COMPARISON OF A NEW GIS‐BASED METHOD AND A MANUAL METHOD FOR DETERMINING BOUNDERY BASIN: ZAYANDEH ROOD BASIN IN IRAN

Hydrologic modeling is one of many useful applications of Geographic Information Systems (GIS). Elevation data in a grid format can be used to delineate drainage basins, create stream Networks, and compute drainage basin data. (Christopher M. Smemoe1997, E. James Nelson1994). By digital elevation data and SRTM; it is simple to delineate boundary basins. This paper focuses on using a hydrologic model in a GIS as determining boundary of basin and to compare with hand drawing boundary of basin. In this paper, we used the Arc Info Workstation component of Arc GIS 9.3 Software and were used some data, included: SRTM and 1:25000 topographic maps with a contour interval of 25 meters. The study area for this investigation, chosen for its one of large basin in center of Iran, included about 42,000 km2. Differences between the determination boundaries basins derived from the two methods for the basin were useable. The study found that to determine exact boundaries of basin on contour maps is limited by map scale and contour interval. Gathering and analyzing basin data for studies in mature regions has historically required the tedious, time‐consuming process of manually boundary of basin shown on topographic maps. By these results: 1) to get an exact boundary of basin by GIS method. 2) Saving time for gathering data and doing work by GIS method. 3) The map is more benefit for analyzing in order to other purposes.4) it is some deference between close basin and open basin.