation of the water balance and groundwater recharge on larger catchments scale or for groundwater bodies. Another aim is to elucidate the size and the degree of the use of the groundwater resources dependent of climate, abstraction and land use. Details can be found in the technical guidance document for the hydrological modelling of NOVANA. The dense Danish mapping of groundwater resources in the areas of special drinking water interest has resulted in a large improvement of geological knowledge, which is being built into hydrogeological models. Also updating of data like streams, climate, water abstractions, outlet of wastewater etc. have been a large challenge, as well as the introduction of a more detailed grid. The homepage of the model www.vandmodel.dk has been revised, and the status and results of the current updating can be found together with examples of the use of model results.

1989-2006

Groundwater monitoring in Denmark has now taken place for about 15 years. Due to the Structural Reform of Government in 2007 there was no reporting in 2006, and thus this years report includes new data from 2005 and 2006. Please note, that there has been considerable problems with the technical transmission of data from the former counties, the laboratories and the municipalities to the national groundwater database JUPITER. This is due to a total reorganisation of the data transfer for chemical analyses of groundwater and drinking water, water abstraction, and soundings of the water table. Data from 2006 are thus incomplete. Chemical analyses from water works wells for 2006 from several counties are still not uploaded to JUPITER. All kind of chemical laboratory data form all parts of the country from the last part of 2006 are missing, because the laboratories yet have not succeeded in uploading the data. This concerns chemical analyses from water works wells, monitoring wells and data from other investigations of groundwater quality. Finally no data are reported from the municipalities on groundwater abstraction in 2006.

In order to judge the change of nitrate concentration in groundwater due to the implementation of the Water Action Plan in 1987 and following legislation and action plans, one has to look at the youngest groundwater. It appears that the nitrate concentration was at its highest in groundwater formed in 1985. A decrease in nitrate concentration can be seen in the youngest groundwater formed after 1985, a decrease that is probably due to changes in agricultural practices after the Water Action Plan was implemented. Today the average nitrate concentration in the oxidised zone - the youngest groundwater - lies under the Maximal Admissible Concentration (MAC) for drinking water (50 mg/l). Though this covers large local variations, it is noteworthy that the share of very large nitrate concentrations has decreased in the youngest water. It can be concluded, that the development of the nitrate content in groundwater is going in the right direction. Only a few results from water supply wells exceed the MAC for drinking water. This is due to the fact that wells with exceedences are closed and often replaced by new deeper wells, meaning that polluted groundwater is not selected for drinking water production. Nitrate thus diminishes the available groundwater resource.

The major part of dissolved phosphorous in groundwater is of geological origin, and no great changes have taken place since 1987. The largest concentrations are found in reduced groundwater. As most phosphorous precipitates by simple water treatment, phosphorous as a whole is not a drinking water problem. In private wells without water treatment, abstraction is from the uppermost groundwater, and therefore a high content of phosphorous can occur due to pollution from above. However, groundwater with a phosphorous content feeds into fjords etc. and can contribute to oxygen depletion in these marine waters. The size of this contribution is not known at this point of time.

In some drinking water wells in some areas high values of nickel and arsenic occur. Both substances occur naturally in groundwater, but occur under different chemical conditions, especially oxidation state. Nickel occurs where pyrite is oxidised due to overexploitation of groundwater aquifers. The natural content of arsenic is largest in reduced groundwater, where the groundwater has been in contact with tertiary marine sediments or quaternary sediments with a marine clay content. Nickel and arsenic in groundwater limits the size of the groundwater resource available for drinking water purposes. Both these substances are held back to some extent in the water works filters and are mostly not a problem for the drinking water quality. Though in some regions and indeed in private households with own well and no water treatment, exceedences of MAC do occur.

In groundwater monitoring areas the percentage of well screens with pesticides or their metabolites, above and below the MAC of 0.1 ìg/l for drinking water has increased once again since 2004. One of the reasons for this is the fact that monitoring for pesticides and their metabolites now only occurs in screens with young groundwater. Besides this, metribuzin (herbicide used in potato production, banned in 2003) and associated metabolites were included in the 2004 monitoring programme. Metabolites of metribuzin were in a single county found in more than half of the analysed screens (in 25 out of 45). Metribuzin and it's metabolites are not a part of the water works abstraction well or drinking water control programme. The declining occurrence of pesticides and their metabolites in groundwater abstraction wells for drinking water production continues. The lower occurrence is due to the fact that wells with content of pesticides and metabolites are closed down. Today the larger water works primarily abstracts drinking water from aquifers with old water. It is crucial for the future drinking water production whether the pesticides in the younger water are degradated before reaching these deeper aquifers.

