The Black Sea Catchment area is well known for subjects such as ecologically unsustainable development or inadequate resource management. The EnviroGRIDS project addresses these issues by using emerging information technologies. The enviroGRIDS Web Portal allows the users to access the geospatial functionality given by Web infrastructure, and to high power computation resources given by Grid infrastructure. The Black Sea Catchment Observation System portal provides a single point of access to the enviroGRIDS applications and tools. Both the vertical and horizontal interoperability are available between the platforms and applications throughout the portal. The horizontal interoperability is accomplished through services, meaning the applications are working together by the exposed services. The vertical interoperability is supported by the communication between the layers of end user applications, Web infrastructure, and Grid infrastructure. The basic solution of interoperability is accomplished by services, messages, and data. The paper highlights the solutions developed by the Black Sea Catchment Observation System portal to support various types of interoperability between the modules of geospatial data management, hydrological model calibration and running, satellite image processing, spatial data visualization, and virtual training center.