**7. Climate**

to

31" north latitude, having an area of 223000

Sarab Drainage Basin is located in the extreme northeast part of Gorganrood Catchment. For investigating climatic conditions of the studied area, statistical data of stations within and around the basin were used. After controlling and completion of the data, statistical period was chosen from 1971 to 2002 in which most of the stations had data. The highest mean monthly precipitation of basin is from March which is 65 millimeters and the lowest from July which is 14 millimeters. Winter season is with the highest amount and summer season

Investigation of Effective Factors on Runoff Generation and

Consultant Engineering Co., 1996)

Management, 2007)

Sediment Yield of Loess Deposits Using Rainfall Simulator 121

Fig. 3. Climatic classification map of Sarab Drainage Basin using Domarten Index (Jamab

Fig. 4. Intensity-Duration-Frequency curves of Tamer Station (Golestan Province Watershed

with the lowest amount of precipitation. Also evapotranspiration potentials of the basin vary from 880 to 990 millimeters in year.

Fig. 2. Map of elevation of Sarab Drainage Basin

Considering the existing data, two methods of Domarten and Amberge climatic classifications were used. Figure 3 shows climatic classification of Sarab Drainage Basin which is prepared using climatic classification of Gorganrood Catchment (Jamab Consulting Engineering Co., 1996) and was corrected later on (Golestan Province Watershed Management, 2007). Vegetation and geomorphological conditions of the area confirm this classification.

For studying the intensity and the amount of precipitation in different time periods, statistical data of climatic station of Tamer Village which belongs to Ministry of Energy, is located in the studied area and has suitable statistical data(suitable quality and duration of data) was used. Figure 4 shows Intensity-Duration-Frequency curves of this station.
