2018-9-21

Varying benefits of irrigation expansion for crop production under a changing climate and competitive water use among crops

Masashi Okada, Toshichika Iizumi, Takaaki Sakamoto, Mizuki Kotoku, Gen Sakurai, Yasuaki Hijioka, and Motoki Nishimori

Information of Paper

Varying benefits of irrigation expansion for crop production under a changing climate and competitive water use among crops

Authors:Masashi Okada, Toshichika Iizumi, Takaaki Sakamoto, Mizuki Kotoku, Gen Sakurai, Yasuaki Hijioka, and Motoki Nishimori

Year:2018
Journal:Earth’s Future, 6

Link to the paper

Keywords

Adaptation, Agricultural system, Climate change, Irrigation, Crop model, Hydrologic model

Abstract

Replacing rainfed cropping systems with irrigated systems has been deemed an effective agricultural adaptation measure in response to climate change. However, few agricultural impact assessments have considered changes in the water availability because of climate change and water use competition among crops. Here we assessed future global crop production under a changing climate and expanded surface water irrigation using the large-scale crop-river coupled model CROVER. The future irrigated area was estimated by extrapolating from the historical linear trends. We present three interesting cases from this global analysis. The results under a high-emission scenario (Representative Concentration Pathway 8.5) showed that, in response to irrigation expansion, maize production in Europe will increase, whereas rice production in East Asia will not increase because of competitive water use between rice and other crops (Fig. 1). Furthermore, we found that future precipitation over crop-producing areas in the Indus River watershed will decrease but that increased precipitation in the higher mountainous areas of the watershed will compensate for these diminished water resources, thereby reducing drought damage. Our findings reveal that competitive water use among crops and the geographical patterns of future changes in precipitation influence the benefits of expanding irrigation for crop production under a changing climate.

Figure1ab varying benefits of irrigation expansion
Fig1. Difference of (a) rice yield and (b) maize yield under changes in both climate and irrigated area to one under change in climate without any changes in irrigated area in each future period. The bar graph and the associated error bar show the mean and uncertainty (minimum-maximum range) of projections under five climate change scenarios. USSR = former Union of Soviet Socialist Republics; MEA = Middle East and Africa.

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