The resources of the enviroGRIDS system are accessible to the large community of users through the BSC- OS Portal that provides Web applications for data management, hydrological model calibration and execution, satellite image processing, report generation and visualization, citizens oriented applications, and virtual training center. The portal publishes through Internet both the geospatial functionality provided by Web technologies, and the high power computation resources supported by the Grid technologies. The paper highlights the issues on the implementation of the portal by heterogeneous technologies, in order to support control flow, processing, and visualization of spatial data for GEOSS community, Earth Science specialists, and generally for Web users.