Distributed Application of SWAP Model for Intra-Daily Simulation of an Agricultural System with Subsurface Drainage

Despite the high capability of field-scale agro-hydrological models to simulate plant growth interactions with water and solute transport in agricultural systems, their application to real conditions of large sugarcane fields in Khuzestan province faces many challenges, including spatial heterogeneity of irrigation scheduling across the field, the difficulty of determining initial and boundary conditions as well as several unknown model parameters, and data–intensiveness of calibration procedure. This work aimed to implement the agro-hydrological modeling under real operational conditions of large fields with surface/subsurface drainage. In this work, a distributed agro-hydrological modeling scheme was developed through the application of a modified version of the SWAP model and an improved variant of the Unified Particle Swarm Optimization (UPSO) algorithm with capability of sub-daily calibration and simulation of controlled drainage. The developed model was applied to a sugarcane field with subsurface drainage with planted sugarcane (CP48-103 cultivar) in Imam Khomeini Sugarcane Agro-industrial company farms, during 2010-07-19 to 2011-12-11 (481 days). The results revealed the reasonable performance of the developed modeling scheme in retrieving the measured soil moisture, groundwater level, subsurface drainage outflow (with an EF of 0.901, 0.827, and 0.877 for calibration dataset; and 0.514, 0.798, and 0.672 for validation dataset, respectively), soil water solute concentration, subsurface drainage outflow salinity (with a NRMSE of 0.039 and 0.096 for calibration dataset; and 0.154 and 0.046 for validation dataset, respectively), Leaf Area Index, cane yield, and sucrose yield (with an EF of 0.995, 0.999, and 0.972, respectively).