Development of Geomorphology Based Regional Nash Model for Data Scares Central India Region

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.