Effects of Rainfall and Runoff Variables on Phosphorus Loss in a Forest Watershed, Iran

Suspended sediment resulted from distributed soil erosions facilitates nutrient transportation and influences soil depletion. Phosphorus (P) is one of the major limiting nutrients controlling eutrophication of surface water. Irregular P load pulsed by heavy rainfall may damage the ecological quality of downstream waters. P transport study during rainfall events is important in both predicting and controlling phosphorus loading in rivers. Therefore, evaluation of P erosion and transport processes in watershed scale is necessary for better understanding of the watershed system leading to appropriate management approaches. The present study was conducted in Kojour watershed, Iran to get some ideas about the effects of hyetograph and hydrograph variables on phosphorus loss and modeling of P loss. The results of modeling verified the better performance of multiple-variables regression equations due to use of the most important variables influencing on soil erosion and P transport, and estimating storm-wise P losses in the study area with an acceptable estimation error of some 23%.