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Subsurface drainage is a current of irrigated agriculture under arid and semi arid climates. Most of Magherb (Maroc, Tunisia, Algeria) large schemes have been installed in the 70-80's. These three countries are preparing "green plans" meaning plans for agriculture intensification and promotion of irrigation re-engineering for both existing and future schemes. The background of these plans is to reduce to nil the water losses, that implicates to apply less irrigation water than required by crops. In this context what should be the place of drainage: are existing drainage to be rehabilited and future systems likely to be equipped with tiles ? if yes, according to which design criteria and environmental stakes? here are the basic questions of the paper. In first place the aim of drainage and the current design criteria are reviewed in the three countries. After what we will highlight the issues of the re-ingeneering from an analysis of the current situation the irrigation schemes; for this purpose we will issue monographies of three irrigation schemes, the choice of which being based on a typology. The monographies will report of more than 10 years of north/south cooperation including performance assessment, gray literature, results of on farm experimentation, farmer's practices. The three choosen schemes browse various climatic conditions from Humid Mediterranan (Gharb, Morocco) to arid (Bas Chelif, Algeria) and Saharian (Fatnassa oasis, Tunisia) and various sizes from 100000 ha, 7 000 ha, 300 ha respectively.