For the purpose of carrying out any one or more powers of a district, the governing body of any district may issue negotiable bonds of three general classes:
(1) bonds secured by ad valorem taxes;
(2) bonds secured solely by a pledge of all or part of the revenues accruing to the district, including but without limitation those received from sale of water, rendition of services, tolls, charges, and from all sources other than ad valorem taxes;
(3) bonds secured by a combination pledge of revenues and taxes.