Box 5E Data and information sources

Information in this section is based on:

Four different questionnaires were used. Two were designed to provide general information about the rivers and lakes in each country, while the other two were designed to provide more specific information about 10 to 20 rivers and lakes in each country. In addition, time-series data for rivers were obtained from the EU according to Council Decision (77/795/EEC), the UNEP/GEMS database (in Burlington, Canada), the INFODANUBE database (Regional Environmental Centre for Central and Eastern Europe, in Budapest, Hungary), and from a supplementary questionnaire sent to countries outside the EU. The questionnaires were used as a tool to ensure that comparable information was obtained on the various environmental problems in the different countries. Many persons in many countries have made a great effort to answer the questionnaires. A total of 28 countries, especially Eastern European, Nordic, and EFTA countries, were kind enough to answer the questionnaires (Table 5.7). However, the information supplied differed greatly; some countries provided only sparse information about a few waterbodies, while others supplied information from national surveys that included more than 500 or 1000 rivers or lakes. When a response to the questionnaires was lacking or incomplete, national or regional environmental reports were reviewed and analysed to ensure geographical coverage as wide as possible. In these cases the country information shown on maps in this chapter may not always accurately represent the actual situation.

Major additional sources of information were as follows: Austria: Wasserwirtschaftkataster, 1992; the Belgian Flanders: Vlaamse Milieumaatschappij, 1992; Estonia: Milius, 1991; 116 large rivers in the EU countries: Council Decision (77/795/EEC); Ireland: Flanagan and Larkin, 1992; Italy: Istituto di Ricerca sulle Acque 1990, Gaggino et al, 1987; Northern Ireland: Gibson, 1986, 1988; Norway: NIVA, 1990a,b; Portugal (river Douro and tributaries): DGQA, 1991; Spain: Dirección General de Obras Hidráulicas del MOPU, 1989; the UK: Institute of Hydrology and British Geological Survey, 1990 and UK DoE, 1992; West Germany: Umweltbundesamt, 1992. The very small European countries are only briefly considered.

In all, information has been collected from 800 river stations in more than 550 European rivers, as well as from more than 1500 lakes. Information was obtained about the largest rivers in nearly all countries (Table 5.9), this being supplemented by data from numerous smaller rivers for which land usage and human activity in the catchment area are known. Descriptive statistics for frequently measured physical and chemical variables in European rivers are given in Table 5.8. Information provided about the general environmental state of European lakes was less extensive, only 18 countries having completed the general lake questionnaire; this information was therefore supplemented with data from national lake surveys, as well as information from the scientific literature.

The European countries dealt with in this section have been divided into four regions: Nordic, Eastern, Western, and Southern (Figure 5.3).

The results on chemical concentrations in this section are generally based on annual mean values (rivers) or summer mean values (lakes) from the period 1988­91. Several results are presented as summary statistics for a group of rivers or lakes by means of frequency distributions (pie-charts) and box-cox diagrams. The frequency distribution for organic matter and nutrients in rivers and lakes (maps with pie-charts) are based on information supplied by each country on the percentage of rivers or lakes having organic matter or nutrient levels within specified classes, for example, the percentage of rivers with annual mean phosphorus levels below 25 µg P/l, between 25­50 µg P/l, 50­125 µg P/l, and so on.

The box-cox diagrams that illustrate, for instance, the relationship between total phosphorus and population density in river catchments (eg, Figure 5.8) have been compiled by grouping the rivers in population density classes, for example, 30 rivers with fewer than 15 inhabitants per km2 and 19 rivers with more than 100 inhabitants per km2. The median value (the middle bar), the upper and lower quartiles (the upper and lower box), and the 10 and 90 per cent percentiles (the bar at the end of the lower and upper lines) have been calculated for each class. In rivers with a catchment population density exceeding 100 inhabitants per km2, 50 per cent of the rivers have annual mean total phosphorus levels above and below 300 µg P/l, and 75 and 25 per cent of the rivers have phosphorus levels above and below approximately 100 µg P/l respectively (lower quartile).


Table 5.7 - Countries that have answered the river and lake questionnaires

CountryRivers Lakes
Form IForm II Form IForm II
Albania X 5 ­ (3)
Austria (X) 4 (X) ­
Bulgaria X 10 (X) 5
Croatia X 26 ­ 4
Czech Republic X 15 ­ ­
Denmark X 70 X 37
Estonia ­ 12 X 3
Finland X 21 X 19
France X ­ ­ ­
Georgia X 14 (X) 6
Hungary X 4 ­ 3
Iceland X 2 X 1
Latvia X 15 X ­
Lithuania X 15 ­ ­
Luxembourg X ­ X ­
Moldova X 7 X 9
The Netherlands X 3 X 7
Norway X 19 (X) 12
Poland X 19 X 16
Romania X 26 ­ 16
Russian Federation X 16 ­ 4
Slovenia X 21 ­ ­
Spain X 3 (X) 7
Sweden X 21 X 9
Switzerland X 4 X 9
Turkey ­ ­ X ­
UK X ­ X ­
Ukraine ­ 37 ­ 6

Note: Form I is a general questionnaire and Form II gives information about specific rivers and lakes. The number of questionnaires with information about specific rivers and lakes is listed. X forms completed; (X) only sparse information; ­ no form information.


Table 5.8 - Descriptive statistics of annual mean physical and chemical variables at European river stations

 Number of
river stations
Percentage of
river stations
with concentrations
not exceeding
 25% 50% 75%
pH 717 7.5 7.8 8.0
Total alkalinity (meq/l) 274 1.0 2.5 4.0
Chloride (mg Cl/l) 442 17.3 26.5 68.3
Organic matter and oxygen level (mg O2/l)
Biochemical oxygen demand 645 1.9 2.8 4.7
Chemical oxygen demand 470 7.8 15.0 25.0
Dissolved oxygen 620 8.4 9.7 10.7
Nitrogen (mg N/l)
Ammonium 580 0.1 0.2 0.4
Nitrate 654 0.7 1.8 3.9
Total nitrogen 329 0.8 2.1 4.5
Phosphorus (µg P/l)
Dissolved orthophosphate 412 45.0 124.0 286.0
Total phosphorus 546 59.0 170.0 366.0
Heavy metal (µg/l)
Copper 192 1.0 4.0 8.0
Zinc 176 5.0 10.0  

Note: The following example for dissolved orthophosphate shows how to read the table. For this compound annual mean concentrations have been gathered for 412 European river stations. Of these, 25 per cent (103 stations) had concentrations below 45 mg P/l; 50 per cent (206 stations) were below 124 mg P/l and 75 per cent (309 stations) were below 286 mg P/l, respectively.