The entire proceeds from such guaranty fund levy shall be deposited by the treasurer of such conservancy district in a separate fund to be known as the guaranty fund, and so long as any bonded indebtedness of such district remains outstanding and unpaid, the guaranty fund may be used only to pay the principal of and interest upon the bonded indebtedness of the district as the same shall mature, and then only when and if the district does not have on hand other funds available for such purposes.