CS(AR)-3/96-97 : Daily rainfall-runoff modelling of Brahmani river at rengali reservoir

Abstract

A hydrologic simulation model, HYSIM has been applied to Brahmani river basin for modelling the daily flows of the river at Rengali reservoir. Keeping in view the large catchment area of 25,250 sq.km. at Rengali reservoir, the basin for the modelling purpose has been divided into two sub-basins viz, upper sub-basin and lower sub-basin. The upper sub-basin having a catchment area of 16,900 sq.km. upto Bolani gauging site is treated as a nominal sub-basin since the daily flows from this sub-basin as recorded at Bolani gauging site are available. The lower sub basin below Bolani and upto the reservoir with its catchment area of 5,350 sq.km. is simulated for daily flows. The recorded flows from the upper sub-basin are routed through the lower sub-basin along with the flows from local runoff from the lower sub-basin to the reservoir site. The model is calibrated using 3 years of data and is validated for its performance for a set of next 3 years of data.

The results of the simulation study are quite encouraging. The model has reproduced the peaks and the shape of the hydrographs reasonably accurate despite the constraints that the PET values used in the study are normal monthly values and secondly, the flows at Rengali reservoir as used for comparison purpose arc the average daily reservoir inflows computed from the reservoir capacity curves. From the analysis of the results, it is concluded that the model can be effectively used for forecasting of flows at Rengali reservoir which will be useful for planned regulation of the reservoir storage during high flow periods.