An object-oriented hydrogeological data model for groundwater projects.

Geological and hydrogeological data are expensive to obtain in the field but are crucial for specific hydrogeological studies, from hydrogeological water balances to groundwater flow modelling and contaminant transport, or for more integrated environmental investigations where groundwater plays a role. In this context, hydrogeological data are collected, transformed and exchanged at different scales, from local to international levels and between numerous institutions ranging from environmental consulting companies to the national and international environmental administrations. To guarantee that these exchanges are possible and meaningful, a clear structure and meta-information on applied hydrogeological data models is required. To make one step towards seamless management of groundwater projects, a new hydrogeological data model has been developed: H^g"2O. It is described using object-oriented paradigms and it follows the recommendations of the International Organization for Standardization (ISO/TC211), the Open Geospatial Consortium (OGC), and the European Geospatial Information Working Group. Hydrogeological features are organized in packages of spatial feature datasets. The observations and measurements related to these features are organized in a separate package. A particular focus is on specialized hydrogeological field experiments such as hydraulic and tracer tests. Two first implementations in the proprietary desktop ArcGIS environment and in the open source web-based Web2GIS platform are presented, focussing on their respective standards support.