To assess trends in water quality, the TransNational Monitoring Network (TNMN) carefully monitors physical, chemical and biological conditions in the Danube and its major tributaries since 1996. The TNMN for the Danube builds on national surface water monitoring networks, and consists of 79 monitoring stations.
Facts and Figures
As the Danube flows towards the Black Sea conditions in its waters change considerably. From the upper to the lower reaches of the Danube scientists have monitored significant overall increases in the following determinands:
- suspended solids
- organic pollution (expressed by COD)
- organochlorine pesticides (Lindane, DDT)
- concentrations of heavy metals (especially cadmium, and with the exception of manganese, for which the maxima were observed in the middle Danube)
- concentrations of nitrite and ammonium (however, the concentration of nitrate decreases)
- phosphorus (both total phosphorus, and phosphate)
- conductivity (caused by dissolved salts)
Most tributaries contain higher concentrations of organic pollutants and nutrients than the Danube itself.
However the TNMN Yearbook 2001 clearly pointed out positive changes in the water quality in 2001 compared to the comparative assessment 1996-2000:
- Reductions in biodegradable organic pollution were visible in the Austrian and Slovakian stretches of the Danube, at Danube-Hercegszanto, and in the lower reaches of the river downstream of Danube Chiciu/Silistra.
- Less biodegradable organic pollution was also observed in tributaries including the Inn, Dyje, Drava, Arges and Siret.
- Ammonium concentrations had decreased in the upper part of the Danube all the way down to Danube Szob, and in the tributaries from the upper reaches down to the River Vah.
- Reductions in nitrate loads were observed at several stations in the German and Austrian parts of the river basin; at Danube-Szob; in the tributaries Morava, Dyje, Vah, Drava; and at Sava–us.Una Jasenovac.
- Phosphate concentrations had generally decreased along the joint Slovak–Hungarian section of the Danube, and in tributaries entering the upper Danube, as well as at Drava, at Siret, and at stations located on the River Sava at Sava–us.Una Jasenovac.
IAWD Good drinking water quality
The Danube is a drinking water source in many locations. According to an IAWD study programme conducted in 2001 and 2002 good water quality for drinking water purposes (without treatment) has only been achieved in the stretch of the Danube between Dettingen and Leipheim (Germany) and Mohacs (Hungary). However, oxygen levels of the Danube are high enough to allow treatment with natural processes, such as bank-filtering or slow sand filtration to reach drinking water quality.
Additional technical measures to maintain the drinking water standards are only necessary during extreme events including floods, incidents involving hazardous substances and insufficient wastewater purification.
The key purpose of Joint Danube Surveys (JDS) is to produce reliable and comparable information on carefully selected elements of water quality for the length of the Danube River, including its major tributaries. Three Joint Danube Surveys have previously been conducted, in 2001, 2007, and 2013. The fourth of its kind, JDS4 was launhed in June 2019 at sampling sites in 13 countries across the Danube River Basin.
The investigation of the Tisza River was a follow-up project of the Joint Danube Survey 2001 organised by the ICPDR. The objective of the survey was to investigate the water quality along the river and to promote public awareness. The countries participating at the survey include Romania, Slovakia, Hungary, and Serbia and Montenegro.
Through the TransNational Monitoring Network (TNMN), the contracting parties of the ICPDR monitor water quality pollution and long-term trends in water quality and pollution loads in the major rivers in the Danube River Basin. The collected data is published annually in the “TNMN Yearbooks”, which you can download here.
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