GIS-based water safety planning in the catchment area of abstraction wells | GIS-basierte Wassersicherheitsplanung im Einzugsgebiet von Trinkwasserbrunnen

In the fight against water-borne diseases and epidemics, international preventive management methods to ensure safe drinking water supplies have become more important in recent decades. The WHO’s Water Safety Plan (WSP) presents a process-oriented concept to avoid preventable threats to safe supplies (quantity and quality) from the source to the consumer. This concept includes selective testing of the water quality (product quality) as well as the quality of the structures and processes. Particularly in abstraction areas, certain risks like e.g. flooding or increasing competition for land use can affect the water supply.This case study demonstrates that especially in catchment areas, geographic information systems (GIS) offer a valuable tool for implementing many aspects of the WSP.In this context, it is important to differentiate between isolated, linear and broad-spread threats, and to create an individual layer or feature class for each category (e.g. road networks, land use, flooding etc.). Pursuing a semi-quantitative approach proved to offer a suitable method for evaluating potential risks. Though lack of available data made it necessary to modify conventional semi-quantitative risk assessment methods, excellent results were achieved, providing an approximate and informative overview of the main risks in the catchment area.This study addresses only a small part of the WSP, but nevertheless shows the extent to which the process before the water from the catchment (resource) makes its way to the actual abstraction points needs to be understood. GIS can be used to visualize, layer and combine possible risks and process-related information. On the basis of the results, it was possible to create risk maps, and to visualize, assess and prioritize various potential threats.