Rainfall Runoff Model Development Under Regulated River Flow Condition

Abstract

Observed discharge is one the crucial and common input parameter required in rainfall runoff model development and importantly, it should be the true representative runoff of that river basin. When the stream flow regime is regulated, it needs to be modified or corrected before setting up the rainfall runoff models. To examine the fact, the study was carried out in the Kharun river, a tributary of Seonath river in Chhattisgarh state having strongly regulated flow regime. The non-regulated flow time series at Patherdihi was simulated from the regulated observed flow at Patherdihi G/D site by developing Kharun river basin model in Mike Basin software using the information on storages, addition, diversion and return flows from irrigation, etc. The MIKE 11 NAM rainfall runoff models were developed under regulated flow condition and non-regulated (virgin) flow conditions. Accuracy of the models were examined on the basis of coefficient of determination (R2), Efficiency Index (EI), Sum of Square of Error (SSE) and percentage difference between observed and simulated discharge. When the model was developed under non-regulated condition, the R2 value increased from 0.78 to 0.858, Efficiency Index increased from 0.71 to 0.86 and the difference between observed and simulated discharge reduced from 6.2 to 3.5% and the SSE of the model was found reduced by 25% indicating improved agreement between simulated and observed runoff. The model accuracy was seen higher when the model was developed using the non-regulated flow data. It could be concluded that the rainfall runoff model simulation using regulated flow data as an input may lead to inaccurate simulation of river flow.