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GCOS Terrestrial ECV T2
Water Use
Introduction: The availability of freshwater plays a crucial role in food production and food security. Irrigated land covers about 20% of cropland but contributes about 40% of total food production. Irrigated agriculture accounts for about 70% of all freshwater consumption world-wide and more than 80% in developing countries. Future food needs will require intensified production, including the increased irrigation of agricultural crops that is expected to raise water consumption, and hence such production will become more sensitive to drought. In order to obtain improved quantitative and qualitative information on irrigated land and available water resources, data on their spatial distribution and change over time are essential.
Information on changes in the area of irrigated land and the amount of water used for irrigation is necessary in order to diagnose how much changes in other terrestrial ECVs (e.g., land cover, melting of glaciers, river discharge, and lake level/area) are caused by climate change as distinct from land-use and water-use changes.
The FAO defines requirements for information on irrigation water use by international, regional, national and local communities and archives and disseminates information related to irrigated water use through its on-line AQUASTAT database on water resources and irrigation, available on the web.
Most products are incomplete, but two global products are available, namely the Global Irrigated Area Map (GIAM), developed by the International Water Management Institute (May 2007 update), and a map of irrigated areas, prepared by the University of Frankfurt, Germany in collaboration with FAO and available through AQUASTAT. Finer resolution products are available for some regional and national areas. A priority is production of gridded global datasets of irrigated area using satellite data at 250 m resolution on a regular basis. Attention should be given to this in future land-cover databases (see ECV Land Cover). Whereas satellite data analysis is fairly simple for semi-arid/arid areas, more complex analysis of seasonal datasets is needed to identify irrigated areas in temperate and tropical zones. For proper assessment of water use, regular information on the timing and frequency of irrigation is also needed in addition to mapping of irrigated areas. Information on total water uptake (not limited to groundwater abstraction) for irrigation is essential to assess the potential effects of climate change and variability, and data available from the UN Statistics Division (using the UN System of Economic and Environmental Accounting) may be of additional value.
The in situ information required to complement satellite data, e.g., on the source of irrigation water (surface, lake, river, groundwater, local, or extra-local), the type of irrigation (surface, sprinkler, or micro-irrigation), the timing and frequency of irrigation, or the volume of irrigation water used is generally not available. However, research projects could support the eventual integration of satellite and in situ measurements such as improvements in land-cover characterisation.
There is a need for more quality assurance of data to be submitted to the database and FAO is developing a new set of guidelines and protocols for national reporting.
(Source: WMO/IOC Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (2010 Update) GCOS-138/GOOS-184/GTOS-76/WMO-TD/No. 1523)
References:
Data, Product, Metadata and Information Access
[ECV Matrix Main Page] [About the ECV Matrix] [Reference Documents] [Contact] [Updated June 6, 2010]
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Non-satellite or in-situ
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Satellite
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