SURFACE HYDROLOGICAL. APPRAISAL OF UPPER MAHANADI BASIN

Abstract

A detailed rain-fall runoff study pertaining to Upper Mahanadi basin was taken up with the view to compute floods using various hydrological approaches such as Sherman's unit hydrograph approach, Nash's conceptual modeling approach and a event based distributed modeling approach. Average 1-day unit hydrographs were developed from the available rainfall-runoff records for all sub-basins of the study area using Sherman's unit hydrograph theory as well as Nash's conceptual model. Subsequently flood hydrographs for various storm events for different sub-basins were computed using these average 1-day unit hydrographs respectively. Usually the occurrence of the rainfall is highly non-uniform in time and space domains. Many of the usual rainfall-runoff modeling techniques like Sherman's unit hydrograph approach, Nash's conceptual modeling approach or other. simpler lumped conceptual models are not capable of representing the spatial variability in the rainfall pattern. Therefore, a event based distributed rainfall-runoff model, which accounts for the spatial and temporal rainfall variability within the catchment under consideration is developed. The model is basically based on the time-area concept for computing the direct runoff at the outlet of the catchment under consideration. The model is calibrated and tested for some of the sub-basins of Upper Mahanadi basin using the available limited data on rainfall and runoff.