Liu et al. (2026) Increased surface water evaporation loss induced by reservoir development on the Loess Plateau

Identification

• Journal: Hydrology and earth system sciences
• Year: 2026
• Date: 2026-01-09
• Authors: Yao Liu, Xianhong Xie, Yibing Wang, Arken Tursun, Dawei Peng, Xinran Wu, Baolin Xue
• DOI: 10.5194/hess-30-67-2026

Research Groups

• State Key Laboratory of Remote Sensing and Digital Earth, Faculty of Geographical Science, Beijing Normal University, Beijing, China
• Beijing Engineering Research Center for Global Land Remote Sensing Products, Faculty of Geographical Science, Beijing Normal University, Beijing, China
• Advanced Interdisciplinary Institute of Satellite Applications, Beijing Normal University, Beijing, China

Short Summary

This study investigates surface water evaporation losses on the Loess Plateau, China, from 2000-2018, using a modified Penman model and remote sensing data. It reveals that while evaporation rates slightly decreased, total evaporation volume significantly increased due to the expansion of small- and medium-sized reservoirs, highlighting a critical, often overlooked, water loss in regional water management.

Objective

• To estimate the spatial and temporal variability of surface water evaporation rates and volumes on the Loess Plateau.
• To identify the key driving factors underlying surface water evaporation losses.

Study Configuration

• Spatial Scale: Loess Plateau, China (approximately 640,000 km²). Evaporation rates and volumes computed and mapped at a 0.05° resolution.
• Temporal Scale: 2000–2018 (19 years), with monthly time steps for estimation and final results presented as average daily values.

Methodology and Data

• Models used:
  • Modified Penman equation (based on Zhao and Gao, 2019) incorporating dynamic water depth for heat storage estimation.
  • Novel water depth estimation algorithm based on slope equivalence between water body and boundaries.
• Data sources:
  • Remote sensing surface water area: Joint Research Center's Global Surface Water dataset (JRC-GSW, v1.6), 30 m spatial resolution, monthly.
  • Meteorological forcing: China Meteorological Forcing Dataset (CMFD, v1.6) (near-surface air temperature, specific humidity, downward surface shortwave radiation, wind speed), 0.1° spatial resolution, monthly.
  • Wind speed components (zonal and meridional): ECMWF Reanalysis 5th Generation (ERA5).
  • Elevation: Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTGTM), 30 m horizontal resolution, 1 m vertical resolution.
  • Open-water evaporation observations (for validation): China Meteorological Administration (CMA) pan evaporation data (E601 big pan, small pan), adjusted with pan coefficients (0.95 for E601, 0.75 for small pan).
  • In-situ water depth data (for validation): Global Reservoir and Dam dataset (GRanD).
  • Surface water withdrawal data: Yellow River Water Resources Bulletin (Yellow River Conservancy Commission, YRCC).

Main Results

• The modified Penman model with dynamic water depth showed robust performance against pan evaporation observations (average R² = 0.71, RMSE = 22.52 mm·month⁻¹, MAB = 18.85 mm·month⁻¹).
• The average open water evaporation rate on the Loess Plateau was 2.98 mm·d⁻¹ from 2000 to 2018, with a subtle, non-significant decreasing trend of -0.0031 mm·d⁻¹·yr⁻¹. Spatially, rates decreased from northwest (exceeding 5 mm·d⁻¹) to southeast.
• The total evaporation volume amounted to 4.16 × 10⁶ m³·d⁻¹ (2000-2018), exhibiting a significant upward trend of 0.117 × 10⁶ m³·d⁻¹·yr⁻¹. Total volume increased from 3.18 × 10⁶ m³·d⁻¹ in 2000 to 5.69 × 10⁶ m³·d⁻¹ in 2018.
• While the evaporation rate peaked in July and August, the evaporation volume showed seasonal peaks in May (6.04 × 10⁶ m³·d⁻¹) and October, primarily driven by seasonal fluctuations in water body areas.
• Attribution analysis revealed that the decreasing trend in evaporation rates was driven by a net balance of meteorological factors, with downward surface shortwave radiation (45.9%) and wind speed (37.8%) being dominant.
• The significant increase in total evaporation volume was overwhelmingly dominated by the expansion of surface water area (101.12% contribution), largely masking the modest net influence of meteorological factors (0.5%).
• The development of small- and medium-sized reservoirs and check dams was identified as the primary driver of increased evaporation losses, contrasting with a slight decrease in evaporation volume from large reservoirs.
• Total evaporation loss (approximately 1.55 × 10⁹ m³·yr⁻¹) was comparable to the average annual surface water withdrawal, with the ratio of evaporation loss to withdrawal escalating from 80% in 2000 to 130% in 2017.

Contributions

• Quantifies aquatic evaporation across the Loess Plateau, addressing a gap in previous studies that predominantly focused on non-aquatic terrestrial evaporation or only large water bodies.
• Introduces and validates a novel methodology that integrates remote sensing-derived dynamic water depth and surface area with a modified Penman model, enabling accurate regional evaporation estimation for numerous small-to-medium-sized water bodies where bathymetric data are typically unavailable.
• Reveals the paradoxical trend of decreasing evaporation rates but significantly increasing total evaporation volumes, attributing the latter primarily to anthropogenic expansion of surface water bodies, particularly small- and medium-sized reservoirs.
• Highlights the critical importance of evaporation losses, demonstrating they are comparable to surface water withdrawals, which has profound implications for sustainable water resource management and future hydraulic project planning in arid and semi-arid regions.

Funding

• National Key Research and Development Program of China (2024YFF1306302)
• National Natural Science Foundation of China (No. 42271021)

Citation

@article{Liu2026Increased,
  author = {Liu, Yao and Xie, Xianhong and Wang, Yibing and Tursun, Arken and Peng, Dawei and Wu, Xinran and Xue, Baolin},
  title = {Increased surface water evaporation loss induced by reservoir development on the Loess Plateau},
  journal = {Hydrology and earth system sciences},
  year = {2026},
  doi = {10.5194/hess-30-67-2026},
  url = {https://doi.org/10.5194/hess-30-67-2026}
}