3 Results
3.1 Precipitation
We employed the Thiessen polygon method to determine the average precipitation across the study area. The Thiessen polygon method is considered more reliable and accurate than other methods for its ability to account for the uneven distribution of rainfall effectively. While the arithmetic mean method averages rainfall measurements from all stations, potentially overlooking extreme values, the Thiessen polygon method mitigates this issue by assigning weights to each station based on the area it represents. This approach ensures a more accurate reflection of average rainfall across the study area. (Faisal and Gaffar, 2012). The Thiessen polygon method creates a network of polygons around each rainfall station. The boundaries of these polygons are determined by drawing perpendicular bisectors between adjacent stations. The area of each polygon is then calculated and used to weigh the corresponding rainfall measurement. The weighted rainfall measurements were then summed together to obtain the average rainfall for the entire study area.
To utilize this approach in the Eskandari watershed, the initial step involved gathering data from 44 meteorological stations located within and around the watershed. Subsequently, ArcGIS software was employed to create a Thiessen polygon. Overlaying this network onto the study area divided the Eskandari Watershed into nine distinct regions, namely Eskandari, Ashann, Agche, Buin, Shafi al-Qassab, Fereydun Shahr, Qaleh-ye Baba Mohammad, Mirabad, and Meydanak stations. Figure \ref{871390} shows a DEM map of the Eskandari Watershed with the selected meteorological stations.