Document Type : Research/Original/Regular Article
Authors
1
Civil Engineering Department, College of Engineering, Diyala University, Diyala, Iraq
2
Ministry of water Resources, State Commission for Dams & Reservoirs, Baghdad, Iraq
3
Civil Engineering Department, Tishk International University, Sulaimani, Iraq
Abstract
Water scarcity, shallow groundwater, waterlogging, and root-zone salinity interact strongly in arid agricultural systems. However, previous studies have commonly examined soil–water processes, drainage performance, optimization, or spatial variability separately. This separation limits the identification of management strategies that balance agronomic, hydrological, environmental, and economic objectives. To address this gap, this study developed and evaluated an integrated HYDRUS-2D–NSGA-II–GIS framework for irrigation–drainage management in Basra Governorate, southern Iraq. The methodological contribution lies in using process-based HYDRUS-2D outputs directly to evaluate candidate management strategies within NSGA-II and subsequently regionalizing the Pareto-optimal solutions through GIS to identify spatial management priorities. Decision variables represented irrigation-water application and scheduling, drainage operation and efficiency, groundwater control, and salinity-management practices. The objectives were to maximize crop yield and water-use efficiency while minimizing waterlogging duration, root-zone salinity, and operational costs, subject to constraints on irrigation water availability, canal and drainage capacity, crop water demand, groundwater depth, and crop salinity tolerance. Field surveys conducted during 2022–2024 measured soil-salinity values ranging from 3 to 6 dS m⁻¹. Under the baseline HYDRUS-2D simulation representing current management, volumetric soil-water content ranged from 0.18 to 0.27 m³ m⁻³, the average soil-water content was 0.22 m³ m⁻³, the waterlogging duration was 12 days month⁻¹, and the average root-zone salinity was 4.8 dS m⁻¹. For the management scenario selected by NSGA-II, the corresponding HYDRUS-2D outputs were 0.26 m³ m⁻³, 7.5 days month⁻¹, and 3.7 dS m⁻¹, respectively. Crop water-use efficiency increased by 31%, while wheat, rice, and date-palm yields increased by 17%, 18%, and 9%, respectively. The selected scenario illustrated trade-offs among water use, crop performance, waterlogging, salinity, and operational cost. These findings demonstrate that the integrated framework can quantify conflicting management trade-offs and translate Pareto-optimal solutions into spatially differentiated recommendations. Subject to local calibration and validation, the framework is potentially transferable to other arid and semi-arid agricultural regions affected by shallow groundwater, salinity, and constrained drainage.
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