During the last 6 to 7 years the yearly abstraction of groundwater in Denmark has been between 600 and 700 million m3. Abstraction from water works for drinking water purposes accounted for 65 % of the total groundwater abstraction, while irrigation and fish farming assigned for 26 %.

The former DK-model for water balance and water resources in Denmark is currently updated and developed, and is in its new form called the NOVANA model . The primary aim of the model is, to develop a tool for evaluation of the water balance and groundwater recharge on a larger catchments scale or for groundwater bodies. An other aim is to elucidate the size and the degree of the use of the groundwater resources dependent of climate, abstraction and land use. Details can be found in the technical guidance document for the hydrological modelling of NOVANA.
In 2005 - 2006 the most important task of the modelling was to collect knowledge and data from the counties, before they closed down, with special focus on updating the geological model. The work has focused on
a) Geological updating making a 1. version geological model for Zealand, Fynen and Jutland from the boarder to Limfjorden. Quality securing of the geological model of Zealand is done over the summer 2007.
b) Numeric model . A Numeric model is set up for Fynen and Zealand, and is ongoing on central Jutland. The calibration of the Fynen model is almost done, while the calibration for the Zealand model is ongoing.

1989-2004

Groundwater monitoring has taken place for about 15 years. This year the report is based on data from the new and changed monitoring programme, NOVANA.

In order to judge the change of nitrate concentration in groundwater due to the implementation of the Water Action Plan in 1987 and later changes in the nitrate load, one has to look at the youngest groundwater. It can be seen that the nitrate concentration was at its highest in 1985. A decrease in nitrate concentration can be seen in the youngest groundwater after 1985, a decrease that is probably due to changes in agricultural practices before as well as after the Water Action Plan was implemented. The average nitrate concentration in the oxidised zone - the youngest groundwater - now lies under the Maximal Admissible Concentration (MAC) for drinking water (50 mg/l). It can be concluded, that the development of the nitrate content in groundwater is going in the right direction. However a large proportion of the groundwater that is monitored is older than the implementation of the Water Action Plan, which is why no development in nitrate concentrations can be seen.
Only a few results from water supply wells exceed the MAC for drinking water. This is due to the fact that wells with a too high concentration of nitrate are closed and new deeper wells are established, meaning that polluted groundwater is not used for drinking water production.

The major part of dissolved phosphorous in groundwater is of geological origin, and no great changes have taken place since 1987. The largest concentrations are found in reduced groundwater and originate from marine interglacial deposits. As most phosphorous precipitates by simple water treatment, phosphorous as a whole is not a drinking water problem. In private wells without water treatment, abstraction is from the uppermost groundwater, and therefore a high content of phosphorous can occur due to pollution from above. However, groundwater with a phosphorous content feeds into fjords etc. and can contribute to oxygen depletion in these marine waters. The size of this contribution is not known at this point in time.

In some drinking water wells in some areas high values of nickel and arsenic occur. Both substances occur naturally in groundwater, but occur under different chemical conditions, oxic and anoxic conditions. Nickel occurs where sediments with some pyrite content are oxidised (overexploitation of groundwater aquifers), whereas arsenic is released in reduced groundwater, where the groundwater has been in contact with tertiary marine sediments or quaternary sediments with a marine clay content. Nickel and arsenic in groundwater deplenishes the size of the groundwater resource available for drinking water purposes. These substances are held back to some extent in the water works filters and are usually not a problem for the drinking water quality.

