Adapting the CUAHSI Hydrologic Information System to OGC standards

The CUAHSI Hydrologic Information System (HIS) provides web and desktop client access to hydrologic observations via water data web services using an XML schema called “WaterML”. The WaterML 1.x specification and the corresponding Water Data Services have been the backbone of the HIS service-oriented architecture (SOA) and have been adopted for serving hydrologic data by several federal agencies and many academic groups. The central discovery service, HIS Central, is based on an metadata catalog that references 4.7 billion observations, organized as 23 million data series from 1.5 million sites from 51 organizations. Observations data are published using HydroServer nodes that have been deployed at 18 organizations. Usage of HIS has increased by 8x from 2008 to 2010, and doubled in usage from 1600 data series a day in 2009 to 3600 data series a day in the first half of 2010. The HIS central metadata catalog currently harvests information from 56 Water Data Services. We collaborate on the catalog updates with two federal partners, USGS and US EPA: their data series are periodically reloaded into the HIS metadata catalog. We are pursuing two main development directions in the HIS project: Cloud-based computing, and further compliance with Open Geospatial Consortium (OGC) standards. The goal of moving to cloud-computing is to provide a scalable collaborative system with a simpler deployment and less dependence of hardware maintenance and staff. This move requires re-architecting the information models underlying the metadata catalog, and Water Data Services to be independent of the underlying relational database model, allowing for implementation on both relational databases, and cloud-based processing systems. Cloud-based HIS central resources can be managed collaboratively; partners share responsibility for their metadata by publishing data series information into the centralized catalog. Publishing data series will use REST-based service interfaces, like OData, as the basis for ingesting data series information into a cloud-hosted catalog. The future HIS services involve providing information via OGC Standards that will allow for observational data access from commercial GIS applications. Use of standards will allow for tools to access observational data from other projects using standards, such as the Ocean Observatories Initiative, and for tools from such projects to be integrated into the HIS toolset. With international collaborators, we have been developing a water information exchange language called “WaterML 2.0” which will be used to deliver observations data over OGC Sensor Observation Services (SOS). A software stack of OGC standard services will provide access to HIS information. In addition to SOS, Web Mapping and Feature Services (WMS, and WFS) will provide access to location information. Catalog Services for the Web (CSW) will provide a catalog for water information that is both centralized, and distributed. We intend the OGC standards supplement the existing HIS service interfaces, rather than replace the present service interfaces. The ultimate goal of this development is expand access to hydrologic observations data, and create an environment where these data can be seamlessly integrated with standards-compliant data resources.