PART 4

 

Ground Water Quality

Groundwater quality on the Hungarian and Slovak territory is evaluated separately. The list of objects included in the joint monitoring is given in Table 4-1 and 4-2 and their position is presented in Fig. 4-1. From among the monitored objects representative objects for groundwater quality observation have been chosen on both sides for evaluation in the Joint Report. Detailed groundwater quality evaluation for each object included in the joint monitoring was done in the Slovak and Hungarian National Annual Reports on environmental monitoring in 2011. Monitoring data for the year 2011 in tabular form and the long-term graphical development of observed quality parameters for the period 1992-2011 creates the part of National Reports. On the negotiation of monitoring representatives held in 2007 it was agreed, that nitrites, TOC and silicates will be excluded from the groundwater quality parameter list, and that the groundwater quality will be evaluated for the period of calendar year.

Data from monitored objects are interpreted in relation to agreed limits for groundwater quality evaluation in the frame of intergovernmental Agreement from 1995. These limits were modified due to changes in national legislation. New limits have been approved by the monitoring representatives on the negotiation held on December 16, 2011 and are listed in Table 4-3.

4.1. Hungarian territory 

The subject of the joint groundwater quality monitoring on the Hungarian side consists of 22 objects, containing 16 observation wells and 6 wells that are used for drinking water supply (waterworks). While the observation wells have the screens situated in the upper part of the gravel sediments, the wells in waterworks draw the water from deeper horizons. The list of monitored objects is given in Table 4-1.

Data from wells that are used for drinking water supply are provided by Regional Waterworks Companies. The water quality monitoring in observation wells is carried out by the North-Transdanubian Inspectorate of Environment Protection, Nature Conservation and Water. The monitoring frequency in the year 2011 on 10 observation objects was twice a year, on remaining 6 observation object only once a year, and on waterworks 4 times a year.

In 2009 the observation of groundwater quality at object No. 9435 at Arak was terminated due to technical reasons. This object was replaced by the observation well No. 9544 at Halászi, which is situated close to the original object. 

Table 4-1: List of monitoring objects on the Hungarian territory

Well No. 9327, site: Dunakiliti

Based on long-term data seasonal, periodical variation of certain water quality parameters is markedly observed in the object No. 9327. Periodicity first of all appears in changes of water temperature, pH and nitrates concentrations. The groundwater has low salt content, similarly like the Danube water. Pollution by organic matter is rather balanced in last four years, in the evaluated year it was slightly higher than in the year 2010. Concentrations, however, do not exceed agreed limits. In case of phosphate ion concentration slight increase can be observed. In contents of nitrogen forms no substantial changes occurred in comparison with the previous year. Contrary to the year 2010 the iron content did not exceed the agreed limit. But the manganese content significantly exceeded the groundwater quality limit value in December (0.29 mg.l^-1). 

Well No. 9413, site: Sérfenyősziget

The water temperature is rather balanced and is not influenced considerably by meteorological conditions. The conductivity values after a temporary decrease (in the period 2001 -2003) has stabilised on certain level. In comparison with the year 2010 the conductivity values were higher and higher values were registered in case of chloride, sulphate and calcium concentrations. From the long-term point of view the calcium content exceeds 100 mg.l^-1, what is the limit value for this parameter, rather frequently. The content of ammonium and phosphate ions and the pollution by organic matter are below the limit values in long-term. In case of nitrates slight increase was recorded already in 2010, and in the evaluated year their concentration exceeded the agreed limit (52.4 mg.l^-1). Similar values occurred in the years 1997 and 2000. Slight exceeding of limit value was also recorded in case of iron (0.23 mg.l^-1). The content of manganese in groundwater is high and the measured contents exceeds the limit value for this parameter in long run. The decreasing tendency observed in recent years was interrupted by concentration of 0.75 mg.l^-1 recorded in December 2011.

Well No. 9430, site: Kisbodak

The groundwater in this object has a moderate salt content. The water temperature in the period of observation showed a slight seasonal fluctuation. The electric conductivity was similar to that in the previous year. The pH values in 2010 and 2011 slightly increased in comparison with the previous five years. The organic matter content show seasonal fluctuation, and it is below the limit value (3 mg.l^-1) in long-term. Low concentrations are characteristic for phosphates and nitrates in long-term. In case of ammonium ions no significant change was recorded, their content was similar to that in 2010 and it was lower than the limit value. The iron and manganese concentrations in the groundwater are high in this object and significantly exceed the limit values. Taking into account the long-term development of the manganese content a slight decrease can be observed. 

