Except as otherwise specifically provided, the commission shall administer the provisions of this chapter and shall establish the level of quality to be maintained in, and shall control the quality of, the water in this state as provided by this chapter. Waste discharges or impending waste discharges covered by the provisions of this chapter are subject to reasonable rules or orders adopted or issued by the commission in the public interest. The commission has the powers and duties specifically prescribed by this chapter and all other powers necessary or convenient to carry out its responsibilities. This chapter does not apply to discharges of oil covered under Chapter 40, Natural Resources Code.