The holder of a licence under this Act may apply to the river authority to revoke the licence; and on any such application the river authority shall revoke the licence accordingly.

The holder of a licence under this Act may apply to the river authority to vary the licence; and the provisions of sections 28 and 29 and 38 to 41 of this Act shall apply (with the necessary modifications) to applications under this subsection, and to the variation of licences in pursuance of such applications, as they apply to applications for, and the grant of, licences under this Act:

Provided that, where the proposed variation is limited to reducing the quantity of water authorised to be abstracted in pursuance of the licence during one or more periods, sections 28 and 39 (4) of this Act shall not apply.