Good water quality maintains biodiversity of aquatic and terrestrial species and guarantees health and wealth of human beings. The quality of surface waters and groundwater is also continuously under pressure, given physical modifications and point and diffuse pollution by various sources (e.g. UNESCO 2012). Addressing poor water quality is thus a major sustainable development goal (SDG), as pointed out with SDG 6.3. on improving the quality of waters (e.g. UN Water 2015). Addressing water quality issues is, however, not an easy undertaking. In order to address water quality issues, correct water quality monitoring and reporting based on indicators and indices is important. Indicators refer here to single parameters to measure water quality (e.g., phosphorus, pH, temperature, turbidity), whereas indices relate to combinations of indicators (e.g., WATQI which includes dissolved oxygen, electrical conductivity, pH, total nitrogen and total phosphorus). Water quality-related research has provided a large set of useful, but often context-specific, indicators and indices (e.g. Fernández et al. 2004, UNEP 2014, Srebotnjaket al. 2012). Such indicators and indices are applied at the global level with reference to the SDGs. Moreover, indicators and indices are adapted and modified to fit a specific setting (e.g., depending on national goals).
Whereas there is a large set of indicators and indices, there is a lack of systematic overviews of water quality indicators and indices and of their application in practice. Most importantly, the research community has to identify challenges in the application of water quality indicators and indices. First, in terms of quantity, we are unaware of the actual number of water quality indicators in national guidelines and indices. Second, and in terms of quality, criteria for prioritizing case specific water quality indicators are to be identified. The project ‘Understanding Water Quality Indicators and Their Application’ aims to address these quantitative and qualitative challenges, based on an analysis of documents and surveys among water quality experts. Results of this project will help researchers to identify relevant research questions related to the issue of water quality indicators and indices. Moreover, the results will help scientists and practitioners in designing relevant capacity development programs for measuring water quality in the future. This, again, improves indicator based assessments, monitoring and improvements of water resources, ultimately facilitating the achievement of the SDGs.