地下水压采下河北平原冬小麦面积及耗水变化

Changes in the area and water consumption of winter wheat under limiting groundwater exploitation in the Hebei Plain

  • 摘要: 河北省是我国的重要粮食生产基地, 资源性缺水与长期高强度的农业生产, 导致河北平原水资源危机进一步加剧。面对水资源安全与粮食安全的矛盾, 河北省政府自2014年起实施地下水压采政策, 在农业生产上开展季节性休耕、实施旱作雨养、推广节水农业等措施。为探明地下水压采政策下河北平原冬小麦种植面积与耗水特征的变化, 本研究利用MODIS NDVI数据提取了河北平原2009—2019年冬小麦种植空间分布, 结合TSEB(基于双源能量平衡模型)蒸散产品以及农业生产统计数据, 对压采政策实施前后进行了比较研究, 并调研了相关变化的驱动因素。结果表明: 河北平原的冬小麦种植面积在2009—2019年持续增长了18.37万hm2, 压采政策实施后表现为东部增加西部减少的特征, 总体上增加10.4万hm2。通过实地调研发现, 农业生产经营者追求种植效益以及城市化导致冬小麦面积减少, 政府保障粮食安全的鼓励种粮政策以及冬小麦种植全程机械化程度的提高则促使其种植面积增加。与地下水压采政策实施前相比, 压采后冬小麦的蒸散量与总耗水量分别增加32.58 mm和10.9亿m3。季节性休耕期间, 休耕地不抽取地下水灌溉, 相比于麦田, 休耕地能够减少73 mm的蒸散耗水。2009—2019年冬小麦平均水分利用效率为1.67 kg∙m−3。地下水压采政策实施后, 2/3地区的冬小麦水分利用效率在逐年提升。农田的破碎化、流转土地经营权不稳定以及农户节水动力和压力不足导致冬小麦节水灌溉普及率不高。面对水粮矛盾, 河北平原仍需加强农业节水, 真正降低蒸散耗水, 才能使其得到缓解。

     

    Abstract: The shortage of water resources and long-term high-intensity agricultural production have further intensified the water crisis in the Hebei Plain, an important grain production region. The local government has implemented a limiting groundwater exploitation policy since 2014 to alleviate the contradiction between water and food security. Measures such as seasonal fallow, rain-fed agriculture, and water-saving agriculture have been implemented in terms of agricultural production. To explore the impact of this policy on agricultural water use, the changes in planting area and water consumption characteristics for winter wheat in the Hebei Plain during the years before and after the implementation of the policy were analyzed. Based on the spectral variation characteristics of winter wheat, distribution maps of winter wheat from 2009 to 2019 were retrieved using MODIS NDVI data. Combined with the TSEB (two-source energy balance model) evapotranspiration dataset and agricultural production statistics, the water consumption characteristics of winter wheat before and after the policy were compared, and the driving factors for these changes were investigated. Our study found that the planting area of winter wheat in the Hebei Plain increased by 183 700 hm2 from 2009 to 2019. Five years after the implementation of the policy, the total planting area of winter wheat increased by 104 000 hm2, mainly concentrated in the east; while it decreased in the west. In terms of water consumption of winter wheat, the level of evapotranspiration and total water consumption of winter wheat increased by 32.58 mm and 1.09 billion m3 compared with those before the policy. Compared with the winter wheat field, seasonal fallow land reduced evapotranspiration by 73 mm in addition to not pumping groundwater for irrigation. During the study period, the annual average water use efficiency of winter wheat was 1.67 kg∙m3. After the implementation of the policy, the water use efficiency of winter wheat in 2/3 regions of the Hebei Plain had been increasing annually. The main reason for the decrease in winter wheat area was the change in planting structure caused by farmers’ pursuit of higher agricultural economic benefits and urbanization. The support policy from the government to ensure food security and improve the mechanization degree of winter wheat planting promoted an increase in its planting area. The fragmentation of farmland, the unstable transfer of farmland management rights, and the lack of initiative and pressure to save water led to the low popularity of water-saving irrigation for winter wheat. Facing the contradiction between water shortage and food production, it is still necessary to strengthen water-saving agriculture and significantly reduce the water consumption of evapotranspiration to alleviate the contradiction.

     

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