The map shows the amount of area equipped for irrigation around the turn of the 20th century as a percentage of the total area on a raster with a resolution of 5 arc minutes. The area actually irrigated was smaller, but is unknown for most countries. A special note has to be made for Australia and India where the map shows the total area actually irrigated. This is due to the fact that statistics collected in Australia and India refer to actually irrigated area as opposed to statistics with area equipped for irrigation which are collected in most other countries. An explanation of the different terminology to indicate areas under irrigation is given in a glossary.

Since 1999 the methodology to produce the map has been improved which made it possible to increase the spatial resolution of the map to 5 arc minutes (about 10 km at the equator). The objective of the cooperation between the Universities and FAO is to develop global GIS coverage of areas equipped for irrigation and to make it available to users in the international community. The data collected through the AQUASTAT surveys will be used to improve the overall quality and resolution of the information.

A digital interactive map, a static global map, downloadable spatial data, and full metadata for each region are available on the website.