Well No. 9456, site: Ásványráró

The groundwater has a medium salt content and stable water temperature with slight seasonal fluctuation. In the long-term the electric conductivity has slightly increasing tendency. The organic matter content expressed by COD_Mn did not show significant changes and was below the limit values in long-term. The increasing tendency of ammonium ion concentrations stopped in 2008 and after slight decrease they have stabilised. In last three years they vary around 1.5 mg.l^-1 and significantly exceed the agree limit value (0.5 mg.l^-1). The content of nitrates and phosphates is low in long-term. The groundwater has high iron and manganese content, with seasonal fluctuation. Concentrations of these parameters in the evaluated year significantly exceeded the drinking water limit values, similarly to the previous period of observation.

From the above evaluation results, that the groundwater in shallow horizons of gravel sediments is enriched with iron and manganese. This also applies to other observation objects (wells), which were evaluated in the National Report. On some objects also increased contents of nutrients and organic pollution occur, what is related to local contamination of agricultural origin, or in some cases it comes from sewage ponds. On objects in the vicinity of pollution sources (e.g. outdated animal breeding), situated in the direction of groundwater flow, changes in groundwater quality associated with animal breeding can be well and sensitively observed. Outdated animal breeds are gradually disposed of, what is reflected in the improvement of groundwater quality (e.g. object No. 9458 at Ásványráró).

Inorganic and organic micro-pollution is monitored at selected objects (No. 9379, 9413, 9536, 9456 and 9480). In the year 2011 it was found in concentrations below the limit values for groundwater quality evaluation (Table 4-3).

The groundwater quality in deeper horizons of gravel sediments in the Szigetköz is monitored by production wells in waterworks. Wells in the region at Győr have higher content of ammonium ions, organic matter, manganese and iron in comparison with the other monitored wells. Manganese and iron concentrations exceed the limit values or approaching them. Concentrations are lower in wells where the water is drawn from greater depth. The water extracted in waterworks Dunakiliti I, Feketeerdő T-II and Darnózseli I is of satisfactory quality and the groundwater quality is characteristic with by stability.

In general the groundwater quality in wells producing potable water (occasionally after pre-treatment) is suitable for drinking water supply.

4.2. Slovak territory 

The groundwater quality monitoring on the Slovak territory is carried out on 18 objects (10 observation objects and 8 waterworks). Their list is given in Table 4-2. For purposes of the Slovak-Hungarian monitoring data of Western Slovakia’s Waterworks Company (ZsVS), the Waterworks Company Bratislava (BVS), Slovak Hydrometeorological Institute (SHMÚ) and Ground Water Consulting Ltd. (GWC) were used. Evaluation in the Joint Report is focused mainly on the groundwater quality in waterworks, which are more representative because of their continuous pumping. 

Table 4-2: List of monitoring objects on the Slovak territory

From among the waterworks three are situated on right side of the Danube (No. 102, 2559 and 907) and five on the left side (No. 119, 105, 103, 485 and 467), while the last two are located between the Danube old riverbed and the derivation canal. The groundwater quality in waterworks is stable in long-term. The waterworks Bratislava - Pečniansky les (No. 907) is influenced by the water quality in the Danube. Unlike the other waterworks most of parameters fluctuate and show seasonality. The groundwater quality on waterworks at Rusovce (No. 102) and Čunovo (No. 2559) improved since damming the Danube. The quality on waterworks at Kalinkovo (No. 119) and Šamorín (No. 105) is influenced by infiltration of surface water from the Danube and from the reservoir. The groundwater quality in waterworks at Gabčíkovo differs due to prevailing direction of groundwater flow, coming from the inland area. In waterworks at Vojka (No. 467) and Bodíky (No. 485) the groundwater quality is significantly influenced by local conditions.

Right side of the Danube

Waterworks at Rusovce – No. 102 and at Čunovo – No. 2559

The water quality had improved since damming the Danube mainly in waterworks at Rusovce. At present it is similar to water quality in waterworks at Čunovo. Concentrations of cations, anions and conductivity values on both waterworks fluctuate in a narrow range. Slight differences in parameters can be observed in case of hydrogen carbonates, calcium, magnesium, chlorides and in last three years also sulphates. These parameters reach higher values in waterworks at Rusovce, slightly lower is the content of potassium and nitrates. Higher concentrations of nitrates in the waterworks at Čunovo can be seen during the whole observation period, since 2008 they have decreasing tendency. However, in comparison with the groundwater quality limit value they are low. The contents of ammonium ions and phosphates are low in long run at both waterworks and mostly fluctuates below their detection limits. The organic contamination , expressed by COD_Mn, in last three years decreased. The manganese and iron concentrations are low in long-term. An exception is the high iron concentration recorded in the evaluated year (0.31 mg.l^-1), which exceeded the limit value. Similar value have not occurred since the monitoring started. The dissolved oxygen content fluctuates and it slightly increased in last five years. The groundwater quality parameters in long run satisfy the agreed quality limits for groundwater in both waterworks.

