Simulating the Herbicide Molinate in Rice Paddies Using the RICEWQ Model

Contamination of drainage channels and creeks with pesticides used in rice production is of concern in south-eastern Australia. Of major concern is the herbicide molinate that is detected in over 25% of water samples. This pesticide has been the focus of researchers and environmental protection authorities due to continuing frequent detection off-farm despite improved application methods and water management guidelines. The objective of this study was to assess the rice pesticide model RICEWQ version 1.7.2 for its applicability in simulating pesticide in runoff in south-eastern Australia. The model was successfully calibrated against field data on water depths and molinate concentrations from a rice field in the Murrumbidgee Irrigation Area. It was found that the calibrated model was able to simulate the field data in the supply bay adequately; however it is not capable of modeling rice fields with multiple bays, which are much more complex than a single bay situation.