Section 3. The division shall keep all bridges built by it across the reservoir upon the Nashua river safe, and shall have charge of, use, maintain and operate the same, and the commonwealth shall be exclusively responsible for all damages caused thereby or by any defect or want of repair therein. The department shall have the exclusive right and control over all ponds, reservoirs and other property within the watershed system, and may order all persons to keep from entering in, upon or over the waters thereof and the lands of the commonwealth or towns surrounding the same.