Cloud-based data management systems are more conducive to collaborative efforts when they are integrated with cloud-computing tools that interact with their stored data. HydroShare, a web based data management system for climate and water data, has implemented an Application Programming Interface and a web application platform deployed using Tethys Platform to encourage the development of apps that interact with its data. HydroShare GIS is the result of one such development effort to provide cloud-based visualization of spatial data stored in HydroShare. It functions by accessing the spatial metadata contained within the HydroShare resource data model and overlaying datasets as layers within the OpenLayers JavaScript library. Data are passed from the app’s server to a GeoServer data server and shared as web mapping service layers. Thus, users can easily build map projects from data sources registered in HydroShare and save them back to HydroShare as map project resources, which can both be shared with others and re-opened in HydroShare GIS. This paper will describe the design of the HydroShare GIS app and the cyber-infrastructure that supports it, and evaluate its efficacy as a web based mapping tool
