A large variety of water models exist, each tailored to address specific challenges related to hydrologic science and water resources management. When scientists and engineers apply one of these models to address a specific question, they must devote significant effort to set up, calibrate, and evaluate that model instance built for some place and time. In many cases, there is a benefit to sharing these computer models and associated datasets with the broader scientific community. Core to model reuse in any context is well-defined metadata for describing the model. A standardized metadata framework applicable across models will foster interoperability and encourage reuse and sharing of existing resources. This paper reports on the development of a metadata framework for sharing water models. We also discuss steps taken to implement the resources and metadata framework in the HydroShare system. As an example of the potential benefit of a common model metadata framework, we will present the prototype of a SWAT Model Instance resource type that can used to provide interoperability between the HydroShare system and an external system called SWATShare that is tailored for running SWAT models in the cloud, but lacks the general resource sharing capabilities and goals present in HydroShare. This example is a demonstration of our long-term vision: to establish a common metadata framework for water models that enables interoperability across cyberinfrastructure systems.