Waterworks at Bratislava No. – 907

With regard to the location of the waterworks Pečniansky les, near the Danube, the groundwater quality in the object No. 907 is significantly influenced by changes and fluctuation of chemical components in the Danube water. Values of individual parameters, particularly cations, anions, water temperature, dissolved oxygen content and nitrates concentration considerably fluctuate during the year. Dissolved oxygen content, nitrates concentrations and COD_Mn values are higher than at other observed objects. The COD_Mn values in last three years decreased below 1 mg.l^-1. Concentrations of manganese, ammonium ion and phosphates are below the detection limits of the applied analytical methods, or just above them in long-term.. Comparing to long-term data contents of the other parameters did not show significant changes in the evaluated year, and satisfied the agreed limits for groundwater quality. 

Left side of the Danube

Waterworks at Kalinkovo No. – 116 and at Šamorín – No. 105

The groundwater quality in waterworks situated on left side of the Danube was not influenced by damming to that extent like the quality in waterworks on the right side. The groundwater chemistry in waterworks at Kalinkovo (No. 119) and at Šamorín (No. 105) is similar and the course and changes of majority of groundwater quality parameters are also similar. Slightly higher values in waterworks at Kalinkovo occur in case of potassium, manganese and ammonium ion. Manganese contents occasionally exceed the limit value for this parameter. In the evaluated year it occurred in November, when the manganese concentration reached 0.55 mg.l^-1, what was slightly above the limit value. Manganese content in waterworks at Šamorín mostly occurs below the detection limit (<0.007 mg.l^-1). Dissolved oxygen contents have increasing tendency since 2007, and in the evaluated year they reached maximal values for the entire monitoring period at both waterworks (9.22 mg.l^-1 in Kalinkovo and 8.59 mg.l^-1 in Šamorín). In comparison with the previous period the pH values are slightly higher on both waterworks in last four years, and vary above the value of 7.5. The conductivity slightly decreased in the evaluated year. Concentrations of nitrates oscillate around 6 mg.l^-1 and phosphates occur in concentrations below the detection limit (<0.1 mg.l-1). Contamination by organic matter is low. In 2011 all observed groundwater quality parameters, except the only manganese concentration in Kalinkovo, satisfied the groundwater quality limits for drinking purposes at both waterworks.

Waterworks at Gabčíkovo – No. 103

The groundwater quality in Gabčíkovo waterworks differs from the groundwater quality in Kalinkovo and Šamorín waterworks due to the different groundwater flow direction. Increase of sulphates and chlorides contents shows that great part of the water flows to the waterworks from the inland part of Žitný Ostrov area. The water temperature in this waterworks is more balanced. The pH values after a temporary increase in the period 2006-2008 decreased and they returned to the level of the period 2000-2004. The dissolved oxygen contents are among the lowest ones. Nitrates concentrations in last four years oscillate around 4 mg.l^-1, similarly like in the period of years 2002-2005 (data from the period 2005-2007 are to be considered less representative due to adjustment and calibration of new apparatus). Concentrations of sodium, potassium and chlorides are the lowest from among the other observation objects, the sodium and potassium concentrations reach only half of values recorded in waterworks at Šamorín or Kalinkovo. The organic pollution, expressed by COD_Mn, is below the detection limit since 2002. Low in long-term are the contents of ammonium ion, phosphates, iron and manganese, which mostly oscillate at the level of detection limits of applied analytical methods. 

Waterworks at Vojka – No. 467 and Bodíky – No. 485

The groundwater quality in waterworks at Vojka and Bodíky is strongly influenced by local conditions. The groundwater chemical composition is similar on both waterworks; it noticeably differs in few components only. Slight differences occur in sulphates, nitrates, and occasionally chlorides, which are higher in waterworks at Vojka. The measured values of nitrates in the period 2005-2007 are considered as less representative because of above-mentioned reasons (change of apparatus for nitrates determination). For waterworks at Bodíky higher concentrations of ammonium ions, hydrogen carbonates and water temperature values are characteristic. Significantly higher in long-term are the manganese concentrations. They exceed the agreed limit in each determination, which was proved also in the year 2011. Dissolved oxygen content is low in long-term at both waterworks, and at Bodíky it is the lowest from among all evaluated waterworks. Slight improvement in redox conditions was registered in the period 2007-2011 in waterworks at Vojka (No. 467), where the dissolved oxygen content have slightly increased. Concentrations of manganese, ammonium ions, phosphates and iron are low at Vojka and mostly fluctuate below the detection limits. Such low concentrations at Bodíky are characteristic only for phosphates and occasionally for iron. The COD_Mn values are low in long-term at both waterworks, and since 2003 frequently below the detection limit.

