Analysis and Evaluation of Land Use Changes in International Wetlands of Ala-Gol, Alma- Gol & Ajay-Gol In Turkaman Sahra, Using Multi-temporal Satellite Images Print

According to the Ramsar Convention, wetlands are areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six meters. According to recent estimations, world wetlands account for 6.2 to 7.6 percent of earth’s surface. To achieve the main objectives of the study, available TM and ETM satellite sensor imagery for 1987, 2000, 2005 and 2010 Alma gol, Aji gol and Ala gol international wetlands were selected. In preprocessing stage, after preparing the multi temporal images of region, radiometric, Geometric and normalization techniques were applied. In processing stage, the visual interpretation of images related to the study area and the reflective properties of water in the infrared band that is almost zero, the separation of land and water in the wetland area was identified. In addition to the visual methods, other digital image processing techniques like the ratio of bands, bands subtraction, and principal component analysis were used to identify areas of change. In post processing stage, the field survey and using GPS device in the study area with picking up required training samples the Envi software environment was applied to the MLC method. In the present study, with field survey and using GPS device and considering to the distribution of land covererage, six classes of usage in the areaof mentioned wetlands were selected as follows: Water, saltlands, arid lands, low vegetation density, average and high vegetation. It was attempted to regard distribution of sample areas in selecting training samples with overlapping training samples and creating false color composite images so that normal distribution of samples is obtained. Results show that during the research period (1987-2010) many changes in land use area has occurred which these changes include reduction in wetlands area from 2591.8 hectares in 1987 to 1280.6 hectares in 2010, reduction of salt lands, reduction in vegetation with high density, increase in vegetation with low/average density, and finally stability of thearid land area. The main causes of these changes should be explored in issues such as droughts, dam construction, extra wetlands water consumption in agriculture, fish farming and construction of canals and roads.