1. GROUNDWATER QUALITY ASSESSMENT IN SLOVENIA (STATUS & TRENDS)
Environmental Agency of the Republic of Slovenia Marjeta Krajnc, Mojca Dobnikar-Tehovnik
23/02/2019

2. Groundwater in Slovenia
Slovenia: km2; alluvial aquifers: ca. 20% of area, karstic and fractured porosity aquifers: ca. 60% of area
Drinking water supply in Slovenia (% of inhabitants)
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3. Decree on the GW quality (OJ RS, 11/02) Main features
Limit values for 23 parameters of chemical status – environmental standards for GW
Statistical treatment of monitoring data (same as proposed by WG 2.8)
Criteria for the determination of : GW chemical status , long term trends of pollution, endangered GW bodies
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4. Decree on the GW quality Slovene standards
Limit values
Parameter
Unit
Drinking
water
Ground
Ammonium
mg NH4+/l
0,50
0,06
Potassium
mg K+/l /
10,00
Nitrate
mg NO3-/l
50,0
25,00
Individual pesticide
g/l
0,1
Atrazine
0,10
Pesticides
0,5
Mineral oils
µg/l
Tetrachloroethylene and trichloroethylene
10,0
4,00
Volatile halogenated hydrocarbons
Chromium
50,00
30,00
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5. GW quality monitoring (1) Monitoring network
INTERGRANULAR POROSITY AQUIFERS:
about 100 measuring sites on shallow alluvial aquifers, variable depth of filters;
3 measuring sites in deeper layers
Wells of waterwork stations
Private wells (in function or abandoned)
Borings
Piezometers
Automatic measuring stations (multilevel piezometers, on-line measuring NO3, T, pH, conductivity, O2)
KARSTIC AND FRACTIONED POROSITY AQUIFERS: 23 measuring sites, mostly springs
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6. GW quality monitoring (2) Sampling frequency & parameters analysed
GW quality monitoring since 1986
Sampling frequency: 2 – 4 times yearly
Analysed parameters: about 120 different physical and chemical parameters
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7. GW quality monitoring (3) Parameters analysed
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8. GW quality assessment before 2002
Separate quality assessment for alluvial aquifers and for springs
GW quality assessment for alluvial aquifers for individual sampling site as well as for the aquifer (arithmetic mean)
Yearly average results of analysed parameters for individual sampling site compared with limit values for drinking water (DW)
Results for priority parameters (nitrates, pesticides and AOX) for all sampling sites on alluvial aquifers shown on the maps of Slovenia
Long term trends for individual sampling site
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9. 23/02/2019

10. GW quality assessment according to Decree from 2002 on (1)
Determination of GW chemical status for the GWB (2002 – 2004 for aquifer)
Good chemical status:
CLAM < LV for every parameter of chemical status
CLAM: % confidence limit
Determination of long term trends for GWB
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11. GW quality assessment according to Decree from 2002 on (2)
Determination of endangered GWB:
one or more parameters
CLAM > LV (for nitrates CLAM > 2*LV) or
upward trend for three or more parameters
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12. GW quality monitoring network in Slovenia
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13. GW quality monitoring network: alluvial aquifers of central Sava river
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14. Nitrates 2002: comparison of results for 5 individual aquifers of central Sava river and group of aquifers Limit value (LV) for nitrates: 25 mg NO3- / l
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15. Atrazine 2002: comparison of results for 5 individual aquifers of central Sava river and group of aquifers Limit value (lV) for atrazine: 0,1 µg / l
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16. Long term trend determination
Arithmetic mean AM50 (AM0, AM100)
Linear regression
Significant trend: R2 > 0,5
Summation of parameters as pesticides or volatile halogenated aliphatic hydrocarbons:
conc. of individual compound < LOD   conc. of individual compound = 0
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17. Long term trend for atrazine: comparison of results for 5 individual aquifers of central Sava river and group of aquifers
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18. Problems of new GW quality assessment (1)
Problem #1: some GWBs have mixed types of aquifers (porous, fractured)
Problem #2: aquifers themselves are in most cases non-homogene, anisotropic 3D bodies
Problem #3: monitoring network on porous alluvial aquifers is heterogene (different kind of objects, different pumping rate, different depth and width of filters)  representativity of sampling sites for the whole GWB?
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19. Problems of new GW quality assessment (2)
Problem #4: representativity of monitoring network and status assessment on karstic aquifers or GW bodies
Problem #5: low number of monitoring objects on some GWB  to high scattering of results for statistical treatment
Problem #6: low density of monitoring objects  pollution might be “hidden”
Problem #7: in Slovenia monitoring on mostly shallow non-confined alluvial aquifers  more polluted than deeper confined layers and fractured aquifers  comparison between Member States?
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20. QUESTIONS
The purpose of GW immision monitoring – early detection of pollution by infiltration (pesticides and nitrates)?  monitoring of upper part of aquifer?
GW bodies are 3D entities - multilevel piezometers?
Aquifers are anizotropic, non-homogene bodies – density of piezometers?
Monitoring network on karstic aquifers – only springs?
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21. Conclusions
Delineation of GWB is of crucial importance for GWB quality assessment
For chemical status determination monitoring network has to be representative for the whole GWB
Combined approach (chemical status + evaluation of GW pollution on individual sampling site or sector) enables more effective pollution controll
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