Mapping and Assessment of Land Degradation Risk using MEDALUS Model in Siyahpoush Watershed, Ardabil Province

Nowadays, land degradation is a serious problem in many parts of the world. Land degradation occurs as a result of various factors including climatic change, improper land use and management in arid, semi-arid and dry sub-humid areas. It has been recognized as a major socioeconomic, social and environmental problem in many countries of the world. Various models are provided in order to assess desertification in the world. It seems that the MEDALUS model has apparent advantages compared to the other ones, such as easy style, data accessibility and taking geometric mean. The objectives of this study were to mapping and quantitative evaluation of land degradation in Siyahpoush catchment using MEDALUS and adjusted MEDALUS model.
In this study, MEDALUS and adjusted MEDALUS models were applied to desertification assessment and mapping in Siyahpoush catchment. For this purpose, four important criteria (soil quality, climate, vegetation cover, management and policy) which were effective on desertification have been selected. Indices for each criterion are defined in the MEDALUS model. Index layers for each criterion were prepared using GIS. These indices were ranked in accordance with MEDALUS model. The geometric mean was then calculated and map was produced for each criterion. Land degradation map of the study area was finally prepared using the geometric mean criteria.
The result showed that management quality and climate quality criteria with a geometric average of 1.91 and 1.62 have played the most important role in sensitivity of the area to desertification. Soil quality criterion with a geometric average of 1.39 and vegetation quality criterion with a geometric average of 1.41 were classified in moderate and high quality, respectively. Therefore, vegetation quality was determined as the most appropriate criterion. The ESAI index for MEDALUS and adjusted MEDALUS model ranged 1.38 to 1.79 and 1.37 to 1.93, respectively. This means that all area is located in critical class of desertification.
The management and climate quality were identified as the most inappropriate criteria and vegetation quality was found as the most appropriate criterion. According to the obtained results, the study area is classified as critical class by ESAs model, so that 90.1% and 99.2% of the study area is located in the severe critical sub-class (C3) whit MEDALUS and adjusted MEDALUS model, respectively. However, implementing management policies would help to restrain this phenomenon at field or regional level. In addition, monitoring of land degradation needs to be considered that have involved more effective indices in this region.