Han et al. (2026) Combined evaporation estimation model of upper and lower reservoirs of pumped storage plants in arid areas under floating coverage

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2026
• Date: 2026-02-26
• Authors: Ke-Wu Han, Xian Cheng, Fei He, Kebin Shi, Xinjun Yan, Hai-Bo Jiang
• DOI: 10.1016/j.ejrh.2026.103281

Research Groups

• College of Hydraulic and Civil Engineering, Xinjiang Agricultural University, Urumqi, China
• Xinjiang Key Laboratory of Water Conservancy Engineering Safety and Water Disaster Prevention and Control, Urumqi, China
• School of Hydraulic and Ocean Engineering, Changsha University of Science & Technology, Changsha, China

Short Summary

This study developed and validated a combined evaporation estimation model for upper and lower reservoirs of pumped storage plants (PSP) in arid regions, accounting for unique operational conditions and floating ball coverage. The model demonstrated a significant water-saving effect of 61.2% at a 74% coverage rate, along with substantial energy and environmental benefits.

Objective

• To construct a calculation model for the combined water surface evaporation of the upper and lower reservoirs of pumped storage plants.
• To enable the constructed model to comprehensively characterize the influence of multiple parameters, including differentiated meteorological factors of the upper and lower reservoirs, mutual heat adjustment of water bodies, significant additional heat from friction, and physical properties of covering materials.
• To systematically explore the "water-energy" synergistic benefits of the model, specifically including water conservation effects and annual power savings from water replenishment pumps.

Study Configuration

• Spatial Scale: Arid region of northwest China, specifically near the Gaochang Pumped Storage Plant in Turpan City, Xinjiang. Field experiments were conducted on small circular evaporation ponds (1.0 m² area, 0.8 m depth).
• Temporal Scale: Field experiments and model simulations were conducted for the period from March to October. Annual benefits were calculated based on these findings.

Methodology and Data

• Models used:
  • A newly constructed combined water surface evaporation estimation model for upper and lower reservoirs, integrating energy balance, net radiation, latent heat flux, sensible heat flux, and a balanced temperature of the water column per unit area (Equations 1-15).
  • Wind function for large-area water surface (McJannet et al., 2012).
  • Benefit calculation models for power generation from water saved, saved electricity from water pump supply, and carbon dioxide emission reduction (Equations 21-23).
  • Statistical metrics: Root Mean Square Error (RMSE), Index of Agreement (D), and Mean Bias Error (MBE) for model validation.
• Data sources:
  • Field experiments on evaporation inhibition rate of small evaporation ponds covered by high-density polyethylene (HDPE) floating balls (100 mm diameter, 74% coverage rate) near the Gaochang PSP.
  • Measured meteorological parameters (air temperature, floating ball surface temperature, solar shortwave radiation, wind speed, relative humidity) and evaporation from the ponds.
  • Basic operational parameters of the Gaochang PSP (rated head, storage capacity, water level fluctuation, water depth, surface area, water supply source height difference, efficiencies).
  • Meteorological parameters for the Gaochang PSP, including atmospheric temperature and wind speed for both upper and lower reservoirs, with upper reservoir parameters adjusted based on altitude difference.
  • Environmental Impact Assessment Report of Gaochang PSP Station.
  • China Electricity Council, Annual development report of China's electricity industry 2020.

Main Results

• At a floating ball coverage rate of 74%, the water-saving effect of the reservoirs reached 61.2%.
• The constructed model showed good simulation performance, with RMSE of 0.23 mm/d, D of 0.99, and MBE of 0.99 against field observations for small evaporation ponds. For overall model performance verification, MAE was 0.03, RMSE was 0.04, and MBE was 0.01.
• Additional heat from PSP operation significantly increased water temperature, averaging 1.85 ℃ per month under uncovered conditions and 4.31 ℃ per month under covered conditions from March to October.
• Floating ball coverage significantly reduced the water temperature decrease rate in autumn/winter, inhibiting water freezing. From August to October, the water temperature decrease rate changed from 4.54 ℃/month to 1.94 ℃/month (without additional heat) and from 4.30 ℃/month to 1.20 ℃/month (with additional heat).
• For a typical PSP in cold and arid regions with 74% floating ball coverage (considering additional heat):
  • Annual water saved by evaporation prevention: 556,700 m³.
  • Annual power generation potential from water saved: 682,600 kW⋅h.
  • Annual electricity saved by water replenishment pumps: 1,213,500 kW⋅h.
  • Additional carbon emission reduction: 1589 t per year.
  • Annual operational cost savings: 5.67 million CNY, with an investment payback period of 5.45 years.

Contributions

• Developed the first combined evaporation calculation model specifically for the unique operating conditions of upper and lower reservoirs of pumped storage plants, addressing a critical research gap.
• The model uniquely integrates complex factors such as differentiated meteorological conditions, mutual heat exchange between reservoirs, frictional heating from PSP equipment, and physical properties of covering materials.
• Quantified the multi-faceted "water-energy-ecology" synergistic benefits of floating ball coverage, including water conservation, increased power generation, reduced pumping energy consumption, carbon emission reduction, and prolonged winter operation.
• Provides a practical and quantitative reference for the planning, design, and safe operation of pumped storage plants in arid regions, especially concerning water resource management and climate change adaptation.

Funding

• National Natural Science Foundation of China (52469005)
• Hunan Provincial Department of Education Young Scholars Fund (22B0309)
• Xinjiang Key Laboratory of Water Conservancy Engineering Safety and Water Disaster Prevention and Control (ZDSYS-JS-2024–01)

Citation

@article{Han2026Combined,
  author = {Han, Ke-Wu and Cheng, Xian and He, Fei and Shi, Kebin and Yan, Xinjun and Jiang, Hai-Bo},
  title = {Combined evaporation estimation model of upper and lower reservoirs of pumped storage plants in arid areas under floating coverage},
  journal = {Journal of Hydrology Regional Studies},
  year = {2026},
  doi = {10.1016/j.ejrh.2026.103281},
  url = {https://doi.org/10.1016/j.ejrh.2026.103281}
}