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Abstract:The North China District (NCD) is one of the main grain production regions in China. The double cropping system of irrigation has been leading to the groundwater table decline at the speed of 1-2 m per year. Climate change leads to uncertainty surrounding the future of the NCD agricultural system, which will have great effects on crop yields and crop water demands. In this research, the Meteorological dataset from 54 weather station sites over the period 1960-2015 were collected to quantify the long-term spatial and temporal trends of meteorological data, including daily minimum temperature (T min ), maximum temperature (T max ), precipitation, solar radiation, reference evapotranspiration (ET 0 ), and aridity index (AI). The results show that the long-term wheat and maize growing season and annual average air temperatures (T min and T max ) showed strong north to south increasing trends throughout the NCD. The average annual precipitation was 632.9 mm across the NCD, more than 70% of which was concentrated in the maize growing season. The regional average annual ET 0 was 1026.1 mm, which was 531.2 and 497.4 mm for the wheat and maize growing season, respectively. The regional precipitation decreased from northwest to southeast in each growing season and annual timescale. The funnel areas have lower precipitation and higher ET 0 than the regional average, which may lead to the mining of the groundwater funnel area. The regional average annual AI is 0.63, which lies in the humid class. For temporal analysis, the regional average trends in annual T min , T max , solar radiation, ET 0 , precipitation, and AI were 0.37 • C/10a, 0.15 • C/10a, −0.28 MJ/day/m 2 /10a, −2.98 mm/10a, −12.04 mm/10a, and 0.005/10a, respectively. The increasing trend of temperature and the decreasing trend of solar radiation may have a negative effect on the regional food security. The funnel area AI showed a significant increasing trend for the winter wheat growing season and a decreasing trend for maize, which indicated that more irrigation will be needed for the maize growing season and the winter fallow policy may lead to the increasing trend precipitation being wasted. Analyzing the growing season and the annual meteorological elements of the spatiotemporal trends can help us better understand the influence of climate change on the natural resources and agricultural development in both the past and the future, and will provide us with invaluable information for the modification of cropping patterns to protect the regional and national water and food security.

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Water resources are the largest limiting factors for wheat (Triticum aestivum L.) production in the North China Plain (NCP). Irrigation used in wheat production has caused a reduction in the groundwater table and aggravated regional water scarcity. In this research, we analyzed the spatiotemporal changes in winter wheat cropping area and water balance during the winter wheat growing season in the groundwater overexploitation district (GOD) from 1985 to 2015. Focusing on typical districts, we set different optimized cropping scenes and estimated water‐saving potential based on current national policy (fallow planting area and reduce irrigation events). The winter wheat area increased in the GOD during the past 30 yr, especially in deep overexploitation area (DOA). There was a slight decrease in shallow overexploitation area (SOA) but a slight increase in the mixed area (MA). The winter wheat area was more concentrated in DOA during the past 30 yr. Lower precipitation, higher crop evapotranspiration (ETc), and higher evapotranspiration of applied water (ETaw) occurred in the GOD than in other areas in the NCP. We set optimized planting scenes that fallow 10% cultivated area in DOA and 5% in MA while reducing one irrigation event in the whole area. Results showed that the water‐saving potential in GOD could reach 14.09 billion m3 with 4.54 Tg yield lost. This research can help us better understand the influence of winter wheat production on groundwater overexploitation and is useful for the government to develop and extend ongoing adaptation strategies for coping with groundwater overexploitation events.

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