Potential dynamic of irrigation water requirement for rice across Northeast China

Sufficient water is essential for maintaining rice production yields, but precipitation and ground water generally do not meet the requirements for rice growth. Irrigation is therefore necessary and the quantity of irrigation water requirement (IWR) is also highly dependent on climatic alterations. We utilized an ensemble of 20 fine-resolution downscaled global climate models to characterize the future dynamics of IWR across Northeast China, under two representative concentration pathway scenarios (RCP4.5 and RCP8.5). Crop evapotranspiration was a critical factor in IWR determinations and was estimated through the Hargreaves model. The model was recalibrated to optimize its performance and this resulted in normalized root mean squared errors of < 10%. Based on reliable crop evapotranspiration and effective precipitation data in baseline (1976–2005) and future periods (2036–2065 and 2070–2099), IWR decreased from southwestern Heilongjiang and western Jilin to the southeastern and northeastern areas. The IWR displayed a general increasing trend but overall the tendency decreased from west to east. The western areas were exposed to higher magnitudes of IWR increases, indicating that the water deficit for rice would be more severe in these regions. IWR levels increased with time slice under RCP8.5 relative to RCP4.5. The predicted IWR changes in future periods were greatest for Heilongjiang, followed by Jilin and Liaoning. In addition, Heilongjiang was predicted to have the most stable IWR in the future. These predictions of IWR dynamics highlight sensitive areas prone to water deficits and can serve as guides for specific irrigation schedules in the different rice growing regions across Northeast China.