Longterm Land use Change Detection in Mahidasht Watershed, Iran

Changes in land use are considered as significant factors by decision makers which can be precisely evaluated by Geographic Information System (GIS) and Remote Sensing (RS) techniques. However, land use alteration should also be evaluated for monitoring and curtailing the land degradation, especially deforestation and degradation of rangelands. The present research was then carried out in the Mahidasht Watershed, a western semi-arid region in Iran for evaluating land use change during 1955- 2017, using aerial photos (1955) and Landsat satellite images (TM 1989, ETM 2002 and 2017). The main land use types of the study watershed including agriculture, forest and, rangeland and mix land use boundaries were mapped for each period (1955, 1989, 2002 and 2017). Results showed that forests and rangelands suffered from accelerated destruction during 1955– 2017 period. The reduction rate in areas of forests and rangelands were 87 and 147 ha/y. In contrast, the area of rain-fed agriculture and mixed land use (mixed of the forest- rangeland, and rangeland- rain-fed) that are more vulnerable to degradation hazard were increased by 500 ha per year. Rill and gully erosion features were obviously found in converted areas, especially in the rain-fed lands, indicating siltation and other environmental problems such as deforestation and carbon dioxide emission. In addition, irrigated lands were increased by 59.8 ha annually due to enhancing groundwater extraction through water well drilling. Currently, excessive water extraction has resulted in a negative balance of groundwater table leading to water scarcity in this area. The mix land use were found more vulnerable to soil erosion and deforestation problems.