Many decision makers are hindered in their daily work by “un-integrated” systems which can force them to move data around between tools which are only more or less compatible. Because environmental models play an important role in environmental decision support systems, the integration of models into user-friendly integrated decision support systems is essential to the support of such users. This paper presents a decision support system supporting users involved in the protection of the Coatzacoalcos River in Mexico near the largest agglomeration of petrochemical installations in Mexico, which are operated by the Mexican oil company Petroleos Mexicanos. At the same time, the area is densely populated and important for agriculture.The system was built in a collaboration of the Mexican Petroleum Institute, the Environmental Informatics Group, and cismet GmbH and is based on cismet’s geospatial application suite called cids. It integrates several tools and models into a holistic, user-centered application.