Simulation of Runoff Quality in Sub-catchment of Karkheh Watershed Using a Field Rain Simulator

In this study, the effects of three land use categories on runoff quality was investigated using a rainfall simulator, in six sub-catchments in Kakasharaf watershed in Lorestan province. In total, 39 instances of artificial rain with a duration 30 min were created and the amount of phosphorus and potassium in the resulting runoff was measured on three land uses. The results showed that the average amount of phosphorus in runoff in forest, pasture and agriculture  land uses was respectively 0.22, 0.26 and 0.21 mg/kg. Also, the amount of potassium in runoff of forest, pasture and agriculture was respectively 18.38, 22.32 and 18.71mg/kg. Analysis of variance for the effect of land use on removal of phosphorus and potassium showed that the results were not statistically significant for phosphorous on slopes with 10% and 20% inclination and for potassium on a slope of 30% inclination. However, the effects of land use on the amount of potassium in runoff on slopes with 10% inclination was significant at the 95% confidence level.  On slopes with 20% inclination, the effect was significant at 99% confidence level.