OpenHiGis: A national geographic database for inland waters of Greece based on the INSPIRE Directive Hydrology Theme

The Open Hydrosystem Information Network (OpenHi.net) is an information infrastructure for the collection, management and dissemination of hydrologic information related to inland waters in Greece. The OpenHi.net is under development in the context of HIMIOFoTS, a national infrastructure integrating both marine and inland waters. OpenHi.net is mainly oriented to collect and manage river and lake stage data. Geographic data are essential to link stage data with the upstream basin’s hydrologic characteristics. The OpenHiGis is the GIS component of the OpenHi.net platform. The geographic database design and implementation are based on the Hydrography Theme specified by the INSPIRE Directive. The main goal is to collect, query, analyze, and offer web services relevant to hydrologic - geographic information for hydrographic network, lakes and reservoirs, river basins, drainage basins and station basins at a national level. In this sense, data stored for (a) hydrographic network (geometry, length, segment’s slope, geographical name and stream order), (b) lakes and reservoirs (geometry, area, elevation and geographical name) , and (c) basins (geometry, area, elevation, slope, basin order, main watercourse length and slope, runoff Curve Number.

The European Digital Elevation Model (Copernicus, EU-DEM version 1.1) with spatial resolution of 25 m, is selected (after examining a few well-known elevation models) for extracting hypsometric information, which is basic for river basin’s response. Other main data sources found and used are the: (a) hydrographic network, lakes and reservoirs from the implementation of EU 2000/60/EC Directive, (b) hydrographic network from EU 2007/60/EC Directive and (c) OpenStreetMap publically available hydrographic network and river networks from various scanned maps at scales approximately 1:50 k.

The ArcGIS Model Builder environment is used as the main spatial analysis tool. Several models are created to run the geographic processes and perform calculations (create INSPIRE compliant geodatabase, data import from various sources, watercourse extraction from DEM and hydrographic network definition, river basins delineation and geomorphologic attributes calculation, watercourse naming, topology creation and validation). The extraction of a primary (before editing) watercourse line is achieved by using the EU-DEM, applying  an upslope contribution area threshold equal to 10 km², which is proposed by the EU 2000/60/EC Directive. Spatial relationships between features are defined using topological rules. All the modeling procedures and the output datasets are considered to be at a scale 1:50 k.

The QGIS software is used to perform the final editing by using OSM’s, ESRI’s, Google’s and Bing’s base-maps. Furthermore, QGIS is used to make a connection to the ArcGIS geodatabase and transfer the data to PostGIS (Postgres). Finally, the MapServer software is used for publishing the data to the web. Two services, the Web Map Service (WMS) and the Web Feature Service (WFS), are provided to the user to access, query or download the geographic data through the OpenHi.net platform.