Elsevier

Science of The Total Environment

Volume 656, 15 March 2019, Pages 373-387
Science of The Total Environment

Effects of temperature, precipitation and carbon dioxide concentrations on the requirements for crop irrigation water in China under future climate scenarios

https://doi.org/10.1016/j.scitotenv.2018.11.362Get rights and content

Highlights

  • We predict the changes in irrigation water requirement for four crops in China.

  • The irrigation water requirements for crops are dominated by various climatic factors.

  • The irrigation water requirements under RCP8.5 reduce mainly by the CO2 effect.

  • Northwestern China always requires vast amounts of irrigation water for crops.

Abstract

Maize, rice, wheat and soybean—the major staple food crops in China—have a crucial role in national food security and economic development. Predictions of changes in the requirements for irrigation water in food crop production under climate change may provide scientific support for the optimum allocation of water resources and measures to mitigate climate change. We conducted a spatial grid-based analysis using projections of future climate generated by a bias-correction and spatial disaggregation multi-model ensemble for three representative concentration pathway scenarios (RCP2.6, RCP4.5 and RCP8.5) adopted by the fifth phase of the Coupled Model Intercomparison Project. We investigated the effects of climate change associated with increasing temperature, changed precipitation and increased concentrations of atmospheric carbon dioxide (CO2) on the irrigation water requirements of maize, rice, wheat and soybean in China at the end of the 21st century (2081–2100). Our results indicate that the irrigation water requirements of maize and wheat are driven by temperature and especially by CO2 concentrations in the northwest interior area as a result of the low rainfall and high rates of evaporation; the irrigation water requirement of soybean is influenced by a combined effect of temperature, precipitation and CO2 concentration, whereas the irrigation water requirement for rice is dominated by precipitation alone in the southern coastal region, which has high rainfall. The irrigation water requirements of crops decrease mainly as a result of the beneficial effects of CO2 on plant growth in China. The regions requiring vast amounts of irrigation water as a result of climate change are mainly concentrated in northwestern China. The effects of climate change affect the requirement for irrigation water, especially under high-emission scenarios, and should be studied further to design appropriate adaptation strategies for the management of agricultural water to maintain the sustainable development of agriculture.

Graphical abstract

Irrigation water requirements with temperature-only (T-only), precipitation-only (P-only) and carbon dioxide-only (CO2-only) for (a) maize, (b) rice, (c) soybean and (d) wheat under the representative concentration pathway scenario RCP8.5 in China in the 2010s (2006–2020), 2030s (2021–2040), 2050s (2041–2060), 2070s (2061–2080), and 2090s (2081–2100).

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Introduction

Irrigation has a major role in food security and the alleviation of poverty in China. Over 70% of the water consumed in China is used for agricultural irrigation, with irrigation water applied to >75% of crops on >30% of agricultural land (Thomas, 2008; Xiong et al., 2009). As irrigation is the major use of water in agricultural regions, the capacity to supply irrigation water is crucial in the long-term development of water resources and in decision-making about future agricultural production in China.

The irrigation water requirement (IWR) is the amount of water that must be supplied to a crop via irrigation to achieve optimum crop growth, taking into consideration the losses incurred during the transport and application of the irrigation water. Global factors such as climate change [i.e., increasing temperatures, fluctuations in precipitation and increasing concentrations of atmospheric carbon dioxide (CO2)] are placing increasing stress on agricultural systems and drive variations in the IWR (Wang et al., 2014).

A number of studies over the past few decades have quantified the impact of future climate change on irrigation at regional and global scales. Significant increases have been estimated for the long-term IWR as a result of a warming climate and increased evaporative demand (e.g., Fischer et al., 2007; Pfister et al., 2011; Konzmann et al., 2013; Elliott et al., 2014). Increased atmospheric concentrations of CO2 have been shown to directly affect transpiration via both the physiological and structural responses of plants, which tend to reduce their leaf stomatal conductance and thus the rate of evapotranspiration, improving the efficiency of water use by crops (Gerten et al., 2007; Hatfield et al., 2011). Therefore quantifying and analyzing the spatial and temporal characteristics of the regional demand for irrigation water by agriculture is important in developing strategies for water management under the future impacts of climate change and the associated demographic, socioeconomic and technological changes.

