Any district issuing revenue debentures, notes, warrants, bonds, or other evidences of indebtedness is hereby specifically authorized and empowered to pledge all or any part of the revenue which the district may derive from the sale of electrical energy, hydrogen produced for use in fuel processes, ethanol produced for fuel, storage of water, water for irrigation, radioactive material or the energy therefrom, or other service as security for the payment of the principal and interest thereon. Any such pledge of revenue shall be made by the directors of the district by resolution or by agreement with the purchasers or holders of such revenue debentures, notes, warrants, bonds, or other evidences of indebtedness.