Recalibration of a three-dimensional water quality model with a newly developed autocalibration toolkit (EFDC-ACT v1.0.0): how much improvement will be achieved with a wider hydrological variability?

Abstract. Autocalibration techniques have the potential to enhance efficiency and accuracy of intricate process-based hydrodynamic water quality models. In this study, we developed a new R-based autocalibration toolkit for Environmental Fluid Dynamics Code (EFDC) implemented it into recalibration Yuqiao Reservoir Water Quality Model (YRWQM), with long-term observations from 2006 2015, including dry, normal, wet years. The facilitated contributed exploring how model recalibrated performs more accurately robustly. Previously, original YRWQM was calibrated validated dry years in 2007, respectively. Compared YRWQM, performed just as well surface elevation, Kling–Gupta (KGE) 0.99, temperature, KGE 0.91, while performing better modeling total phosphorus (TP), chlorophyll (Chl a), dissolved oxygen (DO), KGEs 0.10, 0.30, 0.74, Furthermore, improved by 43 %–202 % TP–Chl a–DO process when compared models only overestimated DO concentrations, probably explained parameter algal growth rate that increased 84 %. poorly Chl a, due 50 reduction carbon-to-chlorophyll ratio, triggered changes composition population. Our study suggests calibrating may be an important measure improve robustness under severe hydrological variability. newly general automatic calibration possible hierarchical strategy will also powerful tool future complex calibration.