The Impact Assessment of Temporal Variation of Climatological and Groundwater Condition on Desertification Intensity in Garmsar Plain

Desertification consists of land degradation in arid, semi-arid and dry sub-humid areas induced by climate change and human activities. For evaluation and mapping of desertification many research have been conducted leading to regional and local models. In this research, among different existing methods, IMDPA‌ model was selected and desertification intensity of Garmsar plain was evaluated based on 2 criteria and 6 indices including: climate (precipitation, drought and aridity index) and water (groundwater table depletion, electrical conductivity, sodium absorption ratio) over four periods; 1995-1997, 1997-2003, 2003-2009 and 2010-2012. Each criterion was assessed based on the selected indices resulted in qualitative mapping of each criterion based on geometric average of the indices. Finally, desertification map of the region was extracted using geometric average of criteria for each period. Thematic databases, with a 1:50000 scale resolutions were integrated and elaborated in ArcGIS9.3. The results showed that during the periods, four indices including groundwater table depletion, electrical conductivity, aridity index and precipitation index have the most significant effects on desertification with the values of 3.81, 3.17, 3.11 and 3.09, respectively. Also two indices including Sodium absorption ratio and drought have the least effect on desertification with the values of 1.17, 1.63 of the Plain, respectively. Also, analysis of desertification criteria in Garmsar region showed that among studied criteria, water criteria have had the most effect on land degradation and desertification since 1994.