In groundwater monitoring areas the percentage of well screens with pesticides or their metabolites, above and below the MAC of 0.1 µg/l for drinking water has increased once again. One of the reasons for this in 2004 is the fact that monitoring for pesticides and their metabolites now only occurs in screens with young groundwater. Besides this, a substance called metribuzin (herbicide used in potato production, banned in 2003) and metabolites hereof were included in the 2004 monitoring programme. Metabolites of metribuzin were in a single county found in more than half of the analysed screens (in 25 out of 45).
Metribuzin and it's metabolites are not a part of the water works abstraction well or drinking water control programme. The declining occurrence of pesticides and their metabolites in groundwater abstraction wells for drinking water production continues in 2004. The lower occurrence is due to the fact that wells with content of pesticides and metabolites are closed down.

During the last 6 to 7 years the yearly abstraction of groundwater in Denmark has been between 600 and 700 million m³. From 2003 to 2004 a rise of 30% in groundwater abstraction for crop irrigation has occurred. This rise is from 141 million m³ to 189 million m³ per year. This rise was due to a lower precipitation in the early summer months.

1998-2003
The current report emphasises the period 1998-2003 in which the monitoring programme, NOVA 2003, has been operating. This time span was chosen in order to ensure data comparison and time series evaluation on the basis of a consistent analysis programme.

Grundvandsovervågning 1998-2003 (Groundwater monitoring 1998-2003) presents data from 70 national groundwater monitoring areas (GRUMO), 5 agricultural watershed catchment areas (LOOP) and several thousands water abstraction wells, thereby providing a comprehensive picture of groundwater quality in Denmark.

The Action Plan for the Aquatic Environment was approved in 1987. As the age of groundwater in the majority of well screens predates 1990, recognition of any overall effect of the Action Plan on nitrate content in groundwater is generally not possible. However, nitrate content seems to be declining in the youngest groundwater. As average concentrations are still well above Maximum Admissible Concentration (MAC) for drinking water (50 mg/l), it must be concluded that things are moving in the right direction. We do not know, however, if efforts to reduce nitrate concentration in groundwater have been sufficient so far. Furthermore, an investigation of small private water supplies shows that the uppermost groundwater is heavily influenced by nitrate since water in more than 20% of the investigated dug or drilled wells exceeds MAC. However, a part of these high values may be related to unfavourable well construction or location.

Data from 1998-2003 shows that nitrate concentration in about 16% of monitoring screens exceeds MAC for drinking water. Presently, only 1.1% of water abstraction wells contain nitrate concentrations exceeding MAC for drinking water due to abandoning and subsequent replacement of most wells showing high nitrate concentrations, by deeper wells. More than 40% of screens in monitoring areas, and approximately 75% of groundwater abstraction wells do not contain nitrate (less than 1 mg/l).

There are no changes in content of dissolved phosphorus in groundwater for the period 1998-2003. Phosphorus of geological origin can be measured in concentrations above MAC (0,15 mg/l) in some regions of Denmark. This occurs more frequently in deeper aquifers with reduced groundwater where groundwater chemistry is influenced by interglacial marine deposits. A high phosphorus content is generally not a problem in relation to drinking water quality as it usually precipitates in sand filters at the waterworks.

Inorganic trace elements occur naturally in groundwater in Denmark. Where pH is low, some of these elements such as aluminium may occur in high concentrations. In aquifers with no oxygen content, arsenic may be abundant in high concentrations. The presence of inorganic trace elements near MAC for drinking water, however, may also be caused by anthropogenic activities such as contamination, lowering of groundwater level, etc.

In general, the MAC of many inorganic trace elements has been exceeded in all elements of the groundwater monitoring programme. From 1998-2003, the MACs have been exceeded in 32% of screens in the monitoring areas. In agricultural watershed catchment areas, where young and shallow groundwater is surveyed in areas with intensive agriculture, results are conspicuous with many high nickel, zinc, lead and arsenic values. Within groundwater monitoring areas and in water abstraction wells, arsenic in particular was found in high values. In major water works with effective sand filters, inorganic trace elements will partly precipitate and will not necessarily have a negative effect on drinking water quality. However, in smaller water supplies without water treatment facilities, they may form a water quality problem.

Organic micro pollutants have been found in 92% of well screens in groundwater monitoring areas from 1993-2003. By excluding anionic detergents (due to a non-specific method of analysis), organic micro pollutants are detected at least once in 63% of well screens. The percentage for agricultural watershed catchment areas is 56 and approximately 20% for water abstraction wells (also without anionic detergents). However, the concentration of these compounds is below the MAC for drinking water in most groundwater abstraction wells, as well as in most well screens in groundwater monitoring areas.

