Hazard Assessment of Desertification as a Result of Soil and Water Recourse Degradation in Kashan Region, Iran

Desertification in arid, semi-arid and dry sub-humid regions is a global environmental problem. Considering the increasing importance of desertification and its complexity, the necessity of giving attention to desertification criteria and indices is essential. Models and methods such as MEDALUS, UNEP-FAO, and others have been proposed on local and national scales. In this research, IMDPA was selected from among different existing methods, and desertification intensity was evaluated on the basis of two criteria, soil and water, and 13 indices: soil depth, electrical conductivity of soil, texture, gravel percentage, drainage, sodium absorption ratio, type of geologic formation, slope, groundwater table fluctuation, electrical conductivity of water, color concentration, water crisis index, and water shortage for livestock and wildlife. Each criterion was assessed based on the selected indices which resulted in the qualitative mapping of each criterion based on the geometric average of the indices. Finally, a sensitive map of the region was extracted using the geometric average of all criteria. Thematic databases with a 1:50000 scale resolution were integrated and elaborated in a GIS based on ILWIS and arcGIS. Analysis of desertification criteria in the Kashan region showed that, among the studied criteria, water criterion is a major problem in the study area. It has a geometric average of 3.59 which shows very high class, while soil criterion with a weighted average of 2.12 stands in the medium class of desertification. The results also showed that groundwater decrease and water crisis index with a quantitative value of 3.72 classified in a very high class of degradation and depth with quantitative value of 1.20 classified in a low class of desertification were the most and least effective factors, respectively, among the studied indices on land degradation.