Presentation given to CUAHSI Informatics Conference, July 26, 2017.

HydroShare is an online, collaboration system for sharing of hydrologic data, analytical tools, and models. It supports the sharing of and collaboration around “resources” which are defined by standardized content types for data formats and models commonly used in hydrology. With HydroShare you can: Share your data and models with colleagues; Manage who has access to the content that you share; Share, access, visualize and manipulate a broad set of hydrologic data types and models; Use the web services application programming interface (API) to program automated and client access; Publish data and models and obtain a citable digital object identifier (DOI); Aggregate your resources into collections; Discover and access data and models published by others; Use web apps to visualize, analyze and run models on data in HydroShare. HydroShare supports web apps to act on resources for cloud (server) based visualization and analysis, including large scale geographic and digital elevation model analysis at the CyberGIS center at the National Center for Supercomputing Applications (NCSA) and capability to execute hydrology models (e.g. SWAT and RHESSys models) and connect to geoscience modeling communities (e.g. Landlab). A pending proposal for the next phase of HydroShare development would extend the capabilities of HydroShare to enhance support for model hypothesis testing using the Structure for Unifying Multiple Modeling Alternatives (SUMMA) approach, advance collaboration capability, integrate with 3rd party consumer cloud storage systems and establish an "App Nursery" to enable community coders to develop web apps linked to HydroShare. This presentation will describe the functionality and architecture of HydroShare comprising: (1) resource storage, (2) resource exploration, and (3) actions on resources by web apps. System components are loosely coupled and interact through APIs, which enhances robustness, as components can be upgraded and advanced relatively independently. The full power of this paradigm is the extensibility it supports, in that anybody can develop a web app that interacts with resources stored in HydroShare. We welcome discussion of the opportunities this enables for interoperability with other cyberinfrastructure tools, to the benefit of the hydrology and hydroinformatics research communities.