Irrigation has always been a way of enhancing the suitability of land for agricultural production. It can take place in an arid environment, where agriculture is otherwise not possible, or it may be practised in more favourable environments, either to protect production from climate irregularities or to increase cropping intensity.g Irrigation increases the suitability of most land where water, and therefore climate – in particular the rainfall regime – is the main constraint to production.
Over the years, the push for greater productivity has resulted in increased access to irrigation (see Figure 21), making agriculture by far the main water use sector and pushing the limits of sustainability in an increasing number of regions.
Figure 21 Trends in land under irrigation and rainfed cropping, 1990–2020
SOURCE: FAO. 2025. FAOSTAT: Land Use. [Accessed on 13 February 2025]. https://www.fao.org/faostat/en/#data/RL. Licence: CC-BY-4.0.
The possibility for further expansion of irrigated agriculture depends largely on the levels of water stress. SDG Indicator 6.4.2 measures water stress as the ratio of total freshwater withdrawn to the total renewable freshwater resources within a specific region, after considering environmental flow requirements. This metric quantifies the degree to which water use impacts the sustainable replenishment of freshwater resources in a given area. Values below 25 percent can be considered safe under any circumstances (no stress). Beyond the 25 percent threshold of water stress, four classes have been established for SDG Indicator 6.4.2 to indicate different levels of stress severity (low, medium, high and critical).
In this context, regions with lower water stress have more water available for the expansion of irrigated areas, while regions with high water stress find themselves in a situation of competition within and across sectors. Figure 22 illustrates the findings from the 2024 status report of SDG Indicator 6.4.2 (FAO and UN-Water, 2024).
Figure 22 Level of water stress by major river basin, 2018–2021
NOTE: Numbers in brackets indicate the ratio of total freshwater withdrawn to the total renewable freshwater resources.
SOURCE: FAO & UN-Water. 2024. Progress on the level of water stress – Mid-term status of SDG Indicator 6.4.2 and acceleration needs, with special focus on food security – 2024. Rome, FAO. https://doi.org/10.4060/cd2179en
The map may be interpreted as showing that there are still many areas where water availability is not an issue. However, these are mostly areas with abundant precipitation and little need for irrigation, while in the subtropical areas on both sides of the Equator, where precipitation is scarce, there are very few areas with low levels of water stress. Areas where existing yields can be boosted by applying water in agriculture are primarily located in sub-Saharan Africa, where yields are generally low and water is available, and to a lesser extent in Latin America. In most of Asia, irrigation is already practised on a large scale.
The physical dimension of water stress illustrated by SDG Indicator 6.4.2 represents just one dimension of water scarcity. Other dimensions of water scarcity (FAO, 2012) include the economic dimension, by which water may be abundant, but financial resources are not available to develop the infrastructure needed to take advantage of it. Institutional and organizational scarcity, or scarcity of accountability, refer to the lack of capacity of institutions to respond to the need to access water in the right place at the right time.
