The full power and authority of the city is hereby extended over the territory and waters of Elm Fork for the purposes contemplated by this article. The city, through its department of public health and the police department and in behalf of the preservation of the public health, may order portions of the waters not to be trespassed upon by any person. It shall be deemed a trespass on the part of any person to swim, bathe or otherwise use the waters contrary to the terms of this article. The city may place guards for the purpose of guarding the waters against pollution and for the purpose of carrying out the terms of this article. (Code 1941, Art. 157-8)