EAF - GW 2001-11-23 The EU Water Framework Directive: Statistical aspects of the identification of groundwater pollution trends, and aggregation of monitoring results Financed by: Federal Ministry of Agriculture, Forestry, Environment and Water Management - Austria European Commission, DG Environment in kind contributions by partner countries Project co-ordination Federal Environment Agency - Austria 03.04.2000

Partners and observers involved Federal Environment Agency, Austria Administration for Environment, Nature, Land and Water Management, Belgium Geological Survey of Denmark and Greenland, Denmark Agence de l ’eau Artois Picardie, France Hessisches Ministerium für Umwelt, Landwirtschaft und Forsten, Germany Institute of Geology and Mineral Exploration, Greece EPA - Environmental Protection Agency, Ireland RIVM-Nat. Institute for Public Health and the Environment, The Netherlands Instituto da Água, Portugal Ministerio de Medio Ambiente, Spain Environment Agency (England and Wales), United Kingdom quo data, Germany (Subcontractor) Observers from: Norway, Italy, Finland, Sweden and Hungary 23.11..2001

Objectives of the project Development of proposals for: algorithm for data aggregation and assessment of groundwater chemical status algorithm for assessment of trends and trend reversal length of time series and starting point for trend calculations treatment of <LOQ values 23.11..2001

Groundwater bodies Groundwater bodies DK200 DK100 DK300 UK006 NL005 DE001 ES0409 ES0812 ES0829 FR001 FR202 GR001 PTM5 DK200 DK100 DK300 PTA2 PTM2 23.11..2001

Side Products summary of current practice in Member States GW-body characterisation based on provisions in WFD, Annex II web-based form for data collection land use description based on Corine Landcover data GIS maps of GW-bodies development of data exchange formats (quality data and GW-body description) development of databases 23.11..2001

Chemical status (A. V, 2.4.5) Interpretation and presentation of groundwater chemical status (Annex V, 2.4.5) In assessing status, the results of individual monitoring points within a groundwater body shall be aggregated for the body as a whole. ... for those chemical parameters for which environmental quality standards have been set in Community legislation the mean values of the results of monitoring at each point in the groundwater body or group of bodies shall be calculated; and in accordance with Art. 17 these mean values shall be used to demonstrate compliance with good groundwater chemical status 23.11..2001

Need for aggregated data surveillance monitoring identification of risk failing to meet objectives in Art. 4 operational monitoring status assessment trend assessment trend calculations are carried out based on mean values starting point 23.11..2001

Data aggregation Requirements on algorithm: statistically correct development of a pragmatic way one data aggregation method (suitable for small, large and groups of GW-bodies) applicability for all types of parameters 23.11..2001

Data aggregation Candidate methods tested in the project Temporal aggregation (within year and station) Spatial aggregation (over all stations in GW body) by one of the following candidate methods median (empirical) 70% percentile arithmetic mean upper confidence limit of the arithmetic mean kriging mean upper confidence limit of the kriging mean maximum likelihood mean maximum likelihood 70 percentile 23.11..2001

Data aggregation Proposal for general procedure (1) Check whether the GW body consists of several sub bodies with different sampling site densities If no, examine the monitoring network with regard to the network criteria If yes, examine the monitoring networks within subbodies with regard to the network criteria If the network criteria for the monitoring network(s) is not fulfilled, the monitoring network has to be adapted accordingly. For hydrogeologically inhomogeneous gw-bodies: representative network with regard to hedrogeology 23.11..2001

Sampling site distribution 23.11..2001

Data aggregation Proposal for general procedure (2) Use AM or the weighted AM (in case of several subbodies) to estimate the spatial mean (pragmatic approach). If the action limit is exceeded by CLAM, one may use CLKM alternatively (which can be considerably smaller in case of spatial correlation and high variability of the concentration level) 23.11..2001

Trend assessment (A. V, 2.4.4) Identification of trends in pollutants long-term anthropogenically induced upward trends and trend reversal base year or period from which trend identification is to be calculated calculation of trends for a body or group of bodies of groundwater statistical demonstration of trend reversal and level of confidence 23.11..2001

Trend assessment Requirements on algorithm for the selection of the methods the following criteria were taken into consideration: applicability for all types of parameters extensibility to assess and incorporate cause - effect relationship sufficient power for the detection of trend/reversal robustness was considered less important than power and extensibility (data validation will be responsibility of MS) development of a pragmatic way proposal for starting point and length of time series 23.11..2001

Trend assessment Criterion: Power to detect an increase of 30% should be close to 90% (probability to detect a trend) Preliminary conclusion: Method to be applied: Loess smoother Starting point: CL95=75% of action (limit) value 23.11..2001

Trend assessment -starting point 23.11..2001

Trend analysis Minimum length of time series for the detection of an upward trend Annual data: Length >= 8 years and >= 8 values Half-yearly data: Length >= 5 years and >=10 values Quarterly data: Length >= 5 years and >=15 values 23.11..2001

Analysis of a trend reversal Preliminary conclusion: Method to be applied: Two-sections model Minimum length of time series Annual data: Length >= 14 years and >= 14 values Half-yearly data: Length >= 10 years and >=18 values Quarterly data: Length >= 10 years and >=30 values 23.11..2001

Trend reversal 23.11..2001

Links to other Working Groups monitoring network design (e.g density) analytical requirements for LOQ and LOD monitoring frequency guidance for delimitation of GW-bodies data exchange format (GW-body description, quality data) characterisation of GW-bodies identification of risk presentation of results groundwater action values ..... 23.11..2001

23.11..2001

Results and products algorithm for data aggregation, trend and trend reversal assessment software tool available for free summary report website including all information elaborated within the project web-GIS-presentation of results 23.11..2001