Simulation of hydrology following various volumes of irrigation to soil with different depths to the water table

Abstract

AbstractVertical water fluxes at the water table and in the subsoil need to be quantified because of their significance for the supply of water to crops and the control of soil salinization in areas with shallow groundwater. A soil–water–atmosphere–plant (SWAP) model was calibrated using measured values of soil water content and the water fluxes at the water table. The measurements were taken in a field experiment where the depth to groundwater and the volume of irrigation water applied were controlled. The calibrated SWAP model was then used to simulate the soil water content and fluxes at the water table and in the subsoil under different irrigation and groundwater conditions. The predicted values provided a quantitative insight into specific terms in the water balance equation together with soil water fluxes in the subsoil that cannot be measured directly by field instruments. Crops utilized significant amounts of water from deeper soil layers and directly from groundwater, when the volume of irrigation decreased and the depth to the water table was <3.0 m. Depth to the water table significantly influenced water fluxes occurring in the soil profile over the period when evaporation dominated the hydrological cycle. Shallow groundwater is a very significant water resource for meeting the water requirement of crops. In practice, the frequency and quantity of irrigation need to be varied according to groundwater conditions.