In Nepal, Farmer Managed Irrigation Systems (FMISs) dominate the number and the irrigated area. They were built and managed by farmers themselves for centuries. The main objective of this paper was to analyse the factors that made thes FMISs function well for so long. FMISs communities have indigenous but ultra-modern knowledge of layout, construction, management, ecology and hydrology. They have built irrigation structures in exceptionally difficult and varying geophysical environment without the aid of modern equipment. FMISs were constructed, operated and maintained for centuries with least damage and threat to environment and humanity. This study has found that perpetuation of accumulated experience, skill and the knowledge have enabled them balance water use, conserve natural ecosystem, generate employment and feed rapidly growing population, build social capital for collective action and maintain communal integrity, make best use of local resources and indigenous technology, and keep several FMISs alive. Centuries old live FMISs testify it. An in-depth study on FMISs doctrine and fine tuning them to respond to the current challenges will benefit not only the FMISs but also the entire humanity.
