The WARM model is the result of the activities of an open research group involving researchers and technicians working on different aspects of rice cultivation and modelling. The objectives of this scientific exchange are the development of a simulation model for flooded rice able to manage all the main aspects influencing crop production, and the collection of high quality data to support development and evaluation activities. Interdisciplinarity is considered a key concept for the WARM team as crucial for developing coherent models, that is models which are not characterized by extreme levels of complexity in the representation of some processes and lack of information in other compartments of the system studied. The model currently includes components for the simulation of crop growth and development, water dynamics under flooded conditions, floodwater effect on vertical thermal profile, spikelet sterility, and effect of blast disease on growth. Other modules are under development. In order to increase model robustness through the collection of information about its suitability in a wide range of conditions, specific attention has been dedicated to increase the usability of the model. For this reason, we have integrated in WARM tools (i) for Monte Carlo based sensitivity analysis, (ii) for automatic calibration (based on simple and genetic evolutions of the simplex), and (iii) for evaluation of model performances. Preliminary studies about the evaluation of the relevance and performances of WARM in comparison with models of large use worldwide (i.e. CropSyst and WOFOST) in Northern Italy underlined that the model is able to simulate crop growth with the same level of accuracy but with a low total number of parameters, which are balanced in terms of influence on model outputs. A version of WARM linked to the MARS database is currently used by the European Commission for rice yield forecasts at European level.JRC.I.6-Biotechnology and GMO