The CSIRO is one of the participants in the development of WaterML v2.
The goal of WaterML v2 is harmonization of WaterML with the Observations and Measurements (O&M) data model and encoding and Sensor Observation Service (SOS) interface. O&M and SOS are from Open Geospatial Consortium (OGC), and O&M is on track to become an International Standard ISO 19156. Harmonization would enable (a) delivery and consumption of water observations data using systems developed to conform to the SOS standard (b) integration of water observations data with information from closely related domains in environmental sciences, such as geology and meteorology, where OGC-conformant systems are being deployed (e.g. OneGeology).
If you are interested in this initiative and you would like to gain access to the project wiki please contact Peter Taylor at CSIRO.