The trustees are the corporate authority of the district and shall manage and control the affairs, property, and facilities of the district. The board of trustees shall elect a president, a clerk, and a treasurer from its membership. The trustees may certify for levy an annual tax as provided in section 357E.8 . The trustees may construct, reconstruct, repair, maintain, or operate a dam or other recreational facilities or structures to create or maintain an artificial or natural lake or impoundment and may promote and improve water quality. For these purposes, the trustees may purchase material, employ personnel, acquire real estate and interests in real estate, and perform all other acts necessary to properly maintain and operate the district. The trustees are allowed necessary expenses in the discharge of their duties, but they shall not receive a salary.