WGGW Bratislava – 26 October 2016 Trend Assessment in the National Groundwater Quality Monitoring Network in the Slovak Republic Robert Chriastel Robert.Chriastel@shmu.sk Slovak Hydrometeorological Institute Bratislava

Monitoring of Groundwater Quality in the Slovak Republic The main objectives Identification of significant pollution of GW within GW bodies, Identification of significant trends in concentrations of chemical compounds in GW caused by anthropogenic activities, Identification of significant trends in concentrations of chemical compounds in GW caused by natural process, Information source for decision making process in the field of water management, Fulfillments of other requirements of EU directives (characterization of GWB, monitoring of protected areas etc.).

Monitoring of Groundwater Quality in the Slovak Republic Monitoring programme Groundwater quality monitoring and assessment is performed since 1982 (till 2006 focused mainly on the important water management aquifers) Monitoring programme was redesigned in accordance with WFD requirements in 2007. Monitoring network: Consists of 545 sampling sites: - 132 in surveillance monitoring, - 413 in operational monitoring Sampling frequency: from 1 to 4 times per year - 1/year – Pre-Quaternary rocks (except karstic areas), - 2/year – Quaternary sediments, - 4/year – Karst (limestones and dolomites)

Monitoring of Groundwater Quality in the Slovak Republic Measured parameters: Measurement in situ: Depth of object, Temperature of air/water, Level of water before/during sampling, Strength of sampling pump, pH – value, Standardised conductivity, Oxygen content/saturation, Acid neutralisation capacity, Base neutralization capacity, Colour, Odour, Sediment content. Chemical analysis: Basic group of parameters – measured in every sampling site Supplementary group of parameters – measured based on identified pressures.

Monitoring of Groundwater Quality in the Slovak Republic Basic group of parameters: Basic physico-chemical substances: Natrium, Potassium, Calcium, Magnesium, Manganese, Iron, Ammonia ions, Nitrates, Nitrites, Chlorides, Sulphates, Phosphates, Silicates, Carbonates, Hydrogencarbonates, COD-Mn, forms of CO2, O2, pH-value Trace elements: arsenic, aluminium, cadmium, copper, lead, mercury, zinc, chromium, nickel Common Organic Compounds: TOC, nonpolar extractable substances (UV, IR), steam distillable phenols, humic substances Supplementary group of parameters: Basic physico-chemical substances: Hydrogen sulfides, total cyanides Common Organic Compounds: surfactants Specific Organic Compounds: Pesticides, ΣPCB, Aromatic hydrocarbons, Chlorinated phenols, Chlorinated dissolvents, Polyaromatic hydrocarbons

Monitoring network Layer of Quaternary GWB Layer of Pre-Quaternary GWB

Criteria for identification of significant and sustained upward trends: Statistically significant upward trend is detected and mean concentration of 2 last yearly mean concentrations ≥ 0,75 limit value (GW quality standard, threshold value). Statistically significant upward trend is detected and predicted concentration for 2021 ≥ limit value. Calculation of predicted concentration: Sen's estimate – data do not follows normal distribution Linear regression – data follows normal distribution

TREND ASSESSMENT Trend assessment is conducted only for those groundwater bodies, where at least one monitoring point showed occurrence of significant sustainable upward trend  required trend assessment at sampling site level. Time frame: 2004-2013 Minimum requirement for data sets: Minimum length of time series: 6 years; End of time series in 2012 or 2013; Maximum gap in time series: 1 year; Percentage of non-detects: LOQ < 50%. Treatment of LOQ values: Measurements bellow limit of quantification (LOQ) replaced by Max LOQ in each time series fulfilling minimum requirements (determinand/monitoring point); Measured values < Max LOQ replaced by Max LOQ .

ANOVA - if data set follows normal distribution; TREND ASSESSMENT Data aggregation On the sampling site level: calculation of mean concentration recorded within 1 year in individual monitoring point (parameter/monitoring point/year). On the GWB level: calculation of mean of annual mean concentrations of all monitoring sites located within the GWB. Detection of upward statistically significant trends ANOVA - if data set follows normal distribution; Mann-Kendall test - if data set do not follows normal distribution; Goodness-of-fit tests (Lilliefors test, Kolmogorov-Smirnov test); All tests are performed on 95% confidence level

TREND ASSESSMENT Percentage of statistically significant trends identified by individual tests Number of st. significant trends: 468

Výsledky hodnotenie trendov Trend assessment in groundwater: NH4

Trend assessment in groundwater: NO3

Trend assessment in groundwater: TOC

Trend assessment in groundwater: Cl

Trend assessment in groundwater SO4

TREND ASSESSMENT Preliminary trend assessment in GWB SK1000100P Average concentration of Cl- in sampling site 209090 (Záhorská Ves) is 6.3 times higher than the average concentration calculated for other sampling sites  significant influence on the overall trend assessment. Repeated assessments: Original dataset excluding results from sampling site 209090, data aggregation – mean of yearly means; Original dataset – all data, data aggregation – median of yearly means. Result – no st. significant trend  preliminary classification of trend rejected Preliminary trend assessment in GWB SK1000100P Average concentration of SO4 in sampling site 209090 (Záhorská Ves) is 6.1 times higher than the average concentration calculated for other sampling sites  significant influence on the overall trend assessment. Repeated assessments: Original dataset excluding results from sampling site 209090, data aggregation – mean of yearly means; Original dataset – all data, data aggregation – median of yearly means. Result – no st. significant trend  preliminary classification of trend rejected

TREND ASSESSMENT Preliminary trend assessment in GWB SK1000600P Average concentration of Cl- in sampling site 56090 (Bíňa) is 5.4 times higher than the average concentration calculated for other sampling sites  significant influence on the overall trend assessment. Repeated assessments: Original dataset excluding results from sampling site 56090, data aggregation – mean of yearly means; Original dataset – all data, data aggregation – median of yearly means. Result – no st. significant trend  preliminary classification of trend rejected Preliminary trend assessment in GWB SK1000600P Trend reversal assessment (two-section linear regression model)  no trend reversal found Classification of significant and sustained upward trend was accepted

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