Modeling water requirements of major crops and their responses to climate change in the North China Plain

The North China Plain (NCP) is one of the most important food production bases in China. However, its agriculture water resources are threatened by climate change. In this paper, the CROPWAT model is used to evaluate crop water requirement (CWR), crop green water requirement (CGWR), and crop blue water requirement (CBWR) for main crops in NCP (winter wheat, summer maize, cotton, millet, and soybean) with a spatial resolution of 5 arc-minute from 1961 to 2010. Their responses to future climate changes are investigated. The results show that the mean annual total CWR of the main crops during growing periods amounted to 114.68 km(3) a(-1) in the past 50 years. More than 72 % of CWR to support NCP crop production is green water. The spatial distributions of CWR, CGWR, and CBWR are closely related to the planting areas and irrigation availability. Summer maize, millet, and soybean are high CGWR crops with proportions of above 84 %, while the lowest CGWR proportion is in winter wheat, 58.89 %. For climate change impacts in future, holding the crop planting system and irrigation conditions unchanged, it is projected that the total CWR in 2030s will require approximately 8.75-11.25 km(3) a(-1) additional water. Results show that the CWR increase in 2030s is mainly due to the increase in temperature. Under the projected temperature in 2030s and the current rainfall scenario, total CWR, CGWR, and CBWR increments were 8.58, 1.76, and 6.82 km(3) a(-1), respectively. Nearly 80 % of the CWR increment is from the increase in CBWR. Therefore, agricultural water shortage crisis will further aggravate under future climate change scenarios in NCP, and effective water-saving measures must be taken to mitigate the negative effects of climate change