Abstract: For some emergency situations an effective response can be reliant on sensor data (e.g. river level, traffic flow, weather conditions) to provide situation awareness, in order to help authorities make informed decisions. Gathering data in a traditional approach, i.e. using precise physical sensors, is a highly expensive task, involving procurement, installation and maintenance of a number of sensors. As a result, the coverage of sensors is limited and only the regions deemed most important by authorities are monitored. However, regions currently not being monitored can have an urgent need to be sensed depending on emergencies or situations. We present a high-level overview of the Locaware system, which employs a flexible geofencing approach to enable crowdsourcing by requesting citizens and volunteers to help authorities formulate a greater situation awareness of a region under consideration. While the Locaware system is motivated for water monitoring, our approach can be applied in other contexts.