In this study, NASMO model, a rainfall-runoff method, which uses the SCS method to determine effective rainfall, the linear reservoir method to route the runoff over land and the modified Puls method to route the runoff in the stream have been applied for hydrological modeling of the Malaprabha catchment in Karnataka. Geographical Information Systems (GIS) has been applied to derive the catchment characteristics like shape, size, slope and land use pattern.
In hydrological analysis and design, precipitation-runoff relation is useful to extrapolate or interpolate runoff records from the precipitation records and to estimate the runoff of ungauged catchments. Estimates of hourly, daily, monthly, seasonal or annual runoffs may be required for operational purposes like efficient flood forecasting or to provide a database for evaluating reservoir storage requirements. Precipitation-runoff models are classified as lumped and distributed models. Lumped models are developed to get rough estimate of runoff peaks. However, distributed models can represent the complete catchment to get runoff hydrographs.
In the study, the parameter values were fitted for three rainfall storms and the corresponding hydrographs. As per the catchment characteristics, rainfall storms, corresponding runoff hydrograph, land use patterns and soil types, the best fitted parameters are in a reasonable range.
Based on the results, it can be concluded that the NASMO can be used to predict the runoff from Indian catchments. The error in the fitted parameter values will be reduced if more number of storms is used for parameter fitting. For effective use of this model for Indian catchments, complete details regarding land uses and soil conditions and channel characteristics of each sub-catchment are needed.
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