The percentage of well screens with pesticides and/or their metabolites in groundwater monitoring areas was approximately 27 in 2001, 2002 and 2003. The percentage of well screens with concentrations above the MAC for drinking water (0,1 µg/l) was about 8.5 in both 2001 and 2002, but increased to about 10% in 2003. Pesticides or their metabolites were detected in more than 40% of well screens sampled from 1998 until 2003, and the share above MAC was about 15%.

The metabolite 2,6-dichlorbenzamide (BAM), a degradation product of chlorthioamide and dichlobenil, and triazins and their metabolites, notably deethylisopropylatrazine, are the most commonly detected compounds. The detection of deethylisopropylatrazine has increased to 9% of wells sampled. This metabolite was detected in more than 30% of monitoring at shallow depth below agricultural watershed catchment areas. The metabolite was detected in about 3% of analysed water supply wells. Only about 200 water supply wells were analysed for this metabolite, and it is anticipated that detection will increase as analyses are performed on an increasing number of water supply wells.

Groundwater abstraction wells are still severely affected by pesticides or metabolites. During the period from 1998-2003, the percentage of detections was approximately 26; 6% exceeded MAC. During the same period, the annual percentage of wells with concentrations exceeding MAC, declined from 10 to 5%. In 2003, pesticides or their metabolites were detected in about 27% of the wells.

The most commonly detected compounds in water abstraction wells are BAM, atrazine and triazine-metabolites as well as mechlorprop and dichlorprop. From 1998-2003, pesticides or their metabolites have been detected in more than 50% of sampled shallow (0-20 mbgs) groundwater abstraction wells. Like in groundwater monitoring areas, occurrences decrease with increasing depth.

The metabolite BAM often appears in combination with other pesticides and metabolites in shallow aquifers, and can, accordingly, be used as an indicator for other pesticides, for example in small private dug or drilled wells, as these often abstract shallow groundwater.

The total groundwater abstraction for drinking water production was 403 million m3 in 2003. When the monitoring programme started in 1989, the amount was 640 million m3, so abstraction has been reduced by 37%. In 2003, abstraction for irrigation was 141 million m3, and this is one of the lowest recorded figures in the monitoring period.

Groundwater models and hydrological models are being used significantly to estimate groundwater recharge and capture zone. Stream models have been developed for 84% of groundwater monitoring areas, and this has resulted in a revision of areas of influence for about one half of these.

Further info (in Danish)

"Grundvandsovervågning 2003 " (Groundwater monitoring 2003) presents data from the national groundwater monitoring areas (GRUMO), the agricultural watershed catchment areas (LOOP) and water abstraction wells, and thereby provides a comprehensive picture of groundwater quality in Denmark. The data mainly represents the period from 1989 to 2002.

The Action Plan for the Aquatic Environment was approved in 1987. As the age of the groundwater in the majority of well screens predates 1990, it is generally not possible to recognise any effect of the Action Plan on the nitrate content of groundwater. However, the nitrate content seems to be declining in the very youngest groundwater sampled in sandy agricultural catchments. The average concentrations are still well above the maximum admissible concentration (MAC) for drinking water (50 mg/l).

The age of groundwater in 39 monitoring well screens in the groundwater monitoring areas is younger than 1987 (6-8 years old), and thus provide an indication of the affect of the Action Plan on nitrate concentrations in groundwater. The monitoring data from these well screens show ambiguous variations, but the nitrate content seems to be declining in 1/3 of these well screens.

Half of the monitoring wells in the groundwater monitoring areas are screened in primary aq- uifers, and about 75% of the water abstraction wells do not contain nitrate (less than 1 mg/l). The nitrate concentration in about 16% of the monitoring screens exceeds the MAC for drinking water. This is the same as was observed in 2001 and 2002. Presently, only 1.1 % of the water abstraction wells contains nitrate concentrations that exceed the MAC for drinking water as most wells with nitrate concentrations have been abandoned and replaced with deeper wells.

