All water level observation systems are self-referential. In other words, the ‘raw’ data are relative to the position of the observation device, which is not very useful because data from different devices are not inter-comparable. This problem is resolved b introducing the concept of datum which is a zero plane that all water level observations are reference to. Unfortunately, for many historical, political and geographic reasons there are a multitude of datums. This report details the process disentangling datum confusion from a basin with international significance.