Darouich et al. (2026) Towards sustainable water use in intensive and super-intensive olive orchards of Alentejo across multiple scenarios for present and future climate

Identification

• Journal: Agricultural Water Management
• Year: 2026
• Date: 2026-01-24
• Authors: Hanaa Darouich, Tiago B. Ramos, L. S. Pereira
• DOI: 10.1016/j.agwat.2026.110176

Research Groups

• LEAF—Linking Landscape, Environment, Agriculture and Food Research Center, Associated Laboratory TERRA, Instituto Superior de Agronomia, Universidade de Lisboa, Portugal
• Centro de Ciência e Tecnologia do Ambiente e do Mar (MARETEC-LARSyS), Instituto Superior Técnico, Universidade de Lisboa, Portugal
• Instituto Nacional de Investigação Agrária e Veterinária, Portugal

Short Summary

This study developed guidelines for improving water use and optimizing irrigation scheduling in intensive and super-intensive olive orchards in Alentejo, southern Portugal, under present and future climate scenarios. It found that water-saving irrigation strategies can significantly reduce water consumption with manageable yield impacts, but climate change will increase irrigation requirements, necessitating adaptive management for sustainability.

Objective

• To develop guidelines for improving crop water use and optimizing irrigation scheduling for the most representative olive orchard systems in the Alentejo region.
• To characterize orchard systems based on tree density, fraction of ground cover (fc), and plant height (h).
• To estimate basal crop coefficient (Kcb) values for different tree density groups and crop stages using the Allen and Pereira (A&P) approach.
• To compute the soil water balance considering various scenarios including tree density, soil type, climate demand, and deficit irrigation strategies.
• To forecast effects and develop strategies to cope with climate change impacts on water use.

Study Configuration

• Spatial Scale: Roxo Irrigation District (RID), Montes Velhos, Aljustrel, southern Portugal (8561 hectares).
• Temporal Scale:
  • Historical period: 1979–2020.
  • Future climate projections: 2020–2060.

Methodology and Data

• Models used:
  • Allen and Pereira (2009) approach (A&P approach) for basal crop coefficient (Kcb) estimation.
  • SIMDualKc water balance model for daily soil water balance.
  • FAO56 dual crop coefficient method.
  • FAO-Penman Monteith (PM) equation for reference evapotranspiration (ETo).
  • FAO Penman-Monteith Temperature (PMT-ETo) equation for future ETo.
  • Curve number (CN) approach for runoff estimation.
  • Melo-Abreu et al. (2004) model for chilling accumulation (endodormancy).
  • Growing-degree-days (GDD) approach for crop growth stages.
  • Linear crop water-yield function (Doorenbos and Kassam, 1979) for yield impact assessment.
• Data sources:
  • Sentinel-2 Level 2A satellite images for estimating fraction of ground cover (fc).
  • Field measurements of crown diameter and plant height for fc calibration and h.
  • ERA5 weather reanalysis data (1979–2020) for historical climate.
  • Eight Global Circulation Models (GCMs) from CMIP6 (ACCESS-CM2, BCC-CSM2-MR, CMCC-ESM2, MIROC6, MIROC-ES2L, CNRM-CM6–1, CNRM-ESM2–1, MPI-ESM1-2-LR) for climate change projections (RCP4.5 and RCP8.5 scenarios).
  • Soil profile observations and calibrated parameters from previous studies for soil types.
  • SNIRH (2022) for groundwater table depth.

Main Results

• Basal crop coefficient (Kcb) values increased with higher tree density (greater fraction of ground cover, fc, and plant height, h) and stomatal adjustment factor (Fr).
• Deficit irrigation strategies led to a reduction in Kcb values by up to 15%, mainly due to stomatal adjustment under water stress.
• Seasonal crop water use (actual evapotranspiration, ETc act, and actual transpiration, Tc act) increased with higher climate demand. Tc values ranged from 388 mm for intensive hedge-prune orchards under low demand to 587 mm for super-intensive high-density hedgerow orchards under very high demand (full irrigation).
• Deficit irrigation significantly reduced both soil evaporation and crop transpiration. For the most severe deficit strategy (MAD = 1.25p), Tc act values ranged from 334 mm to 493 mm.
• Potential irrigation water savings increased with higher crop density, climatic demand, and the severity of deficit irrigation strategies. Fine-textured soils, with higher total available water (TAW), allowed for greater rainfall storage, reducing irrigation needs.
• Yield reductions were relatively small under moderate deficit irrigation (MAD = 1.05p and MAD = 1.15p) but became more pronounced at MAD = 1.25p.
• Climate change projections (RCP4.5 and RCP8.5) indicated increased crop water consumption due to rising temperatures, leading to higher irrigation requirements. Under full irrigation, seasonal irrigation depths for super-intensive high-density orchards are projected to increase by an average of 20% under RCP4.5 and 23% under RCP8.5.
• Significant uncertainty in future irrigation requirements was observed across climate models, primarily driven by rainfall variability.

Contributions

• Provides comprehensive guidelines for improving water use efficiency and optimizing irrigation scheduling in intensive and super-intensive olive orchards in the Alentejo region, addressing a critical need for sustainable management.
• Integrates the A&P approach for Kcb estimation with the SIMDualKc water balance model, leveraging both ground and remote sensing data, to offer a robust methodology for orchard-specific water management.
• Quantifies the potential for water savings through various deficit irrigation strategies and assesses their corresponding impacts on crop yields under current and future climate conditions.
• Offers a forward-looking assessment of climate change impacts on olive orchard water demand, providing a foundation for developing adaptive strategies to ensure the long-term sustainability of these production systems.
• Highlights the importance of considering specific orchard characteristics (density, canopy cover, height), soil properties, and climate variability in irrigation decision-making.

Funding

• FCT (Fundaç˜ao para a Ciˆencia e a Tecnologia, I.P.): Projects UIDB/50009/2025, UIDP/50009/2025, LA/P/0083/2020 (LARSyS), and UIDB/04129/2020 (LEAF).
• Project AGROSALT (Operation nº 15918; https://doi.org/10.54499/2023.17390.ICDT) of program COMPETE2030-FEDER-00704100, LISBOA2030-FEDER-00704100.
• FCT grants for H.D. (https://doi.org/10.54499/CEECIND/01153/2017/CP1430/CT0002) and T.B.R. (https://doi.org/10.54499/CEECIND/01152/2017/CP1461/CT0019).

Citation

@article{Darouich2026Towards,
  author = {Darouich, Hanaa and Ramos, Tiago B. and Pereira, L. S.},
  title = {Towards sustainable water use in intensive and super-intensive olive orchards of Alentejo across multiple scenarios for present and future climate},
  journal = {Agricultural Water Management},
  year = {2026},
  doi = {10.1016/j.agwat.2026.110176},
  url = {https://doi.org/10.1016/j.agwat.2026.110176}
}