气候变化条件下海河平原作物灌溉策略优化模拟

    Optimization of crop irrigation strategies using modeling in Haihe Plain under climate change

    • 摘要: 定量化评估未来气候变化条件下农田水分利用和作物产量变化,并探究适应气候变化的灌溉策略对水资源紧缺粮食主产区的农业可持续发展具有重要意义。该研究应用改进的SWAT(soil and water assessment tool)模型与CMIP6(coupled model intercomparison project phase 6)的大气环流模式(general circulation model, GCM)相结合的方法,在3种共享社会经济路径(SSP1-2.6, SSP2-4.5和SSP5-8.5)下评估了未来时期(2041-2070年)海河平原实际蒸散量、灌溉量、地下水净使用量(net groundwater use, NGU)和作物产量的变化情况,探究了未来气候情景中适宜的作物灌溉策略。结果表明:1)与历史时期(1971-2000年)相比,未来时期区域年实际蒸散量增加5.5%、年灌溉量和年地下水净使用量分别减少5.9%和25.8%。在SSP5-8.5情景下,年实际蒸散量的增幅最低,年灌溉量和年地下水净使用量的减幅最高。2)相较于历史时期,未来时期冬小麦和夏玉米产量分别增加14.3%和6.5%,其中夏玉米产量增幅随温室气体排放情景的增强而降低。3)在未来气候情景中,雨养夏玉米结合冬小麦拔节期进行灌溉(灌水定额为25 mm,根据自动灌溉系统确定灌水频率)或可最大限度地实现该区地下水资源恢复。从确保粮食安全的视角,推荐雨养夏玉米与冬小麦在拔节期和灌浆期灌溉相结合。研究结果可为区域农业水资源合理规划、可持续的粮食生产政策的制定提供参考。

       

      Abstract: The Haihe Plain has made a great contribution to national food security in the world. The stable production of grain crops can rely mainly on groundwater extraction for irrigation, thus leading to the overexploitation of groundwater in the region. Additionally, the ever-increasing global climate can also threaten water resources and food production. Deficit irrigation can be expected to serve as a water-saving technique under current climate conditions, in order to significantly improve water use efficiency. However, much more irrigation water can be required to fully meet the normal growth needs of crops, particularly with the general increase in temperatures. It is a high demand to quantitatively assess the changes in crop water use and crop yields under future climate scenarios. Adaption irrigation can be used to explore climate change for the sustainable development of agriculture in the major food-producing regions with scarce water resources. In this study, an enhanced SWAT model was combined with the multiple general circulation models (GCMs) from CMIP6, in order to simulate the climate and irrigation scenarios. The improved SWAT model included some enhancements in two aspects: one was an automatic irrigation using MAD (management allowed depletion), and another was the dynamic CO2 input. Additionally, three shared socioeconomic pathways (SSPs) were selected, namely SSP1-2.6, SSP2-4.5, and SSP5-8.5. Firstly, the enhanced SWAT model and multiple GCMs were applied to simulate the actual evapotranspiration (ETa), irrigation, net groundwater use (NGU), and crop yields under the SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios in the future period (2041-2070). Furthermore, the appropriate irrigation strategies were explored for the future scenarios of climate change. The results showed that: 1) Annual ETa increased by 5.5%, whereas, the annual irrigation and NGU decreased by 5.9% and 25.8%, respectively, in the future period, compared with the historical period (1971-2000); Under the SSP5-8.5 emission, the annual ETa increased the least, whereas, the annual irrigation and NGU decreased the most. 2) The winter wheat and summer maize yield increased by 14.3% and 6.5%, respectively; There was the declined yield of summer maize under the greenhouse gas emission scenario. 3) In the future climate, the appropriate schedule of irrigation was achieved in the jointing stage of winter wheat with the rainfed summer maize, indicating the maximum groundwater recovery. In food security, it is recommended irrigation during the jointing and filling stages of winter wheat with the rainfed summer maize. 4) In terms of grain production and groundwater resource recovery, the irrigation strategies can be recommended to vary among different zones. In Baoding, Shijiazhuang, Xingtai, and Hengshui zones, irrigation can be applied during both the jointing and filling stages. In the Handan zone, irrigation can be recommended only during the jointing stage, while in the Langfang zone, it should be during the filling stage. Finally, irrigation can be advised before winter and during the filling stage of winter wheat in the Cangzhou zone. The findings can provide for the rational planning of regional agricultural water resources and sustainable food production.

       

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