When water entitlement and water sharing systems are mis-specified, that is specified in a manner that lacks hydrological integrity, inefficient investment and water use is the result. Using Australia's Murray Darling Basin as an example, this paper attempts to reveal the economic consequences of entitlement mis-specification. Options for specification of entitlement and allocation systems in a way that has hydrological integrity are presented. It is reasoned, that if entitlement and allocation system were set up in this manner the result would be an efficient allocation regime that would autonomously adjust to climatic shifts, changes in prices and changes in technology whilst maintaining environmental integrity.