For the payment of all or part of the costs of an improvement project or services, the board may issue bonds in one or more series payable from and secured by ad valorem taxes, assessments, impact fees, revenues, grants, gifts, contracts, leases, or any combination of those funds. Bonds may be liens on all or part of the revenue derived from improvements authorized under this chapter, including installment payments of special assessments or from any other source pledged to their payment.
Tex. Loc. Gov't. Code § 375.201