The Water Balance Model and Shallow Water Table Contribution in Irrigated Lowland Rice in the Tanjung Karang Irrigation Scheme in Malaysia

摘要

Quantifying the recharge of shallow ground water is important in understanding the effects of applied irrigation water in paddy fields. The shallow water table in lowland rice irrigation has long been neglected as an integral part of the water balance model. This study focused on the contribution of shallow ground water in lowland rice. Piezometric wells were set up at three different locations in the field to monitor the water table. The wells were mounted with ultrasonic sensors to monitor the water level fluctuations. Ground water level significantly responded to irrigation and the amount of rainfall. Shallow ground water level rose to the crop's root zone 65 d after rice transplant. Multivariate regression analysis was used to model the relationship between parameters in the water balance model. The coefficient of determination between the measured and the predicted standing water depth (SWD) was 0.94. However, 21% of the total irrigation water could have been saved when the contribution of the ground water was taken into account during irrigation. The rice plant could tap water supply from the ground water and compensate for evapotranspiration when there is no inundation.