Development of a waterlogging analysis system for paddy fields in irrigation districts

Waterlogging is one of the most important agricultural disasters affecting rice. In this study, we developed a waterlogging analysis system for paddy fields in irrigation districts with 7 modules, including pretreatment, hydrological computations and waterlogging computations. The newly developed system can consider the effects of both landform features and human interventions in irrigation districts. Observational data from the Gaoyou Irrigation District during 2014 and 2015 were applied to calibrate and validate a waterlogging analysis system, respectively. The results indicated that the waterlogging analysis system could accurately predict the water levels in both the calibration (R-2 > 0.97) and validation (R-2 > 0.92) periods. Sensitivity and uncertainty analyses of the yield reduction rate indicated that saturated soil moisture and shape parameters (a and n) were the dominant soil hydrodynamic parameters affecting the simulated yield reduction rates. The weighted mean yield reduction rate of field areas decreased with increasing shape parameters and increased with increasing soil moisture saturation. However, further analysis showed that the maximum yield reduction rate exhibited a trend similar to that of saturated soil moisture, which indicated that the backwater effects of the river and ditch water level changes had a greater influence than the soil hydrodynamic parameters on the yield reduction rate, especially in low-elevation fields. In addition, the relationship between the yield reduction rate and field elevation could be fitted by an exponential function (R-2 = 0.83), and the field pond depth decreased linearly with a reduction in field elevation in both 2014 (R-2 = 0.36, p < 0.01) and 2015 (R-2 = 0.64, p < 0.01). The proposed waterlogging analysis system could be a useful tool for evaluating the effects of waterlogging on rice production in the studied irrigation district or in other regions with similar climatic conditions.