PART 4

 

Ground Water Quality

4.1. Hungarian territory

The subject of the joint ground water quality monitoring on the Hungarian side consists of 22 objects, consisting of 16 ground water quality observation wells, situated in the upper part of the gravel sediments, and 6 wells that are used for drinking water supply (Tab. 4-1). Samples were taken 4 times during the year.

The water quality monitoring in observation wells was carried out by the North-Transdanubian Inspectorate for the Environment Protection and Water Management, the water quality monitoring in wells for drinking water supply was carried out by Regional Waterworks Companies. Wells included in the ground water quality monitoring are shown in Fig. 4-1. 

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

The ground water quality at above mentioned observation objects is described in details in the Hungarian National Annual Report in 2006. The long-term evaluation of the ground water quality, the detailed evaluation of the chemical composition, tables and diagrams are parts of it. In the Joint Annual Report four selected observation wells were evaluated. 

Well No. 9327, locality: Dunakiliti

Based on long-term data seasonal, periodical variation of water quality was markedly observed in the object No. 9327. The groundwater has low salt content, similarly as the Danube water. Periodicity appears mainly in changes of water temperature, conductivity, pH, nitrate, sodium and chlorides concentrations. Pollution by organic matter is not typical. No substantial change occurred in phosphate ion concentration, or it the content of nitrogen forms in comparison with the previous years. Iron and manganese in the water was detected in a concentration below the ground water quality limits. 

Well No. 9413, locality: Sérfenyősziget

The water temperature was not considerably influenced by meteorological conditions. Slightly decreasing tendency in conductivity values, observed in the previous period, remained in 2006 too. Concentrations of nitrogen forms, phosphate ions and concentration of organic matter are low, and compared to the previous year remained unchanged. The nitrite ion content on one occasion, in January, slightly exceeded the limit value. The manganese concentrations permanently exceed the limit value for drinking water quality. 

Well No. 9430, locality: Kisbodak

The temperature of this water, with a moderate salt content, showed slightly seasonal fluctuation, which followed the fluctuation of air temperature. The electric conductivity have not changed essentially, very slight increase can be observed in comparison with the previous years. The pH values showed a seasonal fluctuation, and the values are similar as in previous years. The organic matter content shoved a seasonal fluctuation as well, and values are below the limit values in long-term. No significant changes were recorded in case of nitrogen forms and phosphate ion concentrations, except the sample taken in May. The content of nitrites shows an increase. The iron and manganese concentrations in the ground water are high, significantly exceed the limit values. Considering the long-term development of the manganese content a slight decrease is observed. 

Well No. 9456, locality: Ásványráró

The ground water has a medium salt content and stable water temperature with a slight seasonal fluctuation. The slightly increasing tendency in electric conductivity values stopped. The organic matter content was below the ground water quality limit values and compared to the previous hydrological year no significant changes occurred. From among the nitrogen forms the increasing tendency of the ammonium ion concentration continued. The nitrite and nitrate content was low. The ground water had high, fluctuating iron and manganese content. Concentrations of these parameters exceeded the drinking water limit concentrations.

4.2. Slovak territory 

For purposes of the Slovak-Hungarian monitoring, the data of Western Slovakia’s Waterworks Company (ZVS), the Waterworks Company Bratislava (BVS), Slovak Hydrometeorological Institute (SHMÚ) and Ground Water Consulting Ltd. were used. The wells of the Waterworks Companies are used for drinking water supply; the other objects are observation wells (Tab. 4-2).

The evaluation for each well included in the joint monitoring, as in the previous years, was done for a period of fourteen years (1.10.1992-31.10.2006) in the Slovak National Annual Report in 2006. The evaluation in this report is focused mainly on the ground water quality in waterworks, which are more representative because of their continuous pumping. All data from each well were interpreted in relation to the agreed limits for drinking water, which are presented in Tab. 4.3.

In the year 2004 the pumping and observation on the object No. 116 (Kalinkovo, S-4) was stopped due to technical reasons and it was replaced by the well No. 119 (Kalinkovo, S-10). In the ground water quality evaluation data for both well are presented in 2006 as well. 

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

Short evaluation of the ground water quality in monitoring objects included in the data exchange according to the Agreement

In comparison with the previous year, there were no significant changes observed in parameters analysed during the hydrological year 2006. The ground water quality in drinking water sources has been very stable over the long term and mostly satisfied the agreed ground water quality limits. Exceedings of agreed limit values occurred at waterworks Bodíky and Kalinkovo in case of manganese, and at waterworks Kalinkovo in case of iron.

