Assessment of climate change and its impacts on the natural land use of Gorgan river basin

The objective of this study is to investigate of climate change in Gorgan river-gharesoo basin and these impacts of this phenomenon on regional land use change، as well as provide guidance on the effective management and conservation of natural land area. Analysis of climate data including rainfall، average temperature and relative humidity of nine synoptic stations in this area from East to West، with a subscriber base of 30 years (1981 to 2011)، to examine the homogeneity of data and determine trends of changes in the time series of meteorological variables and calculation of the standardized precipitation index (SPI) based on rainfall recorded this time. In addition، to digitize maps of land use obtained from the cartography of the country (at two time) and convert into vector maps by ILWIS 3. 3 software، although، in order to analyze the land use maps، prepare the output maps and finaly compare of user specified percentage changes utilized by Arc GIS 9. 3 was used. Results indicated، during the study (30 years) the annual rainfall than central areas of the basin، has increased and rainfall could increase the occurrence of floods probe and be effective in this area. Based on seasonal temperature fluctuations، temperature changes in the eastern half of the rising and in the central and western parts declined. Also، changes of humidity in the eastern and the western parts of the basin were rising but the downward trends humidity scattered in different parts of this area. The annual average temperature and relative humidity of these regions have increased. Moreover، Findings from SPI indicated that almost in all stations of this basin، humidity has also improved and frequency of rainy and wet years of last two decades significantly has increased. In other words، changes in normal conditions of meteorological variables were climate changes actually and this phenomenon has occurred in Gorgan river-gharesoo basin. Results from output maps showed that changes during this period (10 years) have been reduced ranges and forests and have been increased agricultural and arid lands in this basin. Since the greatest changes in land use during this time period، converting more lands to agricultural land has been، thus، the population growth has been one of the most effective agents. Meanwhile، converting some lands to arid lands indicate that the effects of climate change on the land use change.