Why not all water quality is the same
Life needs water. With its more than 800 water management facilities and around 1,000 employees, the Ruhrverband ensures that people in the region have access to sufficient quantities of good quality water at all times.
But how is water quality actually measured? Generally speaking, it is the composition of the substances contained in the water. However, the criteria and characteristics used to assess water quality vary greatly depending on whether it is drinking water or process water, whether the results of wastewater treatment, the condition of bathing water or the overall ecology of the water body are being considered.
In the water sector in particular, the topic of water quality has become very important, especially as a result of the European Water Framework Directive. The ecological status of a body of water is divided into five categories (very good, good, moderate, unsatisfactory and poor) and assessed on the basis of biological and physico-chemical characteristics. The communities of aquatic invertebrates, fish and aquatic plants are used to assess the ecology of water bodies.
In the case of bathing waters, water quality is primarily assessed on the basis of hygienic parameters (e.g. Escherichia coli). According to the European bathing water report, the bathing areas designated at the Ruhrverband reservoirs have excellent or good bathing water quality. Swimming in the Ruhr has also been possible again since 2017. The cities of Essen, Bochum and Mülheim have now put an official bathing area into operation.
Wastewater is discharged into bodies of water after being treated. To protect water bodies, the treated wastewater should have as little impact as possible on water quality and aquatic biology. For this reason, the discharges and the downstream waters are analysed chemically, physically and biologically. In particular, trace substances contained in wastewater are increasingly becoming the focus of interest due to improved analytical methods.
In the case of drinking water, it is particularly important to ensure that it is hygienically safe and contains as few harmful trace substances as possible, such as heavy metals and pesticides.
Structure of the water bodies in the Ruhr catchment area
In addition to the quality of the flowing water, the hydromorphological condition of the water body also has a significant influence on the composition of flora and fauna.
The bed, banks and surroundings of a watercourse are the habitat of animals and plants and the way they are characterised influences their diversity and quantity. In order to assess these various structural elements of a watercourse, the Länderarbeitsgemeinschaft Wasser has developed a procedure in which information on the course development, the longitudinal and transverse profile, the condition of the bed and the design and utilisation of the banks and watercourse environment is collected for sections of watercourse defined by length.
The water body structures surveyed are categorised into seven classes, similar to the water quality. These range from unchanged condition (class 1) to a completely altered water body structure (class 7). The results are generally presented in the form of five watercourse-parallel bands, which reflect the conditions found for the bed, the right and left banks and the watercourse environment.
Between 2011 and 2013, the State Agency for Nature, Environment and Consumer Protection of North Rhine-Westphalia collected information on the structure of watercourses throughout the state for the last time. According to this, the following percentage distribution of the seven structural classes is available for the 1,850 km of water bodies subject to reporting in the Ruhre catchment area in accordance with the European Water Framework Directive (in the presentation form aggregated to one band).
Water quality in the Ruhr catchment area
Since 2007, the water status in the Ruhr catchment area has been presented in the form of ecological water status maps as part of the Ruhrverband's cooperative involvement in operational water monitoring in accordance with the European Water Framework Directive (EC WFD).
The data sources used are the survey results from the water body monitoring carried out jointly by the Ruhrverband and LANUV NRW. Data collected by the Ruhrverband as part of the "Integral Drainage Planning" (IEP) is also taken into account. Macrozoobenthos is one component used to describe the condition of water bodies. This community of insects, whirlworms, crustaceans, worms, leeches, mussels and snails living in flowing water or on the river bed reflects the ecological quality, or ecological status, of a section of water under consideration.
Water condition - Saprobic
Ecological water body status in the Ruhre catchment area - macrozoobenthos (saprobic module), 2015-2020. Around 97 per cent of the sampling sites have a "good" or "very good" saprobic status, i.e. low to very low organic pollution.
Water body status - General degradation
Ecological water body status in the Ruhre catchment area - macrozoobenthos (general degradation module), 2015-2020. Around 49 per cent of all sampling sites examined show a "good" or "very good" status in terms of general degradation. The reasons for the "moderate", "unsatisfactory" and, in individual cases, "poor" status at the remaining sampling sites are often the utilisation-related changes in watercourse structures.
More information on the water quality of the Ruhr can be found in the current Ruhr Quality Report.