- The recommended overall objective of the monitoring (information) network is: "To obtain timely, quantitative and comparable information on the status of inland waters (groundwater, lakes/reservoirs, rivers and estuaries) from all EEA Member States so that valid temporal and spatial comparisons can be made, and so that key environmental problems associated with Europes inland waters can be defined, quantified and monitored".
- The favoured option for the basis of the monitoring network is to sub-sample a representative portion of the total water resources. This would be aided by stratifying the total population (e.g. all rivers) into relativity homogenous sub-strata.
- It is recommended that the sampling stations to be included into the EEA network should be selected from the sampling stations in national monitoring programmes supplemented by additional stations to meet specific requirements of the EEA. In cases where no national monitoring programmes exist, the stations to be included will, if possible, be selected from regional sampling stations.
- The network should be a representative sub-sample of the inland water bodies of the EEA area and the sampling stations to be included in the network should be selected so that they are representative of:
- the size/numbers/types of water bodies in the EEA area (e.g. lake surface area);
- the variation in human pressures (e.g. population density and land use);
- and should include a number of reference and flux stations.
- A representative stratified monitoring network has been recommended with stations stratified according to the type and size of water body, catchment characteristics and human activities. Each additional stratum added to the design would increase the need for supportive information by which the target population in the strata can be defined, and for definitions such as what population density represents an urbanised catchment, what proportion of agricultural use a predominately agricultural catchment, the predominant agricultural use, a forested catchment. These definitions would require the assistance of other EEA Topic Centres and may require revision in the light of experience with the network.
- It is recommended that the optimum monitoring station densities (for example, per country and water type - river, lake or aquifer), sampling frequencies, sample numbers and sampling windows for the proposed networks are defined according to the statistical principles and considerations described in this report. These aspects should be developed during the pilot implementation of the network using non-aggregated monitoring data from a number of countries and water types.
- The possibility of aggregating data and information from representative stations on a regional, catchment or aquifer basis should be investigated in later phases of implementing the networks.
- Initially a general surveillance network for rivers could contain a network of approximately 1832 rivers, made up of 1466 representative and 366 reference rivers, and an impact network consisting of 1,588 rivers selected on the basis of population density. The largest and most important national rivers in the EEA area and existing flux stations would also be included.
- It is recommended that for the pilot implementation of the network that the same selection procedure is applied to the surface quantity network as for the river quality network, and select where possible quality and quantity stations at the same location or at least on the same river reaches. Baseline stations should be selected independently.
- Initially a general surveillance network for lakes/reservoirs would comprise: a basic network containing around 1,000 water bodies, 200 of which would be reference and 800 representative lakes; an impact network containing 800 lakes, (selected on the basis of population density to put more emphasis on water bodies in densely populated areas than in sparsely populated areas); and, the largest and most important national lakes in the EEA area.
- Even though sample station density for the groundwater network should be based on national geological conditions and variability in measured determinants, it is proposed that the selected monitoring stations should initially be distributed in a more or less regular geometric pattern and, as a rule, with a density of at least 1 site per 20 to 25 km2 of aquifer. It will be important to confirm that the monitoring wells, which are chosen for the EEA network, should have been designed and constructed in a same way so it is possible to compare the results from all the Member States.
- It is recommended, at least for the pilot implementation study on rivers, that assessments are made on data obtained over the whole year, spread approximately evenly over that period (e.g. monthly). In addition, long time series (monthly or more frequent) data should be obtained from a range of hydrological river types to assess relatively short term (e.g. monthly, seasonal) and longer term variability (yearly). This would enable a more rational sample frequency to be established and take into account problems such as rivers drying out in summers in some countries.
- In the interim it is recommended that the summary information for lakes be based on a minimum of 8 samples a year.
- For groundwater two samples a year, (one each during high and low ground water levels), should be adequate. When deeper groundwater reservoirs occur at the same sampling station they should be sampled at the same time as the shallower ones.
- It is recommended that the suggested networks are piloted in a few selected countries during the first half of 1996, and subsequently, progressively implemented throughout the EEA area in a planned and programmed way later in 1996 and in subsequent years. For the pilot project, station selection will be undertaken using the proposed criteria and procedures, and non-aggregated data will be needed to test and assess intra- and inter-strata variability, and to investigate optimum sample station densities and sample frequencies. In addition, probably in the second half of 1996 and in subsequent years, analytical and sampling methodology will be examined in detail to identify further potential barriers to harmonisation. Finally, the meta-data transfer process to the Agency will be tested once data dictionaries and formats have been developed and finalised. Support will also be required from other Topic Centres on the catchment and human activity information that will be required. All these activities are scheduled into the work programme of the Agency under the control of the Project and Programme Manager.
For references, please go to www.eea.europa.eu/soer or scan the QR code.
This briefing is part of the EEA's report The European Environment - State and Outlook 2015. The EEA is an official agency of the EU, tasked with providing information on Europe’s environment.
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