Mapping irrigated area in Mediterranean basins using low cost satellite Earth Observation

Excessive use of irrigated water in the Mediterranean has deteriorated the freshwater resources by depleting the aquifers, discharging agri-chemicals and accelerating saltwater intrusion. Several European directives outline that estimating the extent of irrigated areas in each water basin is a primary step towards sustainable natural resources management. This paper aims to identify a low cost methodology for mapping irrigated area in Mediterranean basins, using satellite Earth Observation. After evaluating several combinations of land feature mapping techniques on digitally enhanced satellite images, the one with the highest accuracy has been identified (thresholding of the second principal component). The methodology was formulated under the assumption that irrigated land can be identified by the result of irrigation, i.e. the existence of green vegetation in the semiarid summer, thus avoiding costly field surveys, and using low cost satellite imagery. The proposed methodology has been applied to two Mediterranean basins with conflicting agronomic and ecological interests, which were of a different scale. The resulting irrigated area map achieved high accuracy (up to 98.4%) and reliability (up to 0.967) in both basins. The results were also displayed as irrigation intensity to improve visualisation and help identify areas of high environmental pressure on nearby wetlands. (C) 2008 Elsevier B.V. All rights reserved.