The AquaCrop model is used to predict rice yield in response to different irrigation management in the Yanyun irrigation area in Yangzhou, China, and the constraints to rice production were identified to maximize water productivity based on model simulations. The model was calibrated by comparing measured and predicted canopy cover (CC), yield, and soil water content during the growing season in 2018. The results showed that, for CC simulations, R² was 0.99, RMSE was 3.6%, and NRMSE was 5.3%; for Biomass simulation, RMSE was 0.50 t/ha, and NRMSE was 5.3%. Different irrigation strategies were analyzed for a long-term simulation period from 1955 to 2014. The simulated rice yield increased rapidly as irrigation demand increased initially, and then gradually stabilized. The simulated rice yield fluctuated in the different years. The Pearson type-III model method was used to identify different hydrological years of wet, normal, and dry years. The analysis identified the wet year as 1991, normal year as 1981, and dry year as 1966. In the different rainfall years (1991, 1981, and 1966) water use efficiency (WUE), water productivity (WPet), and irrigation water productivity (IWP) were utilized to determine the irrigation strategy. The predicted highest WPet in the wet year was 1.77kg m⁻³, while the lowest WPet in the dry year was 1.13 kg m⁻³. The highest IWP was 19.78 kg m⁻³ in the wet year, and 9.32 kg m⁻³ in the normal year; while the lowest IWP in the dry year was 1.90 kg m⁻³. IWP was significantly higher in the rainy year, while WUE was significantly lower. On the other hand, WPet was more extensive in the wet year because the yield was higher, and the Evapotranspiration (ET) was smaller in comparison to the dry year.

High concentration of insecticides may appear in waters surrounding paddy fields shortly after application. Capturing the dynamic feature of this insecticide pulse may help control insecticide load to receiving waters. Based on continuous monitoring of the drainage process and two monitoring campaigns of three insecticides—chlorpyrifos, abamectin and thiamethoxam—in a paddy, this study examined the pattern of insecticide concentrations at different locations of paddy waters during the period of insecticide application accompanied with pest-control irrigation, and analyzed the factors affecting the environmental behavior of these insecticides. The results showed that the pulse-type drainage exhibited the following features: short duration (normally less than 1 d), large flow rate (as large as 4 L s⁻¹), frequent occurrence (20 times during a 40-d period) and long time interval (as long as 5 d). Concentrations of the insecticides with higher Henry’s constant and vapor pressure peaked quickly (within several hours) post application in the field ditch; more than half of chlorpyrifos and abamectin loads were detected within merely 1 h after application. The high insecticide concentrations in the ditch were partly attributed to the primary and secondary drift. Moreover, a new kinetic model was proposed to describe the behavior of chlorpyrifos at the field edge. It is recommended that controlled drainage be implemented for at least 1 d post application to prevent the loss of insecticides. Findings from this study may provide new insights into insecticide behavior in the paddy environment for preventing adverse environmental impacts.