Estimation of subsurface flow of hillslopes using of SCS and Nash models
Subject Areas : Article frome a thesisHossein Fariborzi 1 , TOURAJ SABZEVARI 2 , Reza Mohammad pour 3
1 - Department of Civil Engineering, Estahban Branch, Islamic Azad University, Estahban, Iran
2 - Department of Civil Engineering, Estahban Branch, Islamic Azad University, Estahban, Iran
3 - Department of Civil Engineering, Estahban Branch, Islamic Azad University, Estahban, Iran
Keywords: Rainfall simulator, SCS, NASH, Subsurface flow, Catchment,
Abstract :
Estimation of subsurface flow (SUF) is important in many catchments with good vegetation cover and high soil permeability and plays a major role in direct runoff. The concept of SUF in soil is still more complicated in comparison with surface flow, so providing predictive models for SUF basins with simple and practical methods are of interest to hydrologists. In this research, for the first time, surface rainfall-runoff models have been used to estimate the subsurface flow of the hillslopes. Two SCS and Nash models were used to estimate the subsurface of the catchments. In this paper, the unit hydrograph equations of the two models were considered as a function of the subsurface travel time and the amount of infiltration. Equations for calculating the actual SUF travel time were presented for use in models. To validate the results, results of rainfall simulator model were used to measure the surface and subsurface flow. The mean error in the surface runoff peak estimation was 7.8% and in the 6.7% subsurface runoff estimation by SCS model. In the meanwhile, the mean error in the peak runoff runoff estimation was 11.21% and in the subsurface runoff estimation was 11.32% in Nash method. The effect of slope and soil hydraulic conductivity on the SUF hydrograph were evaluated by two models.