Abstract:
The development of rainfall runoff relationship for ungauged watersheds using
topography, geomorphology and other regional information remains the most active area of
research in the field of hydrology. In the developing countries, some thumb rules and very old
equations are in practice for designing water resources structures which sometimes provide
erroneous results. In the proposed study, regional relationships have been developed for
computation of peak velocity and scale parameters of Nash model using geomorphological
and fluvial characteristics of 41 watersheds of varying characteristics in Central India region.
The regional relationships developed to determine scale parameter (k) of Nash model from a
morpho-fluvial factor, has facilitated derivation of at-site regional and regional only instantaneous
unit hydrograph (IUH), unit hydrograph (UH) and direct surface runoff (DSRO). The
performance of proposed regional model has been evaluated using spatial correlation coefficient,
integral square error, relative mean absolute error, root mean square error, relative error
in peak, coefficient of residual mass and model efficiency. The response of proposed regional
model have been found comparable with the observed values as the Nash-Sutcliffe efficiency
of proposed model during calibration varies from 69.7 % to 95.2 % for site specific approach,
60.6 % to 97.7 % for at-site regional and 67.1 % to 98.7 % for regional only approach.
Similarly, the performance of proposed model have been found satisfactorily during validation
as the efficiency varies from 81.3 % to 99.9 % for site specific approach, 83.5 % to 99.9 % for
at-site regional and 82.7 % to 99.9 % for regional only approach. The simple regional
relationships developed in the study can be used for event based rainfall-runoff modeling
and estimation of design flood in ungauged catchments of central Indian region.
