Investigating the Landuse and Local Climate Changes in Gavehrod Basin before and after Gavoshan Dam Construction

Dam construction in a watershed causes changes in basin’s entire land cover and landuse. These changes affect basin’s local climate and governed natural process directly or indirectly. In this research, the trend of vegetation land cover and land surface temperature changes for the period of before and after Gavoshan dam construction in Gavehrood basin was studied using temporal Landsat images. To obtain vegetation cover changes, NDVI, EVI and SAVI indices were used. They all show an increase in vegetation cover in the south of dam. To obtain LST and LSE, Planck equation and NDVI thresh holding method used respectively. Analysis of spatial variations of temperature classes from land surface emissivity show that Downward the dam of very warm temperature category are eliminated and cool and very cool temperature categories replaced instead. Analysis of NDVI index show it has been changed averages from 0.13 to 0.165. So, changes in other vegetation indices have been incremental. With production of normalized classes of Temperature was determined that area of average class increased about 67 Km2 (7.3%) and area of very warm class about 11 Km2 (17.5%) decreased. Analysis the dispersion diagram of temperature normalized and vegetation (Fr/T) shows in the course of study decreased the dry edge length and increased the wet edge length. This means that the existence of water surface in this Basin in addition to changing vegetation coverage and soil moisture causes land surface temperature change which in turn evolves the microclimate of the region in the long term.