Investigate the Potential of Runoff in Small Watershed (Case Study: Sanganeh Kalat Watershed)

Determination of threshold runoff is very important since it helps us estimate and design flood and runoff potential، and has an important roleinthe optimal use of precipitation. In this study، rainfall and runoff events were measured in the SanganehKalat watershed during the years 2008 to 2011. Precipitation using a rain gauge and runoff was recorded with five water level gauges four of whichwere installed at the outlet of the sub watershed and one of whichwas installed at the outlet of the main watershed. A total of 128 events were recorded 8 of which generated runoff. According to the defined threshold runoff،some of the precipitation which increases surface soil moisture until runoff is generated، showed that the lowest threshold runoff in the sub watershed is about 1 mm and in the main watershed is about 2. 2 mm. Hence، study of single rainfall event is very important and considering a part of the monthly cumulativeand annual rainfall as runoff is associated with a high error. Runoff volume during the project shows that according to the physiographic factors، soil and vegetation cover of the sub watersheds، the potential of runoff generation is different. Based on the results of this study، according to the area of the sub watershed، the potential of runoff generation in sub watersheds A1 to A4 and S are 116، 11، 26، 28 and 25 cubic meters per hectare per year، respectively.