Sustainable Yields Module (SY) 3a provides improved representation of groundwater modelling. It involves the development and evaluation of a method for estimating historical baseline recharge across the MDB and changes in the recharge under future climate. This includes three components of the recharge that will be important in different areas of the Murray–Darling Basin; diffuse recharge from rainfall, the instream recharge from losing streams, and the overbank flood recharge.