Hi Simon, maybe I don't ...

Hi Simon, maybe I don't understand your groundwater monetization system properly.  I would have thought that the key issue to prevent depletion of groundwater resources would be to ensure that abstraction is less than the recharge rate, and hence managing abstraction is first and foremost the main requirement to ensure sustainable utilisation.  This involves not only a pump yield test, but also a proper assessment of the recharge of the aquifer under different rainfall scenarios (e.g. 10 year drought).  However if your approach helps to ensure license holders do not over-pump the aquifer (pump more than they are licensed to abstract), then I am in the picture.  In South Africa farmers using more than a base amount of water (either surface or underground) are required to meter and report the quantities used.  They are charged accordingly.  However it is difficult to monitor whether the reporting is a true reflection of actual use.