(3)"drainage-work" means any work in connection with a system of irrigation which has been or may hereafter be made or improved by the Government for the purposes of the drainage of the country, whether under the provisions of Part IV of this Act or otherwise, and includes escape-channels from a canal, dams, weirs, embankments, sluices, groins and other works connected therewith, but does not include works for the removal of sewage from towns:
