Several adaptive systems have been proposed that are based on the concepts of smart cities, which can be successfully adapted to natural disasters or other public safety concerns. Since these systems are embedded in a critical and dynamic environment, it is really important to have an infrastructure that is capable of providing real-time environmental information. This paper discusses two research questions that arise from adaptive ubicomp systems: (i) what are the key requirements to provide a reliable WSN-based system (e.g. a river monitoring system)? and (ii) how can an adaptable and reliable WSN-based system be developed? This paper seeks to respond to the former question with the aid of the RESS standard platform. The latter question is answered by employing a generic approach for adaptation. The term “critical systems”, means that any error may result in the loss of human life. We devised the RESS standard after deploying the WSN-based river monitoring system in Brazil for five years. Our prototype underwent several trials, sometimes leading to failure or damage, before we came up with a more reliable solution, which is outlined in this article. Finally, while our RESS platform is policy-free, it is extensible/adaptable and hence can naturally be adapted to new policies.