Assessments of the geographical distribution of crop water requirements in China are widely available (e.g., Leng and Tang, 2014). However, data on the extent to which variations in temperature, precipitation and atmospheric CO2 concentrations will affect future IWRs for specific crops start later and are fairly sparse. Some studies do not take into account the use of water by specific crops. For example, Thomas (2008) modeled the effects of climate change on irrigation requirements in China with high-resolution gridded climate datasets; but he identified the crops as main, second and third crops according to the cropping system. Some studies take into account the specific field crops without consideration of the effect of CO2 on the use of water by crops. For example, Liu et al. (2009) provided IWRs for 30 different crops estimated using the Food and Agriculture Organization (FAO) Penman–Monteith equation and the crop coefficient method based on meteorological data for the period 1970–2000 from observation stations and statistical data about the stages of crop growth in different areas of China. Cong et al. (2011) reported increases in the IWRs of crops in China due to increases in future temperatures using the FAO Penman–Monteith equation, crop coefficients and the Köppen climate classification system under future emission scenarios.

To improve these methods and to fill some gaps in research, this study applied a standard method of estimating future IWRs (including the crop coefficient approach and the FAO Penman–Monteith equation incorporating the effect of CO2) based on gridded climatic data from 2006 to 2100 simulated by six bias correction and spatial disaggregation climate projections in the fifth phase of the Coupled Model Intercomparison Project (CMIP5) archive under three representative concentration pathway (RCP) scenarios (RCP2.6, RCP4.5 and RCP8.5). The aims of this study were to: (1) explore the long-term temporal and spatial variations in the IWR of major crops (maize, rice, wheat and soybean) in China in the future; (2) conduct an analysis of how the IWR responds to climate change associated with variations in temperature, precipitation and CO2 concentrations; and (3) investigate the dominant climatic factors governing the behavior of the crop-specific IWRs. The results were compared with historical publications to determine the validity and precision of this method. These results may provide reference values for climate adaptation strategies and the sustainable development of agriculture under scenarios of climate warming and water shortages. The method developed in this study may also provide guidance for the scientific research in agro-climatology and the establishment of reasonable agricultural irrigation schemes.

Section snippets

Crop types

Cereal and legume crops—such as maize (Zea mays L.), rice (Oryza sativa L.), wheat (Triticum aestivum L.) and soybean (Glycine max L.)—are cultivated and produced in most cropland areas in China (http://data.stats.gov.cn) (Leff et al., 2004). The majority of the cropland areas are in southern and eastern China in the humid, rainy, monsoon climate zone, although a few are located in the dry area of northwest China. Potential changes in the IWRs for these four crops are important in assessing the

Relative changes in the IWR for different crops

For maize, the IWR decreased over a wide area of the IRB by the 2090s relative to the 2010s under the RCP2.6, RCP4.5 and RCP8.5 scenarios. The relative changes on the national scale were −42.40, −3.78 and −80.14%, respectively (Fig. 2, Fig. 3). The decrease was larger under the RCP8.5 scenario, but a sharp increase also occurred in some western parts of the IRB under the RCP4.5 scenario.

For rice, the IWR showed large increases in the PRB by the 2090s relative to the 2010s under the RCP2.6,

Comparison with similar studies

As per Table 4, this study showed identical or similar results of spatial variations in the IWRs of crops compared with the results reported by Döll (2002), Cong et al. (2011) and Konzmann et al. (2013). This study effectively simulated the decreased IWRs of maize and wheat in IRB and the fluctuant IWR of rice in PRB. And our simulations were closest to the results reported by Konzmann et al. (2013), who quantified global changes in the irrigation requirements of major crop types using the

Conclusions and perspective

This study investigated the effects of future climate change on the IWRs of maize, rice, soybean and wheat in China using the FAO Penman–Monteith equation (incorporating the CO2 effect) and the crop coefficient approach. Substantially different spatiotemporal patterns of the IWR were derived under different RCP scenarios due to the combination of increasing temperatures, regional increases in precipitation and the beneficial effects of CO2 on plants. The regions that will require irrigation

Acknowledgments

The authors are indebted to Jing Ge and Gaopeng Li at the Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, and Yao Li at the College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, for their suggestions. The authors are also grateful to the anonymous referees and the handling editor for the provision of constructive and useful reviews and advice that have led to a substantially improved revised paper. This study was funded

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