This paper compares the relative advantages of improvements in practices and changes in cropping system patterns in order to manage water resources at catchment basin level and thus preserve the cropping systems over the long term. When water for irrigation comes from large aquifers belonging to the catchment basin itself, the cropping systems pattern is the crucial factor because it determines the annual supply of water to the aquifers in order to match the total water demand. When water for irrigation is surface water coming from rivers or other reservoirs, both practices and cropping systems play an active role in fitting water demand to water supply. Whatever the origin of irrigation water, a greater diversity of cropping systems will be an advantage when there is a shortage of water.
