The accurate and precise calculation of the area for land features has a key role in the estimating the change detection of land uses and the classification of geomorphologic units as well as in the evaluating of land use. In particular, the delineation of borders between watersheds is a base in hydrologic analysis. Recent advances in spatial tools of GIS environment and the availability of various remotely-sensed data make the reliable determining of topographical boundaries possible. So an integrated approach of data analysis and modeling can accomplish the task of delineation. The main aim in this research is to evaluate the delineation method of watershed boundary by using four different digital elevation models (DEM) including ASTER, SRTM, Digital Topography, and Topographic maps. In order to determine a true reference of boundary of watershed, sample data were also obtained by field survey and using GPS. The comparison reference points and the results of these data showed the average distance difference between reference boundary and the result of ASTER data was 43 meters. However the average distance between GPS reference and the other data was high; the difference between the reference data and SRTM was 307m, and for Digital Topographic map, it was 269m. The average distance between Topographic map and the GPS points differed 304 meters as well. For the statistical analysis of comparison, the coordinates of 230 points were determined; the paired comparisons were also performed to measure the coefficient of determination, R-2, as well as the analysis of variance (ANOVA) in SPSS. As a result, the R-2 values for the ASTER data with the Digital Topography and Topographic map were 0.0157 and 0.171, respectively. The results showed that there were statistically significant differences in distances among the four means of the selected models. Therefore, considering other three methods, the ASTER DEM is the most suitable applicable data to delineate the borders of watersheds, especially in rugged terrains. In addition, the calculated flow directions of stream based on ASTER are close to natural tributaries as well as real positions of streams. [Hassan Ahmadi, Dr. Arun Das, Mehdi Pourtaheri, Dr. Chooghi Bairam Komaki, Houshang Khairy. Redefining the Border line of the Neka River's Watershed with Comparing ASTER, SRTM, Digital Topography DEM, and Topographic Map by GIS and Remote Sensing Techniques. Life Sci J 2012; 9(3):2061-]. (ISSN:1097-8135). http://www.lifesciencesite.com. 298
