The purpose of this study is to determine the run off coefficient in Kissilian Basin. On the basis of of USDA methodology surface run off can be evalueted if environmental factors like soil physical properties vegetative cover and land use planning is considered. In this study required data for the surface run off in the area was collected and finnally observed CN and run off curve number in Soil Conservation Service method was calculated and reported in this paper. Some studies such as physiography, meteorology, hydrology , soil characteristics, geology , vegetative cover and land use have been conducted to get essential information. The results of the studies indicated a CN value of 72.5 for the Kissilian Basin. Statistical analysis has shown that there is a logical correlation between the rate of precipitation and the height of run off and peak discharge. Also , the curve number has shown excellent correlation between the rate of precipitation and the relative of the five anticident moisture days. The selected curve number (CN II) based Offbasin characteristic has shown an excellent correlation between the rate of precipitation, height of run off, peak discharge and the relative humidity of the anticident moisture. The estimation of peak discharge by computation which is determined by curve number method is suitable method for Kissilian basin
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