The ground water quality in observation objects is more influenced by local impacts. The monitoring results show that agreed limits are exceeded in case of ammonium ion, manganese and iron. Concentrations of all other analysed ground water quality components in observation objects satisfy the agreed limits for ground water quality.

Detailed evaluation of the waterworks and observation objects according to limit values for years 2005 and 2006 is given in the table “Exceedings of Standard’s limits in ground water quality parameters” in the Graphical Appendix of the Slovak National Annual Report in 2006. 

Ground water quality evaluation at waterworks

Right side of the Danube

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

The water quality at waterworks Rusovce and Čunovo is very similar after damming the Danube. Damming the Danube had a great influence on the ground water quality, primarily on waterworks at Rusovce, where the ground water flow direction had changed. After damming, concentrations of cations (sodium, calcium and magnesium) and anions (chlorides, sulphates and hydrogencarbonates) significantly decreased, which subsequently resulted in a permanent decrease of conductivity and the water chemical composition approximated the ground water chemical composition at Čunovo. Cations, anions and conductivity values had stabilised in the period 1996-2002 and at present they fluctuate at a narrow range. At the Čunovo waterworks the above mentioned decrease of cations and anions was registered as well, but in a less extent. Values had stabilised in 1998-1999. At both waterworks the nitrate concentrations decreased, however there is a slight increasing tendency observed since 2001. The content of other observed nutrients is low in a long term and mostly fluctuates at the level of their detection limits. At both waterworks the organic contamination, expressed by COD_Mn, decreased. The manganese and iron concentrations are low, and since 2002 in case of manganese they mostly fluctuate below the detection limit of the used analytical method. In the last two years (2005, 2006) slight increase of pH values and chloride concentrations and decrease of calcium and hydrogencarbonates was registered at both waterworks.

Waterworks at Bratislava No. – 907

The situation at waterworks Pečniansky les – object No. 907 is different in comparison to the other monitored waterworks. The water quality is significantly influenced by changes and chemical components fluctuation in the Danube water. Values of individual parameters fluctuate a lot during the year, except the pH value and partially potassium. The water temperature, dissolved oxygen and nitrate contents are the highest at this object, but they do not exceed the ground water quality limit values. Since 1999-2000 the nitrite and ammonium ion concentrations fluctuate below the detection limit of the used analytical method. The measured values show a slight increase of calcium, magnesium, and in last three years of sodium and chloride concentrations. Occasionally increased values of hydrogencarbonates, sulphates, calcium, electric conductivity (in hydrological years 1998, 2002 and 2003), magnesium (in 2003), sodium, chlorides (in 2004-2006) and silicates (in 2006) occurred. A slight decrease in manganese, phosphates and COD_Mn concentrations were observed. 

Left side of the Danube

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

The ground water quality at waterworks situated on the left side of the Danube was not influenced to the same extent by the damming as the quality at the waterworks on the right side. The ground water quality at waterworks Kalinkovo (objects No. 116 and 119) and at Šamorín (object No. 105) is similar and the course of most parameters is similar too. Some differences exist in calcium, potassium, manganese and hydrogencarbonates concentrations (details are given in the Slovak National Annual Report for the year 2006). In case of nitrate and sulphate contents long-term decrease had been observed on both waterworks. In case of nitrates it had stopped in 2001, in case of sulphates it stopped in 2004. Since then a slight increase is registered. The concentration of silicates continuously increased. The decrease in 2004 and 2005 is probably connected with changes in methodology, since the object owner has changed. The COD_Mn values rather fluctuate in the evaluated period, slight increase can be recognized up to 2001, since 2002 values slightly decreased and this tendency continued in 2006 as well. Slight increase was recorded in pH values in last two years. The increasing tendency of TOC values at both waterworks were replaced by their slight decrease in last three years.