Inorganic trace elements occur naturally in groundwater in Denmark. Where pH is low some of these elements as aluminium may occur in high concentrations. In aquifers without oxygen arsenic may be abundant in high concentrations. But the occurrence of inorganic trace elements near the MAC for drinking water may also be due to anthropogenic activities such as contamination, lowering of the groundwater level etc. Generally high contents of inorganic trace elements in the groundwater may impact the water quality of natural springs, streams and lakes if these are feed by groundwater. High concentrations of e.g. nickel, lead and arsenic have been detected in the uppermost groundwater in LOOP areas and these elements may be spread throughout the aquatic environment. But the dynamics of the spreading of these elements is not well described.

There is an increase in the number of water abstraction wells with nickel concentrations that exceed the MAC for drinking water in all analysis. It appears that the problem with high nickel concentrations in groundwater is increasing in some parts of Denmark.

As expected the numbers of arsenic analysis of groundwater from water abstraction wells is increasing due to the regulatory requirements established in 2001. The availability of arsenic data is still not evenly spread out through the country, but a tendency of the concentrations above the MAC for arsenic exists in areas with tertiary marine clays, either in the subsurface or in till. Younger marine deposits may also be a source of arsenic.

In major water works with well effective sand filters, inorganic trace element will partly be fixed and will not necessary have a negative effect on the drinking water quality. However, in smaller water supplies without water treatment, they may constitute a quality problem.

Organic micro pollutants have been found in 91% of the well screens in the groundwater monitoring areas in the monitoring period. If the anionic detergents are excluded (due to a non-specific method of analysis), then organic micro pollutants are detected at least once in 59% of the well screens. Data have shown that organic micro pollutants can readily be transported to depth in aquifers and aquitards. For example, the pollutant trichlormethan has been found at depths exceeding 60 meters below ground surface (mbgs). However, the occurrence of these compounds is mainly limited to wells screens at depths between 0 to 40 mbgs.

Organic micro pollutants (excluding anionic detergents) have been detected at least once in 20% of the water abstraction wells which were sampled. However, the concentration of these compounds is below the MAC for drinking water in most of the groundwater abstraction wells, as well as in most well screens in the groundwater monitoring areas.

The number of well screens with pesticides and/or their metabolites in the groundwater monitoring areas was approximately 27% in both 2001 and 2002. The number of well screens with concentrations above the MAC for drinking water (0,1 µg/l) was about 8.5% in both years. Pesticides or their metabolites have been detected in more than 40% of the well screens sampled during the period from 1990 until 2001.

The metabolite 2,6-dichlorbenzamid (BAM) (degradation product of chlorthiamid and dichlobenil), and the triazins and their metabolites, especially deethylisopropylatrazine, are the most commonly detected compounds. The detection of deethylisopropylatrazine has increased to 8.4% of the wells sampled. This metabolite is detected in more than 30% of monitoring wells that are completed at shallow depth below the agricultural watershed catchment areas. The metabolite was detected in about 3% of the water supply wells analysed. Only about 200 water supply wells were analysed for this metabolite, and it is anticipated that their detection will increase as analyses are made in an increasing number of water supply wells.

Groundwater abstraction wells are still severely affected by pesticides or metabolites. During the period from 1997 to 2002 the number of detections has varied by about 30%. During the same period, the number of wells with concentrations exceeding the MAC has declined from 10% to 7%. In 2002 pesticides or their metabolites were detected in more than 50% of the shallow (0 to 20 mbgs) groundwater abstraction wells sampled. As in groundwater monitoring areas, their occurrence decreases with increasing depth.

An estimation of the ground water abstraction in 2002 compared to the wells being analysed shows that 36.7% of the abstracted groundwater contains pesticides and/or metabolites. The percent of the abstraction exceeding the MAC was only 4,2% which indicates, that the water works have been forced to close a large number of wells with concentrations above the MAC.

Groundwater levels were high in 1994-95 and again in 2000-2002 due to unusually high lev- els of precipitation. Groundwater levels were very low in 1995-1997 due to very low winter precipitation during this period.

A thematic report on the entire freshwater cycle points out, that the resource is being over exploited in several areas of the country, resulting in excessive streamflow depletion. Nationally, the resource is sufficient compared to the abstraction in 2002, but the abstraction is not regionally balanced. Groundwater is being over-exploited in the greater Copenhagen, Odense and Århus areas. This may results in the degradation of the quality of groundwater and surface water.

Further info (in Danish)