The development of models using multiple modelling paradigms is necessary to formulate and study current problems in environmental science. To simplify the coupling of those models, a formal basis for a high-level specification of such models must be set up. In this paper, we propose a discrete event system specification (DEVS) based modelling framework as a formal basis in environmental modelling. The formal framework ensures that the models are reusable and interoperable components with well defined interfaces. Moreover, a wide variety of modelling paradigms can be expressed in the DEVS formalism. We also extend the modelling paradigms that can be expressed in the DEVS framework with two techniques: Feedback-DEVS for the specification of supervised-learning models and Vector-DEVS for the specification of models in vector space. JDEVS is the Java implementation of the framework. It enables discrete event, general purpose, object oriented, component based, GIS connected, collaborative, visual simulation model development and execution. A Feedback-DEVS neural-network model and a cellular infiltration model are described as experiments using JDEVS. Those models are later coupled to show the new modelling scenarios enabled by the use of a formal framework and the flexibility of the software.