This is the version 2.0 release (update; as of May 10, 2007) of the International Water Management Institute’s (IWMI’s) Global irrigated area map (GIAM) and associated products and data.

The GIAM products are produced using time-series data of: (a) AVHRR 10-km monthly from 1997-1999, (b) SPOT 1-km monthly for 1999, (c) GTOPO30 1-km elevation, (d) CRU 50-km grid monthly precipitation from 1961-2000, (e) AVHRR derived 1-km forest cover, and (f) AVHRR 10-km skin temperature. In addition JERS SAR data was used for the African and South American rainforests.

The front-page provides gateway to 4 product lines. The primary product, and overwhelming emphasis, is on Global Irrigated Area Map (GIAM). You can click on appropriate places in this front-page that will lead you to the above product line.

There are many unique features in the IWMI’s GIAM product line. First, this is the very first satellite sensor based global irrigated area map. Second, the resolution of the map (10-km) is the best that is presently available for irrigated areas at global level. Third, the area calculations are done for each season. So the area irrigated @ the end of the last millennium for the entire world was: (a) 257 Mha during June-September, (b) 174 Mha during October-February, and (c) 41 Mha during March-May. Further, there is a flexibility to calculate areas every month. Fourth, this is NOT just a map. There are suite of products that consists of maps, images, class characteristics, area calculations, snap-shots and photos, animations, and accuracies. There are numerous advantages of such a product line. For example, disaggregated class images can be downloaded and a more refined map can be created with local expertise for one’s area of interest. The irrigated areas are used to create a 20-year animations using AVHRR monthly time-series, so that one can spatially re-create the history of an irrigated area class. The class characteristics facilitate deriving crop calendar, sowing-peak-harvest dates of each class, and determine whether a class is single, double, or continuous crop. Fifth, the study develops and/or adopts a suite of innovative methods and techniques to map irrigated areas of the World at Global to local levels and at all resolutions or scale. The methods include spectral matching techniques (SMTs), image segmentation, decision tree algorithms and spatial modeling, data fusion, space-time spiral curves, brightness-greenness-wetness 2-dimensional feature space plots, NDVI time series plots, NDVI thresholds, principal component analysis, and unsupervised clustering algorithms. The wide array of ground truth data was also used. This included ground truth data of the Indus-Ganges river basins, Krishna river basin, IWMI’s ground truth data of the World that included data for Middle East and Africa, the degree confluence project data of the world, and the 150-m Landsat geocover mosaic of the world.