Based on the above evaluation it can be stated that the groundwater quality in monitored waterworks is stable in long-term and mostly satisfies the agreed limit for drinking water. Exceeding of agreed limits occur in case of manganese and iron. The manganese content exceeds the agreed limit in waterworks at Bodíky in each determination and occasional also in waterworks at Kalinkovo. In 2011 only one manganese concentration at Kalinkovo was only slightly above the limit value. One iron concentration measured in waterworks at Rusovce also exceeded the limit value. Similar value have not occurred here since the monitoring started.

The groundwater quality in observation objects, that are evaluated in the National Report, is more influenced by local conditions. Monitoring results show that the agreed limits are exceeded more frequently compared to waterworks. Exceedings occur in case of ammonium ion, manganese and iron. Concentrations of all other analysed components of groundwater quality in observation objects satisfy the agreed limits for drinking water quality in 2011.

4.3. Conclusions 

Based on results of long-term groundwater quality monitoring on the Hungarian territory it can be stated that the groundwater in the upper part of the gravel sediments in Szigetköz is characteristic by higher iron and manganese content. The iron and manganese contents constantly exceed the groundwater quality limits on most of observation wells. On these objects also the concentrations of parameters indicating local pollution (parameters of nitrogen form and organic matter expressed by COD_Mn) are higher. The local pollution is of agricultural origin, or it originates from sewage ponds. In comparison with the previous year the contents of nutrients and organic matter slightly decreased or did not change.

Inorganic and organic micro-pollution of groundwater in 2011, monitored at selected observation objects, was found in concentrations below the limit values for groundwater quality evaluation (Table 4-3).

The groundwater quality in deeper horizons in the Szigetköz is monitored by wells used for drinking water supply. The iron and manganese concentrations are lower in wells, where the water is drawn from greater depth. In the region at Győr the iron and manganese contents exceed the drinking water quality limit values or oscillates around them. In these wells also the concentrations of ammonium ion and organic matter contents are higher. The water extracted in the northern part of Szigetköz (waterworks Dunakiliti I, Feketeerdő T-II and Darnózseli I) is of satisfactory quality and the groundwater quality is characteristic by high stability. In general the groundwater quality in wells producing potable water (occasionally after pre-treatment) is suitable for drinking water supply.

Based on results of long-term groundwater quality observation on the Slovak territory it can be stated that the observed groundwater quality parameters in waterworks mostly satisfy the agreed groundwater quality limits (Table 4-3). The exceptions are the waterworks at Bodíky and Kalinkovo. In waterworks at Bodíky the manganese exceeds the quality limit in each sampling and occasionally occurs a higher concentration of iron as well. In waterworks at Kalinkovo occasionally occurs manganese content, which does not meet the relevant limit (in 2011 once). In case of observation objects exceeding of limit values is more frequent and it occur at more objects.

Based on long-term measurements it can be stated that the organic pollution, expressed by COD_Mn, decreased during the observed period. From among nutrients the phosphates and ammonium ion occur in low concentrations on monitored objects in long-term. At present they are mostly below the detection limits of applied analytical methods. Only at Bodíky and Kalinkovo they reach higher concentrations, which do not exceed the limit values agreed for these groundwater quality parameters. The content of nitrates is low and the slightly increasing tendency observed since the year 2000 has stopped. In waterworks at Čunovo, decrease of nitrates to the level in years 1999-2000 was observed.

In the evaluated year 2011 no considerable changes of the groundwater quality were registered. The groundwater chemical composition in observation objects is similar to the groundwater chemical composition in waterworks in their neighbourhood. The groundwater quality in observation objects mostly reflects local influences.

Groundwater limits for drinking purposes used for evaluation in the frame of joint monitoring are given in the following table: 

Table 4-3: Groundwater quality limits for drinking purposes 

Basic parameters - physical and chemical parameters

Supplemental parameters – inorganic and organic micropollutants

HCH – hexachlorciclohexane