The study applies TOPMODEL (Topography Model) to the Malaprabha catchment of Krishna river basin in Karnataka to simulate the daily flows at Khanapur site. The catchment area of Malaprabha up to discharge measuring site Khanapur is 520 sqkm. The model uses topographic index for the formation of runoff through development of a Digital Elevation Model (DEM) by interpolating the contours in the basin at 300 m grid size.
The TOPMODEL is a variable contributing area conceptual model in which the predominant factors determining the formation of runoff are represented by the topography of the basin and a negative exponential law linking the transmissivity of the soil with the vertical distance from the ground level.
Though the TOPMODEL is a conceptual model, i.e., one in which the physical reality is represented, in a simplified manner, it is frequently described as being ‘physically based’, in the sense that its parameters can be measured directly in situ.
The results indicate that the model can be used to simulate the flows in the catchment quite accurately and its efficiency is 0.89 and 0.79 respectively in calibration and validation run. Also, the model is able to simulate the timing and magnitude of the peak flows satisfactorily.
The study suggests the need for an in-depth study to test and understand the use of different values for the sensitive parameters like decay factor (m) and transmissivity factor (To) for dry and wet seasons. Further, it is suggested that effect of land use change and morphology on the simulation of flows and the effect of DEM grid size on the simulation of runoff be studied.
It is suggested that the model be tested for the catchment using data for more number of years before concluding that the model can be used for any hydrological purposes.
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