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 (R2), 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.