Abstract: Methods and systems are provided for intelligently detecting pipeline small leaks and thefts. In the Energy Flow Line Method, measured changes in flow data at both ends of the pipeline are monitored and analyzed to detect a leak or a theft. The energy wave front speed and the unsteady flow mathematical model of the subject pipeline is used to calculate leak details. In the Filtered Pressure Waves Method, the measured pressure data at both ends of the pipeline is monitored and analyzed. Pressure waves that do not originate at the ends of the pipeline are selected. Two travelling time windows are applied to those candidates, and the candidates are processed within each window. Leaks, thefts and their details are obtained if the detected leak locations meet the criteria. The Enhanced Filtered Pressure Waves Method, provides the leaked amount and verifies the leak and the leak location to avoid false alarms.