Zhang et al. (2025) Irrigation cooling effect reduced by water-saving practices

Identification

• Journal: Communications Earth & Environment
• Year: 2025
• Date: 2025-12-03
• Authors: Chao Zhang, Quansheng Ge, Wim Thiery, Yan Li, Shushi Peng, Guoyong Leng, Guosong Zhao, Zhenong Jin, Wei Li, Kun Zhang, Xuezhen Zhang, Songjun Han, Geli Zhang, Xiangming Xiao, Jinwei Dong
• DOI: 10.1038/s43247-025-03030-5

Research Groups

• Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
• University of Chinese Academy of Sciences, Beijing, China
• Department of Hydrology and Hydraulic Engineering, Vrije Universiteit Brussel, Brussels, Belgium
• State Key Laboratory of Earth Surface Processes and Resources Ecology, Beijing Normal University, Beijing, China
• Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing, China
• Hubei Key Laboratory of Regional Ecology and Environmental Change, School of Geography and Information Engineering, China University of Geosciences, Wuhan, China
• Institute of Ecology, College of Urban and Environmental Science, Peking University, Beijing, China
• Department of Earth System Science, Ministry of Education Key Laboratory for Earth System Modeling, Institute for Global Change Studies, Tsinghua University, Beijing, China
• School of Geospatial Engineering and Science, Sun Yat-Sen University, Zhuhai, China
• State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing, China
• College of Land Science and Technology, China Agricultural University, Beijing, China
• Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, USA

Short Summary

This study reveals that the widespread adoption of water-saving irrigation (WSI) practices across China has significantly weakened irrigation's daytime cooling effect on land surface temperature while intensifying nighttime cooling, driven by shifts in surface energy partitioning.

Objective

• To provide the first large-scale observational assessment of how water-saving irrigation (WSI) alters irrigation-induced climatic effects across China.
• To test the hypothesis that widespread WSI implementation has attenuated irrigation's cooling effect, contributing to regional warming.
• To test the hypothesis that the direction and magnitude of these effects vary across space and time, depending on WSI intensity and local climatic conditions.

Study Configuration

• Spatial Scale: National (China), climate zones (arid, semi-arid/humid, humid), provincial, and 1-kilometer pixel resolution.
• Temporal Scale: Two decades (2001–2020), annual, seasonal, and diurnal.

Methodology and Data

• Models used:
  • Penman-Monteith–Leuning V2 (PML_V2) for evapotranspiration partitioning.
  • Multiple linear regression for attribution analysis.
  • Structural equation modeling (SEM) for causal pathway analysis.
• Data sources:
  • Satellite observations: MODIS (MOD11A2 for LST, MCD43A3 for albedo, MOD13A2 for EVI).
  • Irrigation datasets: IrriMapCN (500-meter annual time-series, 2000–2019), IrriMapMeier (1999–2012).
  • Land cover data: National Land Cover Dataset of China (NLCD-China).
  • Water use data: China Water Resources Bulletin (2003–2020) for per-hectare irrigation water use (IWU).
  • Climate reanalysis: TerraClimate (monthly, 4-kilometer resolution for air temperature, precipitation, wind speed, downward shortwave radiation), FLDAS for downward longwave radiation.
  • Topography: Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) at 1-kilometer resolution.

Main Results

• Per-hectare irrigation water use (IWU) in China declined by over 30% from 2001 to 2020.
• Daytime land surface cooling weakened by 0.05 K per decade nationally (15% relative to the 20-year mean), with the largest weakening (0.20 K per decade, 9%) observed in arid regions.
• Nighttime land surface cooling intensified by 0.04 K per decade nationally, most prominently in arid zones (−0.09 K per decade).
• The weakening of daytime cooling is primarily driven by a shift in surface energy partitioning, with an increased sensible heat flux (rising Bowen ratio) outweighing latent heat flux.
• The intensification of nighttime cooling is attributed to reduced soil moisture (leading to lower soil thermal capacity) and enhanced radiative feedbacks.
• Declining IWU was the dominant driver of these ∆LST trends, explaining 77% of the variance in daytime ∆LST trends and 87% of nighttime ∆LST trends nationally.
• Vegetation greening partially offset daytime warming in semi-arid and semi-humid regions by sustaining transpiration, but was insufficient to fully compensate for the reduced latent heat under lower water inputs.

Contributions

• Provides the first large-scale observational assessment of how water-saving irrigation (WSI) alters irrigation-induced climatic effects, specifically focusing on China.
• Reveals a country-scale pattern of WSI's impact on land surface temperature (LST), moving beyond regional or small-scale studies.
• Uncovers contrasting diurnal trends in irrigation-induced cooling effects (weakened daytime, intensified nighttime), a dimension rarely addressed previously.
• Offers an integrative analysis of the underlying mechanisms, including shifts in surface energy partitioning driven by the competing influences of crop greening and reduced irrigation water use.
• Highlights an emerging trade-off between water-use efficiency and climate mitigation, underscoring the urgent need for Earth system models and climate change projections to incorporate evolving irrigation practices.

Funding

• Strategic Priority Research Program of the Chinese Academy of Sciences (Grant Nos. XDA23100400, XDA28060100)
• CAS Youth Interdisciplinary Team Project (Grant No. JCTD-2021-04)
• National Natural Science Foundation of China (Grant Nos. 41871349, 42271375)
• US National Science Foundation (Grant Nos. 1911955, 1946093)

Citation

@article{Zhang2025Irrigation,
  author = {Zhang, Chao and Ge, Quansheng and Thiery, Wim and Li, Yan and Peng, Shushi and Leng, Guoyong and Zhao, Guosong and Jin, Zhenong and Li, Wei and Zhang, Kun and Zhang, Xuezhen and Han, Songjun and Zhang, Geli and Xiao, Xiangming and Dong, Jinwei},
  title = {Irrigation cooling effect reduced by water-saving practices},
  journal = {Communications Earth & Environment},
  year = {2025},
  doi = {10.1038/s43247-025-03030-5},
  url = {https://doi.org/10.1038/s43247-025-03030-5}
}