Responses of rice yield, irrigation water requirement and water use efficiency to climate change in China: Historical simulation and future projections

Rice is one of most important crops in China, accounting for approximately 18% of total cultivated area. Rice productivity is significantly affected by undergoing climate change and vulnerable with water stress. Therefore, investigating the responses of rice growth and water resources utilization to more pronounced climate change is of great importance for water resources planning and management in terms of maintaining the ecosystem integrity and ensuring the food security. In this study, the changes of rice yield, water consumption (ET), irrigation water requirement (IWR), water use efficiency (WUE) and irrigation water use efficiency (IWUE) from 1961 to 2010 in three typical sites (Kunshan and Nanjing in the Yangtze River Basin, and Kaifeng in the Yellow River Basin) in rice plantation region of China were evaluated by means of validated rice crop model ORYZA2000. Their responses to future climate scenarios of 21 century were investigated by driving ORYZA2000 with downscaling climatic data from HadCM3 (Hadley Centre Coupled Model version 3) under A2 and B2 emission scenarios with the help of a statistical downscaling method (SDSM). The results exhibit a significant decline in rice yield was identified by 49.3 kg ha−1, 32.0 kg ha−1 and 45.8 kg ha−1 for Kunshan station, Nanjing station and Kaifeng station, respectively, in the past 50 years due to obviously shortened rice growth duration (0.20 day a−1, 0.15 day a−1 and 0.27 day a−1, respectively). While changes of ET and IWE were different for three stations representing by significant increase of ET and IWE in Kunshan, non-significant increase in Nanjing and significant decrease in Kaifeng. Whereas accompanying production reduction, simulated WUE and IWUE for three stations all presented significant deceasing trends ranging from 0.06 kg ha−1 mm−1 to 0.16 kg ha−1 mm−1. The future projection results under IPCC SRES A2 and B2 emission scenarios indicated the generally negative effect of climate warming to rice yield (maximum by −18.9% decline in 2090s in Kunshan) during the 21 century due to remarkable shortened growth period, resulting in generally depressed WUE and IWUE, although there would be the distinct response of the ET and IWR to future climate change for the three stations. Meanwhile, the increase of CO2 concentration under future climate is beneficial to raise the rice yield, alleviate crop water consumption and irrigation water requirements and improve the water use efficiencies of rice in a certain degree. Further works should be carried out to capture simulation uncertainties in climate change impact assessment with consideration of interactions among anthropogenic activities, environmental and biological factors.