Long term hydrologic simulation using SCS-CN method - A research report by National Institute of Hydrology

The report uses the Soil Conservation Services (SCS, 1956), Curve Number (SCS-CN) method, for simulating daily rainfall-runoff data of three catchments, viz., Ramganga, Hemavathi and Sabarmati.

The report uses the Soil Conservation Services (SCS, 1956), Curve Number (SCS-CN) method, a widely used event based rainfall-runoff method for simulating daily rainfall-runoff data of three catchments, viz., Ramganga and Hemavathi catchments of the sub-humid regions and Sabarmati catchment of the arid region of India.

In the model formulation, the daily variation of parameter, potential maximum retention is governed by the known antecedent moisture condition. Hydrologic simulation studies provide a useful and important input to water resources planning and watershed management practices.

Simulation of Ramganga data is performed using data in its primitive form as well as the data perturbed about seasonal means, identified as Case A and Case B, respectively. The usage of perturbed data in Case B parallels the concept of linear perturbation model (LPM).

The simulation results of Case B exhibit better performance than those of Case A as well as the results of the LPM, for the validation period of 6 years. The Case A results exhibit efficiency of 50.073 % in calibration and 67.299 % in validation in Ramganga application, 72.444 % in calibration and 75.567 % in validation in Sabarmati application.

Thus, the simulation model has exhibited better performance on the catchments falling in the sub-humid region as compared to that falling in the arid region. A sensitivity analysis of the model is also performed on the Hemavathi catchment data used in validation. The parameters CN, d1, d2, d3, d4 are found to be more sensitive than gamma, NLAG and bf and therefore, require careful estimation for field application.

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