Many large-scale state-run irrigation projects in the world have been constructed with limited investment in on-farm infrastructure. In most cases, it was expected that local farmers would themselves make improvements on their farms. In general, insufficient attention is paid to water control which has a negative impact on productivity. Farmers' strategies to offset poor access to water are very varied and depend on site-specific factors such as topography, the existence of other potential water sources, market opportunities or capital availability. This article presents a case study in the Central Plain of Thailand and describes the patterns of land development which occurred since the construction of the Irrigation Project 25 years ago. It shows how land and water use evolved as both a mover and a response to on-farm development and who initiated new investments, such as ditch and tube-well digging, regulators in drains, which have allowed secondary water sources to be tapped, the development of conjunctive use, increased reliability in water supply and crop diversification. The importance of individual farm pumps is shown. Poor land levelling is conducive to high costs and reduced water use. Prospects for land consolidation are assessed.