There is no need for an explicit crop identification to make a map of the irrigated areas.
The National Oceanic Atmospheric Administration-Advanced Very High Resolution
Radiometer (NOAA-AVHRR) is providing vegetation indices on a regular basis and at
low costs, which make it suitable for land use determinations of large areas. Kite and
Droogers (1999) surveyed the major agro-ecological zones in the Gediz River Basin
(Turkey) using NDVI from AVHRR and merged it with digital elevation information.
Although small-scale activities such as the cultivation of vegetables will not be captured
with 1.1 km AVHRR images, this technique allows a fast delineation of a basin into the
major agro-ecosystems (Kite, 1995). NOAA-AVHRR has also been frequently applied at
continental scale (Fuller and Brown, 1996).