Waterworks at Gabčíkovo – No. 103

The ground water quality at Gabčíkovo waterworks differs from the ground water quality at Kalinkovo and Šamorín waterworks due to the different ground water flow direction. The water temperature at Gabčíkovo waterworks is more balanced. In case of the conductivity values, the concentrations of calcium, sulphates, hydrogencarbonates and nitrates a slight long-term increase is registered. At the beginning of the whole observation period their concentrations were lower in comparison with the concentrations at Kalinkovo and Šamorín waterworks, but gradually they got to the same level. In the years 2004-2006 they also reached higher values. In comparison to the Kalinkovo and Šamorín waterworks the contents of chlorides, sodium and potassium in long-term reach lower values at object No. 103, on the other side contents of magnesium and silicates are little bit higher. The values of COD_Mn and TOC are lower at Gabčíkovo waterworks, however the difference is very small. Since 2002 the COD_Mn values mostly fluctuate below the detection limit of the used analytical method. Concentrations of phosphates, nitrites, ammonium, iron and manganese mostly oscillate at the level of detection limit.

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

The ground water quality at waterworks Vojka and Bodíky is strongly influenced by the local conditions. The ground water chemical composition is similar, it differs in few components only. The pH values at both waterworks vary in last two years, oxygen concentrations are low, chloride and sulphate contents have decreasing tendency since 2001 and the nitrate concentrations at object No. 485 (Bodíky) have the lowest values from among all waterworks included in the monitoring. At the beginning of the whole observation period significant differences were registered in nitrate and hydrogencarbonate concentrations, but they gradually disappeared. Considerable differences exist in concentrations of manganese, ammonium ion and silicates – these parameters are higher at Bodíky waterworks. The manganese, ammonium ion and iron concentrations at Vojka waterworks mostly fluctuate below the detection limit of the used analytical method. Since 2003 the concentrations of nitrite and COD_Mn are below the detection limits at both waterworks. 

4.3. Conclusions 

Based on the results of the long-term groundwater quality observation on the Slovak territory it can be stated that the observed groundwater quality parameters mostly satisfies the agreed ground water quality limits (Table 4-3). Sporadic exceeding of limit values were mentioned at the beginning of this chapter and detailed description can be found in the Slovak National Annual Report for the year 2006. The groundwater quality at waterworks is stable in long-term. Waterworks at Bratislava – Pečniansky les is influenced by the water quality in the Danube. Contrary to the rest of observed waterworks most of the groundwater quality parameters vary and show seasonality. In the region of waterworks at Rusovce and Čunovo the ground water flow direction have changed, which resulted in ground water quality improvement at mentioned waterworks. The groundwater quality at Kalinkovo and Šamorín is influenced by surface water infiltration from the Danube and reservoir. The ground water quality at Gabčíkovo waterworks differs from the other waterworks due to the prevailing ground water flow direction coming from the inland area. The ground water quality at Vojka and Bodíky waterworks is significantly influenced by the local conditions. At Bodíky the manganese content reaches higher values, more often exceeds the agreed ground water quality limit. In the hydrological year 2006 no considerable changes of the groundwater quality were registered. The ground water chemical composition in observation objects is similar to the groundwater chemical composition of the waterworks in their neighbourhood. The ground water quality in observation objects mostly reflects local influences.

According to the results of the long-term water quality observations at 16 groundwater quality observation wells on the Hungarian side, it can be stated that the water base of Szigetköz is typically characterised by a higher iron and manganese content. The iron and manganese content continuously exceed the groundwater quality limits on most of the observed wells. In general it can be stated that contents of nitrogen form parameters and parameters indicating the presence of organic matter (COD) slightly decreased or it did not changed in comparison to the previous year. Organic pollution is local, particularly of agricultural origin, or in some cases originates from waste water settlement tanks.

When analysing the ground water quality data from wells used for drinking water supply it is evident that the ammonium ion and organic matter contents are higher in wells at Győr region. In these wells also the iron and manganese contents exceed the drinking water quality limit values or oscillates around them. The iron and manganese concentrations are lower in wells, which are pumped from a bigger depth. The water extracted in waterworks Dunakiliti I., Feketeerdő T-II and Darnózseli I is of satisfactory quality and the ground water quality is characteristic by high stability. In general the ground water quality in drinking water producing wells (occasionally after pre-treatment) is suitable for a drinking water supply. 

Limits for drinking water quality used for evaluation in the frame of joint monitoring are given in the following table:

Table 4-3: Ground water quality limits for drinking water

EU-European standard, SK-Slovak standard, H-Hungarian standard

IV          – indicating value                    RV       – recommended value

LV         – limit value                            HLV    – highest limit value