Yang et al. (2025) Increasing irrigation water requirements across croplands in the Contiguous United States throughout the 21st century

Identification

• Journal: Agricultural Water Management
• Year: 2025
• Date: 2025-12-03
• Authors: Haoxuan Yang, Jia Yang, Tyson E. Ochsner, Quan Zhang, Xiaohao Jiao, Shanmin Fang, Yuting Zhou, Chris B. Zou
• DOI: 10.1016/j.agwat.2025.110044

Research Groups

• Department of Natural Resource Ecology and Management, Oklahoma State University, Stillwater, OK, USA
• Department of Plant and Soil Sciences, Oklahoma State University, Stillwater, OK, USA
• Department of Geography, Oklahoma State University, Stillwater, OK, USA

Short Summary

This study estimates crop-specific irrigation water requirements (IWR) across the Contiguous United States (CONUS) throughout the 21st century under moderate (SSP245) and severe (SSP585) warming scenarios. Results project a continuous increase in IWR across CONUS, with annual average IWR depth rising by 10.3 % under SSP245 and 26.4 % under SSP585 by the late 21st century, highlighting growing challenges for agricultural water management.

Objective

• To estimate irrigation water requirements (IWR) for ten major field crops in the Contiguous United States (CONUS) by accounting for their phenology and growth cycles.
• To characterize the spatial patterns and temporal trends of future IWR across the CONUS under projected climate change scenarios.
• To identify the drivers of IWR changes and provide suggestions to sustain long-term agricultural production.

Study Configuration

• Spatial Scale: Contiguous United States (CONUS), analyzed at a 25 km spatial resolution and delineated into seven National Climate Assessment (NCA) regions.
• Temporal Scale: 21st century (2000–2099), with analysis focused on three 20-year periods: early (2000–2019), middle (2040–2059), and late (2080–2099).

Methodology and Data

• Models used:
  • Irrigation Water Requirement (IWR) estimation: Smith (1992) model, adapted by Döll and Siebert (2002), incorporating crop coefficients (Kc) and effective precipitation (Peff). For rice, additional percolation losses were included.
  • Reference Evapotranspiration (ET0): FAO56 Penman-Monteith equation.
  • Effective Precipitation (Peff): Empirical relationship by Smith (1992).
• Data sources:
  • Climate projections: Coupled Model Intercomparison Project Phase 6 (CMIP6) from five General Circulation Models (GCMs): CanESM5, EC-Earth3, GFDL-ESM4, MIROC-ES2L, and MPI-ESM1–2-HR.
  • Downscaled climate data: NEX-GDDP-CMIP6 dataset (0.25° spatial resolution, resampled to 25 km) for near-surface specific humidity, precipitation, surface downwelling shortwave radiation, daily-mean near-surface wind speed, and daily maximum/minimum near-surface air temperature.
  • Climate scenarios: Shared Socioeconomic Pathways (SSP245 - moderate warming, SSP585 - severe warming).
  • Elevation data: NASA Shuttle Radar Topography Mission (SRTM) Digital Elevation Models (DEM) at 30 m resolution, resampled to 25 km.
  • Crop types and distribution: Cropland Data Layer from USDA National Agricultural Statistics Service (NASS) at 30 m resolution (2009 reference year), used to calculate fractional coverage of ten major field crops (alfalfa, barley, corn, cotton, peanuts, rice, sorghum, soybean, spring wheat, winter wheat) within 25 km pixels.
  • Crop growth period and phenology: USDA state-level usual field crops data.
  • Soil drainage class: Soil Survey Geographic Database (SSURGO), resampled to 25 km.

Main Results

• Annual average IWR depth across CONUS is projected to continuously increase throughout the 21st century.
  • Under SSP245, IWR depth increases from 366.5 mm yr⁻¹ (2000–2019) to 404.4 mm yr⁻¹ (2080–2099), a 10.3 % increase.
  • Under SSP585, IWR depth increases from 366.2 mm yr⁻¹ (2000–2019) to 462.7 mm yr⁻¹ (2080–2099), a 26.4 % increase.
• Each 1 °C increase in annual temperature is associated with a 4.2–5.0 % (15.1–18.1 mm yr⁻¹) increase in IWR across CONUS croplands.
• Monthly IWR peaks in July, reaching 95.7 mm month⁻¹ under SSP245 and 105.8 mm month⁻¹ under SSP585 in the late 21st century.
• Crop-specific IWR: Rice has the highest average IWR per unit cropland area (e.g., 1017.3 mm yr⁻¹ under SSP585 late century), followed by alfalfa and cotton. Soybean shows the highest percentage increase under SSP585 (44.9 %). Winter wheat is the most climate-sensitive crop, with an 8.0 % increase in IWR per 1 °C warming.
• Regional IWR:
  • The Southern Great Plains and the Midwest exhibit the highest total IWR amounts (e.g., Southern Great Plains: 105.0 billion m³ yr⁻¹ under SSP245 and 120.1 billion m³ yr⁻¹ under SSP585 in the late century).
  • The Southwest region has the highest IWR depth per unit cropland area (e.g., 739.6 mm yr⁻¹ under SSP245 and 790.6 mm yr⁻¹ under SSP585 in the late century).
• Changes in crop growth period significantly impact IWR: shortening the growth period by 30 days reduces IWR by approximately 14 %, while extending it by 30 days increases IWR by about 8 %.

Contributions

• Provides the first national-level estimates of future irrigation water requirements (IWR) for ten major field crops across the Contiguous United States (CONUS) under CMIP6 climate change scenarios (SSP245 and SSP585), filling a critical knowledge gap.
• Incorporates crop-specific phenology and growth cycles into IWR estimations, enhancing accuracy for diverse agricultural systems.
• Quantifies the spatial patterns and temporal trends of IWR changes throughout the 21st century, offering detailed insights into regional and crop-specific vulnerabilities.
• Establishes a quantitative relationship between temperature increase and IWR, providing a key metric for climate change impact assessment.
• Proposes actionable adaptation strategies, such as optimizing crop structure, developing shorter-duration cultivars, and reallocating crops to water-abundant regions, to enhance water sustainability in agriculture.

Funding

• Geological Survey South Central Climate Adaptation Science Center grant (G23AC0454)
• National Science Foundation Oklahoma EPSCoR S3OK project (Grant No. OIA-1946093)
• National Science Foundation Rural Confluence project (No. 2316366)

Citation

@article{Yang2025Increasing,
  author = {Yang, Haoxuan and Yang, Jia and Ochsner, Tyson E. and Zhang, Quan and Jiao, Xiaohao and Fang, Shanmin and Zhou, Yuting and Zou, Chris B.},
  title = {Increasing irrigation water requirements across croplands in the Contiguous United States throughout the 21st century},
  journal = {Agricultural Water Management},
  year = {2025},
  doi = {10.1016/j.agwat.2025.110044},
  url = {https://doi.org/10.1016/j.agwat.2025.110044}
}