The licence had to specify the volumes of water abstracted, the location of the abstraction and the purpose, together w ith any conditions to protect the rights of existing abstractors and the needs of the environment. Although the act required eveiy licence to be assessed according to its reasonable need and its impact on the aquatic environment, over time the former has changed and the latter is now much better understood. In addition, changing patterns of demand have left many licences under-utilised, with no straight-forward mechanism for trading resources.