[VD04] Quality of watercourses
Key message
For the period 2002–2005, an improvement in the chemical and saprobiological quality of rivers was observed.
Due to changes in legislation, this indicator was replaced in 2006 by the indicator [VD12] Chemical and ecological status of surface Waters.
Definition
The quality of watercourses is presented in two ways: as a chemical status in accordance with the Decree on the chemical status of surface waters and as a saprobiological index according to a method developed by Pantle and Buck and later modified by Zelinka and Marvan.
The chemical status of watercourses is established in relation to limit values of parameters specified by the Decree on the chemical status of surface waters (Official Gazette of the Republic of Slovenia, No. 11/2002), which transposes articles 7 and 8 and Annexes V, VIII and IX of Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy (hereinafter: Directive 2000/60/EC). Chemical status is established on the basis of annual average value of parameters for which limit values are defined in the above-mentioned directive. Based on the calculated annual average value of individual parameters and a time series of annual average values of parameters from the priority list of substances to be determined in sediment, and taking into account the hydrological conditions at the time of individual samplings, chemical status (good or bad) is determined for each individual measuring site for a certain year.
The methodology for assessing the ecological status of surface watercourses in accordance with Directive 2000/60/EC is not fully developed yet. Accordingly, biological assessment of the quality of surface watercourses in Slovenia for the period 1996–2005 was carried out using the same methodology of past years (Pantle-Buck method modified by Zelinka and Marvan). Saprobic procedures are based on the calculation of values of the saprobic index of a biocenosis. A watercourse at a measuring site is ranked in a quality class corresponding with its index value. Four basic and three intermediate classes exist. They are ranged from quality class one (best) to four (worst) according to the quality of the living environment in watercourses.
In 2005, quantitative sampling of macrozoobenthos and periphyton using the multi-microhabitat sampling method (Urbančič et al., 2005a, Kosi et al., 2005) was carried out for the first time at some measuring sites in Slovenia. The obtained samples were analysed in laboratories in terms of the counting of organisms as well as the required rate of determination according to new methodology (Urbančič et al., 2005b, Kosi et al., 2005). Merging of the obtained results into a system, on the basis of which ecological status will be assessed in accordance with the requirements of Directive 2000/60/EC, is planned to be concluded in 2007 as in many other EU countries.
Charts
Standardised Database for Water Quality Monitoring, Slovenian Environment Agency, 2006
| 2002 | 2003 | 2004 | 2005 | ||
|---|---|---|---|---|---|
| good chemical status | number | 71 | 71 | 75 | 73 |
| good chemical status | % | 75 | 80 | 84 | 83 |
| bad chemical status | number | 24 | 18 | 14 | 15 |
| bad chemical status | % | 25 | 20 | 16 | 17 |
Standardised Database for Water Quality Monitoring, Slovenian Environment Agency, 2006
| 1996 | 1997 | 1998 | 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|
| class I. | % | 6.6 | 3.3 | 3.2 | 4.2 | 3.7 | 5.3 | 4.3 | 7.7 | 8.5 | 11.8 |
| class I.-II. | % | 23.1 | 28.6 | 34.7 | 33.7 | 34.6 | 28.7 | 28.3 | 26.2 | 31 | 32.4 |
| class II. | % | 58.2 | 51.6 | 52.6 | 49.5 | 48.6 | 54.3 | 58.7 | 53.8 | 50.7 | 54.4 |
| class II.-III. | % | 9.9 | 13.2 | 5.3 | 9.5 | 8.4 | 5.3 | 3.3 | 7.7 | 7 | 0 |
| class III. | % | 2.2 | 3.3 | 4.2 | 3.2 | 4.7 | 6.4 | 5.4 | 4.6 | 1.4 | 1.5 |
| class III.-IV. | % | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1.4 | 0 |
| class IV. | % | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Goals
- To achieve good water status by 2015.
- To preserve the quality of water, enabling watercourses to support important freshwater fish species.
Comment
The quality of watercourses in Slovenia is improving.
A trend toward improvement of the chemical status of surface watercourses was observed in the period 2002–2005. The number of measuring sites where monitoring of chemical status of surface watercourses was carried out was constantly changing throughout the above-mentioned period. In 2002, 95 measuring sites were included in monitoring, while in 2003 and 2004, the number of stations was 89. In 2005, monitoring of chemical status of surface watercourses was carried out at 88 measuring sites. Compared to 2002, the share of measuring sites with good recorded chemical statuses of water increased in 2005. During the period 2002–2005, the share of measuring sites with bad recorded chemical status of water increased constantly. The trend of a slight decrease in water quality was observed in 2005, which can be contributed to a smaller number of measuring sites compared to preceding years.
The trend of improving saprobiotic quality of watercourses was also observed. The number of measuring sites in quality classes 1 and 2 increased, while the number of sites in lower quality classes decreased. An assessment of the saprobiological status of surface watercourses in the period 1996–2005 shows that the highest water quality was recorded in 2005. The share of measuring sites that were ranked in quality classes 1, 1-2 and 2 was 87.9% in 1996 and 98.6% in 2005. The number of measuring sites where monitoring of saprobiological quality of surface watercourses was carried out was constantly changing throughout the period 1996–2005. In the period 1996–2002, water samples were examined at 91–107 measuring sites, while in the period 2003–2005, water samples were examined at 65–71 sites. The number of measuring sites was reduced due to the requirements of Directive 2000/60/EC, according to which measuring sites are divided into basic, referential and additional sites.