4.—(1) The restriction on abstraction does not apply to any abstraction of water that is carried out by, or on behalf of, a navigation authority, harbour authority or conservancy authority in connection with its functions as such an authority if—
(a)the purpose of the abstraction is a transfer of water without intervening use,
(b)the abstraction is an emergency abstraction as defined in paragraph (2), and
(c)the authority gives notice in accordance with paragraphs (3) and (4) (but see paragraph (5)).
(2) An abstraction of water is an emergency abstraction if, in the opinion of the authority, an emergency has arisen which makes the abstraction necessary to prevent immediate danger of interference with any operations relating to that authority or, in relation to such operations, to prevent an immediate risk of—
(a)death, personal injury, or harm to health of a human being,
(b)damage to property, or
(c)damage to the environment.
(3) The authority referred to in paragraph (2) must give notice to the appropriate agency of —
(a)the fact that the abstraction has taken place and of the source of supply in question, and
(b)the reason that the authority considered that—
(i)an emergency had arisen, and
(ii)the abstraction was a necessary measure to prevent an immediate danger or risk identified in paragraph (2).
(4) Notice under paragraph (3) must be given before the end of the period of five days beginning with the date on which the abstraction started.
(5) On receipt of a notice under paragraph (3), the appropriate agency may give notice to the authority that—
(a)in the appropriate agency's opinion an emergency has not arisen, or
(b)that the abstraction is not, or is no longer, necessary for any of the reasons set out in paragraph (2).
(6) If the appropriate agency gives notice under paragraph (5), the restriction on abstraction applies to the abstraction from the time when the notice is served (and, where appropriate, the restriction imposed by section 24(2) of the 1991 Act also applies accordingly).