The metropolitan district shall have as its duty the development, operation and maintenance of a public system of interconnecting trails and parks throughout the counties comprising the district, including any areas under concurrent jurisdiction with an agency of the United States government. Nothing in this section shall restrict the district’s entering into and initiating projects dealing with parks not necessarily connected to trails. The metropolitan district shall supplement but shall not substitute for the powers and responsibilities of the other parks and recreation systems within the metropolitan district or other conservation and environmental regulatory agencies and shall have the power to contract with other parks and recreation systems as well as with other public and private entities. Nothing in this section shall give the metropolitan district authority to regulate water quality, watershed or land use issues in the counties comprising the district.