All payments due or to become due to the United States under any contract between the district and the United States, including such payments of interest and principal on bonds as may be required in connection with a deposit or transfer thereof to the United States, shall be paid, unless otherwise provided by contract, by revenue derived from annual assessments apportioned as prescribed in this chapter, and levies thereof upon such real property within the district as may be assessable for district purposes under the laws of the State or by tolls and charges, as the case may be. Such real property shall be and remain liable to be assessed and levied upon for such payments.
NRS 539.310