Assessing streamflow modeling using single and multi-site calibration approach on Bharathpuzha catchment, India: a case study

A vital challenge of assessing global water resources is to achieve the optimal set of parameters in any hydrological model by simulating streamflow. Simulating single-site hydrological features for a large catchment may not account for regional variation, resulting in unmet watershed needs. The objective of this study was to assess the single-site calibration (SSC) and multi-site calibration (MSC) approaches using the hydrological Soil and Water Assessment Tool (SWAT) model on the Bharathpuzha watershed of India. The multi-site method entails splitting a large catchment into smaller ones and applying MSC criteria to the entire catchment. Monthly streamflow simulations were conducted to verify the model’s performance using the coefficient of determination ( R 2 ), Nash–Sutcliffe Efficiency (NSE), percent of bias (PBIAS) and Kling Gupta Efficiency (KGE). Results show that single-site approach values are more meaningful than multi-site. In SSC, the parameter determined by optimizing the model parameters at four different stations delivers a better result than in MSC, and MSC has less uncertainty with lower PBIAS and r-factor values. This case study was assumed to give experience with single and multi-site calibration in a large catchment and reveal the positives and negatives of SSC and MSC estimated parameters.