A GIS TOOL FOR THE FAST IDENTIFICATION OF DRINKING WATER ABSTRACTION POINTS POSSIBLY REACHED BY A CONTAMINATION EVENT

In the framework of a collaboration between the Water Research Institute and the National Civil Protection Department, in order to improve response capability at both national and local level, a procedure for the emergency management of accidental pollution of groundwaters is being developed. When an accidental spill happens, due for example to the overturning of a tank lorry, a key aspect is often not only the scarce information available, but the ability to manage it optimally to obtain quick responses, hence support decision making. In the first part of the procedure, a GIS tool allows for the fast identification of the drinking water abstraction points possibly involved by the contamination. Additionally the tool can facilitate the management of the available geographical data for further modelling and analysis of the site. The tool is thought to be used also by non-expert personnel. The aim of this poster is to describe the conceptual model of the tool. A brief description is here summarised. When launching the tool the user is asked to place the contamination event location on a GIS by its coordinates. The main information regarding the event (name, description, date, operator, contaminant, etc.) can be stored in a report. Other relevant information (e.g. administrative data, lithology and hydrological complex in which the event falls) is obtained automatically by means of the GIS overlay techniques (spatial queries) and stored in the report. Then, the drinking water abstraction points which are located within a circular area (buffer) around the spill are identified. The buffer is designated around the event, whose radius increases with the permeability of the hydrogeological complex in which the event falls (generally 1-3 km, up to 15 km for karstified limestones). As data on drinking water points should come from different local databases, an archive that integrates various sources was built. This archive is essentially a summary table containing the spatial coordinates of each water point and a link to their parent databases. Finally the tool automatically selects and loads in the project the available layers (previously stored in databases) that insist on the event area to be used for a further characterization of the event. For example, a first estimation of the parameters to be used in transport models could be derived from the relevant layers (e.g. geological-hydrogeological maps, vulnerability maps, etc.). The tool was implemented using ArcGIS and Python scripting language. In the emergency management of groundwater pollution events, the aim of this application is to facilitate the pre-alert phase and successively the consultation of the available layers to support the analysis.