6.6-Sensitivity study of a distributed model for mountainous catchment

Abstract

In this paper, salient features of a distributed model capable of representing the spatially varied rainfall for a rain fed mountainous catchment are briefly described. It involves the development of isochronal map and then time area diagram for the catchment using information from toposheets,preferably in 1:50000 scale. The time of concentration is computed using Kirpich Formula involving determination of stream length and slopes for various sub-reaches of the river. The contours of equal time of travel are plotted on the map taking the time of interval same as that of the sampling interval of available rainfall-runoff records.

This model was applied for a typical case study for mountainous catchment of river Tons up to Kishau of area 4755 sq.km. In this study the results of sensitivity analysis of this model are presented so as to examine the effect on flood peak characteristics, magnitude as well as time due to variation in values of model parameters T and R. The effect on the objective c function,which was evaluated as sum of squares of the deviations between observed and computed runoff vaules, was also studied. This study indicates the effect of parameter uncertaintity on the design flood hydrograph characteristics as well as stability of parameter estimates. It has been observed from the study that the model output is more sensitive to the parameter, R,particularly when it is under predicted, in comparison to the parameter,T