Environmental databases store a wide variety of data from heterogeneous sources which are described with domain-specific terminologies and refer to distinct locations. In order to make them accessible also to non-expert users, terminological concepts and spatial relations must be represented in a way that they can be exploited for searches. In this paper we propose a hybrid knowledge representation system architecture which integrates terminological and spatial aspects of the application domain and provides support for reasoning with RCC, a well-known calculus for spatial reasoning, and the Semantic Web's ontology language OWL. Our approach is motivated by the observation that RCC cannot be expressed in OWL without a major revision of the latter. Issues of upholding consistency of the knowledge base in view of an evolving ontology and of computational complexity are discussed.