Technical report. Organization of geographical data

Open Hydrosystem Information Network (OpenHi.net) is a large-scale surface-water monitoring infrastructure for Greece, providing free access to water data and incorporating existing networks that manage their own databases. OpenΗiGis is the GIS component of the system, helping in linking stream flow to hydrological characteristics of upstream basins. The main goal is to collect, query and analyse data, to offer web-services related to hydrological-geographical information for watercourses and hydrographic networks, lakes and reservoirs, stream drainage basins and basins upstream of monitoring stations at the national level. Stored watercourses attributes are segment length and slope, geographical name and stream order. Attributes stored for lakes and reservoirs are area, elevation and geographical name. Attributes stored for basins (river basins, drainage basins, monitoring stations upstream basins) are area, mean elevation, mean slope, basin order, main watercourse length and slope, mean curve number. Spatial relationships between features (watercourses, basins, nodes) are defined using relevant and validated topological rules. A toolbox with several models was created to perform the geographical processes and to run calculations of spatial and geomorphological attributes. Such models, for example, are: watercourse extraction, hydrographic network definition, river basin delineation, geodatabase creation, data import from various sources and data export to the geodabase, a naming model to give name to each segment, basin’s mean curve number calculation. Web Map Services (WMS) and Web Feature Services (WFS) are provided to access, query and download the data through the OpenHi.net platform.