The exercise of the powers granted by this article will be in all respects for the benefit of the people of the state for the purpose of conserving natural resources, for the increase of commerce and prosperity and for the improvement of health and living conditions. Since the operation and maintenance of projects authorized by this article will constitute the performance of essential functions, the bonds authorized by this chapter and the income therefrom and all mortgages executed as security therefor shall be exempt from all taxation in the State of Alabama.