The iconic status in which northern Australia is viewed by an increasing number of people is due largely to the unique and diverse ecological systems which have evolved in response to the interplay between the landscapes, rivers and strongly monsoonal weather patterns. Because tropical rivers discharge some 70 per cent of Australia's fresh water there is also increasing pressure from various quarters to extract some of the water for irrigation. There is recognition by most however that mistakes have been made in other parts of Australia and around the world, where many key irrigation systems are now degraded or degrading, and no one wants to see that repeated in northern Australia. In this paper we discuss activities underway to build an understanding of northern tropical catchments to better inform the debate about whether to irrigate, and if so, what irrigation should look like, where it should be located, and how it should be managed. We discuss in particular issues to do with tropical water systems, 'water availability', and the potential role of groundwater as the main supply for irrigation water. The expectation is that any new irrigation and modification of existing irrigation schemes must ensure that the benefits of irrigation outweigh long term social and environmental costs.