Martínez-López et al. (2026) Parameterization of a simplified soil water balance model using actual evapotranspiration measurements to optimize vineyard irrigation scheduling

Identification

• Journal: Agricultural Water Management
• Year: 2026
• Date: 2026-11-06
• Authors: José Antonio Martínez-López, Alfonso Domínguez, A. Martínez-Romero, Diego Sebastiano Intrigliolo, F. Montoya, R. López-Urrea
• DOI: 10.1016/j.agwat.2026.110897

Research Groups

• University of Castilla – La Mancha, University Institute for Research in Biotechnology, Agronomy and Sustainability (IBAS), Regional Centre of Water Research (CREA) and “Remote Sensing, Agronomy and Irrigation”, associated Unit to CSIC by CIDE, Albacete, Spain
• Desertification Research Centre (CIDE), CSIC-UV-GVA, Moncada, Valencia, Spain

Short Summary

This study calibrated and validated the RETOAGUA (RA) decision-support system for simulating vineyard evapotranspiration and crop cycle length under semi-arid conditions in Spain. The RA model demonstrated strong agreement with lysimeter observations under well-watered conditions and acceptable performance under deficit irrigation, highlighting its potential as a user-friendly tool for optimizing vineyard irrigation scheduling with minimal input requirements.

Objective

• To determine the duration of the main growth stages of vines (Vitis vinifera L., cv. Tempranillo) in terms of cumulative growing-degree-days (CGDDs).
• To calibrate and validate the parameters required by the RA model for simulating actual crop evapotranspiration (ET c act ) of fully irrigated vineyards.
• To calibrate and validate the RA model for simulating the ET c act of vineyards under water deficit conditions.

Study Configuration

• Spatial Scale: Two experimental areas in southeast Spain: Albacete (Castilla–La Mancha) and Requena (Valencia province), both semi-arid Mediterranean environments. Phenological monitoring data from the Castilla–La Mancha Irrigation Advisory Service covered a broader region.
• Temporal Scale:
  • Phenological monitoring: 8 years (2002–2010).
  • Well-watered ET c act assessment: 3 years (2007–2009).
  • Deficit irrigation ET c act assessment: 4 years (2001–2004).

Methodology and Data

• Models used:
  • RETOAGUA (RA) model, a decision-support system based on the MOPECO model.
  • Daily soil water balance approach.
  • Single crop coefficient (K c ) approach (ET c = ET o × K c ).
  • FAO Penman-Monteith ET o equation for reference evapotranspiration.
  • Cumulative Growing Degree Days (CGDD) methodology with the double triangle method for phenological stages.
• Data sources:
  • Phenological data: 39 phenological crop monitoring records of Tempranillo vineyards from the Castilla–La Mancha Irrigation Advisory Service (2002–2010).
  • Actual evapotranspiration (ET c act ) under well-watered conditions: Monolithic large weighing lysimeter measurements (3 m x 3 m x 1.7 m) in Albacete (2007–2009).
  • Actual evapotranspiration (ET c act ) under deficit irrigation conditions: Soil water content (SWC) measurements using capacitance probes (up to 1.2 m depth) in commercial Tempranillo vineyards in Requena (2001–2004).
  • Climatic data: Automated weather stations located near experimental sites, recording air temperature, relative humidity, wind speed, radiation, and precipitation.

Main Results

• Phenology Calibration: Optimal threshold temperatures for CGDD were 38 °C (upper) and 6 °C (base), consistent with reported values for grapevine. The overall variation in crop cycle length was below 10%.
• ET c act Calibration (Well-watered, 2007): The RA model showed strong agreement with lysimeter observations, with Root Mean Square Error (RMSE) below 0.5 mm day⁻¹ (except for vegetative growth at 0.71 mm day⁻¹), Normalized Root Mean Square Error (NRMSE) between 10.1% and 20.1%, Model Efficiency (EF) of 0.91, and coefficient of determination (R²) of 0.91 for the entire crop cycle.
• ET c act Calibration (Deficit Irrigation, 2003–2004): Performance ranged from acceptable to excellent, with RMSE between 0.20–0.55 mm day⁻¹, NRMSE between 10.0–25.0%, EF between 0.27–0.92, and R² between 0.59–0.99.
• ET c act Validation (Well-watered, 2008–2009): Consistent high performance with RMSE between 0.45–0.62 mm day⁻¹ (except vegetative growth at 0.79 mm day⁻¹), NRMSE between 17.8–18.5%, EF of 0.81, and R² between 0.82–0.88 for the entire crop cycle.
• ET c act Validation (Deficit Irrigation, 2001–2002): Exhibited higher variability and lower accuracy, with RMSE between 0.44–1.57 mm day⁻¹, NRMSE between 26.6%–72.1%, and R² between 0.54–0.88. Negative EF values were observed in some cases, attributed to observational uncertainty from point-based soil water sensors and simplifying model assumptions.
• Model Usability: The RA model requires only 10–14 easily obtainable parameters, significantly reducing the complexity and data requirements compared to other existing models (e.g., SIMDualKc, VINTEL).

Contributions

• Provides a calibrated and validated parameterization of the user-friendly RETOAGUA (RA) model for vineyard evapotranspiration and phenology under semi-arid Mediterranean conditions.
• Addresses the gap in agricultural modeling by offering a scientifically robust yet practically usable decision-support system for farmers and technicians, requiring significantly fewer inputs than complex research-oriented models.
• Demonstrates the potential for reliable irrigation scheduling with limited data, enhancing water use efficiency in water-scarce regions.
• Highlights the challenges and uncertainties associated with point-based soil water measurements for ET c act estimation under localized drip irrigation and deficit conditions.

Funding

• Spanish Ministry of Science, Innovation, and Universities (FPU21/02676 contract for J.A. Martínez-L´ opez)
• Agencia Estatal de Investigaci´ on with FEDER co-financing (Project PID2021–123305OB-C31 for R. L´ opez-Urrea)
• Regional Government of Castilla-La Mancha (JCCM, Spain)
• University of Castilla – La Mancha

Citation

@article{MartínezLópez2026Parameterization,
  author = {Martínez-López, José Antonio and Domínguez, Alfonso and Martínez-Romero, A. and Intrigliolo, Diego Sebastiano and Montoya, F. and López-Urrea, R.},
  title = {Parameterization of a simplified soil water balance model using actual evapotranspiration measurements to optimize vineyard irrigation scheduling},
  journal = {Agricultural Water Management},
  year = {2026},
  doi = {10.1016/j.agwat.2026.110897},
  url = {https://doi.org/10.1016/j.agwat.2026.110897}
}