The present study aimed to investigate the annual potential of water hyacinth (WH; Eichhornia crassipes) macrophyte in an un-operated/abandoned stretch of the upper Ganga canal at Haridwar, India. The study covered a 25 km long and 100 m wide stretch of the old Ganga canal which exhibits a huge WH growth every year. For this, standard field and laboratory methods were adopted to estimate the WH biomass density (Kg/m²), and heavy metals dynamics between canal water and macrophyte biomass. Results showed that the average annual density of WH biomass was 5.538 kg/m² with significant (P < 0.05) heavy metals (HMs) accumulation as 1.50 mg/Kg dw of Cd, 0.21 of mg/Kg dw of Cr, 2.19 mg/Kg dw of Cu, 28.54 mg/Kg dw of Fe, 20.79 mg/Kg dw of Mn, and 9.39 mg/Kg dw of Zn, respectively. Using a polynomial cubic model, the annual trends of WH growth and HMs accumulation in both water and biomass were also simulated. The developed models showed good R² and error validation results that support the prediction criteria. The findings of this study revealed that WH’s growth in the un-operated stretch of the old Ganga canal located at Haridwar has high HMs accumulation and biomass production potentials.