A district whose facilities are for delivery primarily of agricultural water supplies and wherein at least 51 percent of the assessable acreage is zoned and developed for agricultural uses may issue revenue warrants pursuant to this chapter to obtain funds for any lawful purpose of the district, including the repayment of indebtedness of the district. A district may issue revenue warrants pursuant to this chapter in any year only if the district does not receive during such year its full contractual entitlement under a water supply contract with the United States, the State of California, or any other public agency, upon which contract the district relies for meeting a substantial portion of its water supply needs.