Department of Irrigation (DoI) is a government organization, with a mandate to plan, develop, maintain, operate, manage and monitor different modes of environmentally sustainable and socially acceptable irrigation and drainage systems – from small to larger scale surface systems and from individual to community groundwater schemes. Its ultimate aim is to provide year round irrigation facilities and increase the irrigable area of the country to higher limits. This giving a primary input in increasing the productivity of the land and providing a major input to the GDP and eventually improve the standard of living of the beneficiary farmers. Apart from this the DoI also has to carry out river training activities to protect the floodways, floodplains and agricultural lands in the form of river bank protection such that the loss of properties caused by flooding is reduced.

Although the construction of modern irrigation system started in Nepal in 1922 during Rana regime with Chandra Nahar, the Department of Canal was formally established in 1952 under the ministry of Construction and Communication. The department then passed different stages working under different ministries and finally ended up as Department of Irrigation in 1987. Since the establishment of Ministry of Irrigation (MoI) in 2009, DoI has been working under it.