The owner of a watercourse has a property right in the watercourse. That includes a right to preserve the quality of the water. That right is protected by the common law. The discharge of polluting effluent is an actionable nuisance if the pollution interferes with the use or enjoyment of the property.
A body which exercises statutory powers, such as a sewerage undertaker, is liable in the same way as any other person if it is responsible for a nuisance, trespass or other tort, unless either it: (i) is acting within its statutory powers, or (ii) has been granted some statutory immunity from suit. If a sewerage undertaker interferes with a person’s rights, it is therefore necessary to distinguish between interferences which Parliament has authorised, which are lawful, and interferences which Parliament has not authorised, which are unlawful. When drawing this distinction, two principles are relevant. First, a person’s rights to the peaceful enjoyment of its property and to access the courts are protected by both the common law and the Human Rights Act 1998. The principle of legality holds that fundamental rights cannot be overridden by general or ambiguous words. A statute will, therefore, only authorise what would otherwise be an unlawful interference with property rights, or deprive a person of the right to bring a legal claim, if this is clear from or a necessary implication of the express language used by Parliament. Secondly, Parliament will not be taken to have intended that statutory powers should be exercised, or duties performed, in a way which interferes with private rights, unless the interference is inevitable.
The issue before the Supreme Court in MANCHESTER SHIP CANAL COMPANY LTD v UNITED UTILITIES WATER LIMITED (2024) UKSC was whether, as a matter of statutory interpretation, the Water Industry Act 1991 excluded common law rights of action in nuisance and trespass. The Supreme Court held that it did not.