Soil water balance modelling using SWAP An application for irrigation water management and climate change adaptation in citrus

The physically based agro-hydrological Soil, Water, Atmosphere and Plant (SWAP) model was applied in Andalucia (southern Spain) to simulate the water balance components in an irrigated citrus orchard. Direct measurements of soil water status using a frequency domain reflectometry (FDR) probe were used to calibrate the soil hydraulic functions using PEST, a parameter estimation package, and for crop coefficient (K-c) estimation. Model calibration and evaluation were carried out in 2008 using data from a citrus orchard considered representative of the typical agricultural practices in Andalucia. The SWAP model outputs agreed well with corresponding measured values in simulating soil water dynamics in-field. The model can be used in support of developing appropriate irrigation strategies for sustainable water management. An illustrative application using SWAP to assess the impacts of climate change on citrus production suggested increases in irrigation requirement of +6% to +16% for selected emissions scenarios for the 2050s and 2080s.