Erosión y desertificación.-Risk assessment of desertification using GIS in parts of Mond Basin, Southern Iran

Abstract

ABSTRACT The present paper attempts to evolve a new model by considering various indicators of different types of land degradation or desertification, namely, water erosion, soil salinity, vegetation degradation, and lowering of ground water table. The Mond river basin, located centrally to this zone, has been selected as a test area to assess the risk and kind of desertification. For this purpose two sub basins of the Payab and Qareh Aghaj have been chosen for detailed study. The thresholds for the severity classes of indicators have been established and then the hazard map for each indicator of types of desertification has been prepared in a GIS. The risk maps of water erosion, soil salinization, lowering of water table, vegetation degradation have been produced for each of the two sub basins. It was possible to distinguish the areas under ‘actual risk’ from areas under ‘potential risk’ of desertification types. Also areas under potential risk are classified to subclasses with different probability level to show a statistical picture of risk in future. The final map of risk of desertification is produced by overlaying all four maps of degradation types. Between the two basins the overall environmental condition in the Payab sub basin is worse. Results show that potential risk areas are much widespread than areas under actual risk in the upper reaches (Qareh Aghaj sub basin) of Mond basin, indicating further threat of land degradation or desertification in future. While per cent areas under actual risk are much extensive in the lower reaches (lower reaches), indicating the higher degradation at present.