TR(BR)-3/99-2000 : Application of SCS-CN based runoff model

Abstract

Modelling of rainfall generated runoff is of paramount importance in hydrological design of water resources structures. The Soil Conservation Service (1956, 1964, 1985) Curve Number (SCS-CN) method is most popularly used by scientists, engineers, practitioners, and academicians, for it is simple, stable, and takes into account most of the watershed's runoff producing characteristics: soil type, land use, hydrologic condition, and antecedent moisture condition. This event-based spatially and temporally lumped method has also been used in long term hydrologic simulation with varying degree of success. The present report develops a spatially lumped but temporally distributed SCSCN based runoff model for simulating seventeen rainfall-runoff events of a mine-affected Himalayan Jhandoo Nala watershed (area=17.7 ha) and seven events of 3F sub-zone watershed (area = 823.62 sq. km) of Godavari. The application of the developed methodology has also been demonstrated with the help of two examples. Simulation results are discussed with the help of error criteria of standard error and coefficient of determination, for evaluating the model performance, and relative error is used for evaluating the model performance in simulating the volumes of the runoffs. It is found that peak discharges and time to peak discharges simulate reasonably well and mass is conserved satisfactorily.