The directors may employ a general manager to have general charge of the work, paying such compensation as may be agreed upon by the directors. A director may be appointed as general manager at such compensation as may be fixed by the other directors, and when so employed he shall also perform the duties of a director, but shall not receive the compensation to be paid to the directors. The directors may also buy all necessary work animals, machinery and supplies and material of all description as may be required in the construction, operation or repairing of the improvements of the district, and may do and perform all things necessary and proper in carrying out the purposes of said district.