Operating-Spectrum Optimization of Water-Intake Pump Retrofits Under Hydrological Variability: Integrating Hydraulic Performance, Energy Use, and Carbon Cost

A pump selected at one duty point may perform poorly over a full year because river level, pipe resistance, demand, and the number of running units all change the operating point. This paper compares discrete retrofit options for a water-intake pumping station using a documented steady-state hydraulic model, pump performance surfaces, and a representative hydrological year (RHY). The analysis distinguishes field observations from engineering calculations, reconstructed operation, and economic scenarios. Two pre-retrofit DCS snapshots give back-calculated pump hydraulic efficiencies of 73% and 65%. These values cannot be compared directly with the 87.8% factory efficiency because the operating conditions and test boundaries differ. The RHY comprises 35,136 modelled 15 min intervals and is not presented as measured SCADA. Using the engineering-record estimate of a 40 kW reduction per active pump, annual electricity use falls from 3232.2 to 2398.7 MWh, corresponding to 833.6 MWh (25.8%) of modelled savings. A 30–50 kW sensitivity range gives savings of 625.3–1042.1 MWh (20.7–30.3%). The redesigned pump has a reconstructed mean hydraulic efficiency of 86.72%, and 93.3% of delivered volume is conveyed at efficiencies above 86%. In the anonymous life-cycle screen, the retained-interface redesign has the lowest central cost at 62.36 RMB/t CO2, while deeper replacement becomes competitive only at higher shadow carbon prices. The findings show the value of matching a retrofit to the annual operating spectrum, although full-year field data are still needed to verify the predicted savings.