The Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI) has been established to promote research infrastructure that advances Hydrologic Sciences. Hydrologic Information Systems (HIS) are part of this infrastructure. Hydrologic information is collected by many individuals and organizations in government and academia for many purposes, including general monitoring of the condition of the water environment and specific investigations of hydrologic processes and environments. This paper describes HIS capability developed to promote data sharing and interoperability in the Hydrologic Sciences with the ultimate goal of enabling hydrologic analyses that integrate data from multiple sources. The CUAHSI HIS is an internet based system to support the sharing of hydrologic data. It is comprised of hydrologic databases and servers connected through web services as well as software for data publication, discovery and access. The system that has been developed provides new opportunities for the water research community to approach the management, publication, and analysis of their data systematically. The system’s flexibility in storing and enabling public access to similarly formatted data and metadata has created a community data resource from public and academic data that might otherwise have been confined to the private files of agencies or individual investigators. HIS provides an analysis environment for the integration of data from multiple sources and serves as a prototype for the infrastructure to support a network of large scale environmental observatories or research watersheds.