Corporations availing themselves of the privileges conferred by La. Rev. Stat. 45:61 and 45:62 and by Art. 13, Section 6 of the Constitution are deemed public service corporations within the territory selected by them for the distribution of water.  La. Rev. Stat. 45:61, however, does not confer the right of expropriation upon existing canal systems nor declares existing canal systems public service corporations.