Zolghadr‐Asli et al. (2025) Evaluating the potential of desalinated irrigation in water-stressed regions through optimized planting dates and irrigation strategies

Identification

• Journal: Agricultural Water Management
• Year: 2025
• Date: 2025-11-24
• Authors: Babak Zolghadr‐Asli, Neil McIntyre, Slobodan Djordjević, Raziyeh Farmani, Liliana Pagliero, Gabriel Perez
• DOI: 10.1016/j.agwat.2025.110009

Research Groups

• Sustainable Minerals Institute, The University of Queensland, Brisbane, Australia
• Centre for Water Systems, University of Exeter, Exeter, UK
• The School of Civil Engineering, The University of Queensland, Brisbane, Australia
• Australian Rivers Institute, Griffith University, Brisbane, Australia
• WSP Australia, Australia

Short Summary

This study evaluates the potential of desalinated irrigation in water-stressed regions by optimizing planting dates and irrigation strategies for tomato production in Chile's Atacama region. It demonstrates that adjusting planting dates combined with optimal deficit irrigation significantly improves water productivity and profit margins, potentially offsetting the costs of desalinated water, especially when leveraging economies of scale.

Objective

• To what extent can optimizing the irrigation schedule to accommodate the biological needs of a given crop during growth stages and rescheduling cultivation initiation improve water productivity?
• What are the impacts of inherent uncertainties of such assessment, most notably soil properties, on crop yield production and, in turn, water use productivity?

Study Configuration

• Spatial Scale: Copiapó Valley, Atacama region, Chile (case study for tomato production).
• Temporal Scale: Simulation period from 1998 to 2019 (22-year window).

Methodology and Data

• Models used:
  • Crop growth model: AquaCrop-OSPy (Python-based interpretation of FAO AquaCrop).
  • Optimization algorithm: Self-tuning multi-layer (STML) algorithm.
  • Uncertainty analysis: Monte Carlo simulation.
• Data sources:
  • Soil type: Harmonized World Soil Database (HWSD) (Sandy Loam).
  • Meteorological and hydrological inputs: Río Copiapó en Ciudad de Copiapó station within the CAMELS-CL dataset.
  • Crop parameters: Cultivar harvest index (HI0) = 0.38 for tomato.
  • Economic data: Local data from the 2021/22 season for outdoor tomato production (ODEPA Oficina de Estudios y Políticas Agrarias, 2022).

Main Results

• Rescheduling the planting date from mid-November to mid-December (specifically 15 December) significantly improved water productivity (WP).
• Scenario V (optimal deficit irrigation with optimal planting date) resulted in a 61% increase in average annual fresh yield compared to the baseline (Scenario I) and a 36% improvement relative to optimal deficit irrigation alone (Scenario IV).
• Average annual irrigation requirements showed a slight downward trend with later planting dates, attributed to lower average temperatures during the shifted crop growth window.
• Even without irrigation, a rescheduled planting date (Scenario VI; average WP: 1.01 kg/m³) outperformed the baseline conditions (Scenario I; average WP: 0.86 kg/m³).
• Economic analysis indicated that Scenario VII (full irrigation, optimal planting date) and Scenario V (optimal deficit irrigation, optimal planting date) yielded the highest average net marginal profits ($ CLP 7.3 million and $ CLP 6.9 million, respectively, compared to $ CLP 1.2 million for the baseline).
• While the additional costs of desalinated water ($ USD 2700 to $ USD 26,000 per hectare) could reduce profit margins, higher-yielding, robust strategies (e.g., Scenario V) remained economically feasible, particularly when considering economies of scale in both agriculture and desalination.
• Monte Carlo sensitivity analysis, using 100 synthetic soil profiles, showed an average fresh yield of 42.3 ± 3.4 tonnes per hectare, an average annual irrigation of 262 ± 10 mm per hectare, and an average water productivity of 0.803 ± 0.032 kg/m³, highlighting the impact of soil variability.

Contributions

• Demonstrates the potential of desalinated water to enable flexible irrigation strategies and optimized planting dates, decoupling agricultural production from hydrological cycle constraints in water-stressed regions.
• Provides a proof-of-concept framework integrating a crop simulation model (AquaCrop-OSPy) with a self-tuning optimization algorithm (STML) to maximize water productivity and economic returns.
• Quantifies the economic feasibility of using desalinated water for irrigation in a specific case study (tomato production in Atacama, Chile), considering operational costs, market fluctuations, and economies of scale.
• Analyzes the robustness of irrigation strategies against uncertainties in soil properties using Monte Carlo simulation, offering insights into practical implementation challenges.
• Highlights the value of supply-side flexibility in water access as a complementary approach to demand-side management for enhancing agricultural resilience and food security.

Funding

• QUEX Institute (joint initiative of University of Exeter and The University of Queensland).

Citation

@article{ZolghadrAsli2025Evaluating,
  author = {Zolghadr‐Asli, Babak and McIntyre, Neil and Djordjević, Slobodan and Farmani, Raziyeh and Pagliero, Liliana and Perez, Gabriel},
  title = {Evaluating the potential of desalinated irrigation in water-stressed regions through optimized planting dates and irrigation strategies},
  journal = {Agricultural Water Management},
  year = {2025},
  doi = {10.1016/j.agwat.2025.110009},
  url = {https://doi.org/10.1016/j.agwat.2025.110009}
}