Exploring the coupling characteristics of regional water resources and food security helps to promote the sustainable development of grain production and is of great significance for achieving global food security. From the aspects of regional “water supply”, “water use” and “water demand”, the coupling characteristics of water resources and food security were systematically revealed; the new challenges faced by regional food security from the perspective of water resources were clarified; and effective ways to promote the utilization of regional water resources and the sustainable development of grain production were explored. This paper took Northwest China, which is the most arid region, where water-resource utilization and food security are in contradiction, as the research area. The water-resource load index, the water footprint of grain production and the water-consumption footprint were used to quantify the regional water-resource pressure index, as well as the residential grain-consumption types, population urbanization, the industrial-grain-processing industry and their corresponding water-consumption footprints from 2000 to 2020. The coupling characteristics of water resources and food security were systematically revealed. The results showed the following: (1) In 2000–2020, the water-resource load index increased from 4.0 to 10.7, and the load level increased from III to I. At the same time, agricultural water resources were largely allocated elsewhere. (2) During the period, the food rations showed a significant decreasing trend, and the average annual reduction was 3.4% (p < 0.01). The water footprint of animal products increased, particularly for beef and poultry (the average annual growth rates were 9.9% and 6.3%, respectively). In addition, the water footprint of industrial food consumption increased by 297.1%. (3) With the improvement of the urbanization level, the water-consumption footprint increased by 85.9%. It is expected that the water footprint of grain consumption will increase by 39.4% and 52.3% by 2030 and 2040, respectively. Exploring how to take effective measures to reduce the water footprint to meet food-security needs is imperative. This study proposed measures to improve the utilization efficiency of blue and green water and reduce gray water and the grain-consumption water footprint from the aspects of regional planting-structure optimization potential, water-saving irrigation technology, dietary-structure transformation and virtual water trade; these measures could better relieve the water-resource pressure and promote the sustainable development of grain production and water-resource utilization.

It is of great significance to systematically analyze the characteristics of the regional grain supply and demand balance, reveal the influence mechanism of crop sustainable development, and put forward effective countermeasures to achieve the goal of food security. This paper aims at addressing the unique geographical characteristics of Northwest China and the current lack of research on its food security. This paper systematically analyzes the temporal and spatial variation characteristics of the regional grain production, consumption and food security level. The main factors affecting regional food security are examined, and we put forward effective suggestions to promote regional sustainable production. The results show that the average annual growth rate of grain production in Northwest China from 2000 to 2021 was 3.4%, and the years of increased grain production accounted for 77.3%. The main reason for the increase in grain production was the increase in yield per unit area (average annual growth of 2.8%), of which the rice yield was the largest, up to 7.3 t/ha. Maize and wheat accounted for 60.7% and 23.4% of the total grain production in the region, respectively. From the perspective of the regional structure, Inner Mongolia contributed the most to the grain production in the region, accounting for 33.5% of the total output. Xinjiang, Shanxi, Shaanxi, Gansu, Ningxia and Qinghai contributed 17.1%, 15.4%, 15.2%, 13.0%, 4.5% and 1.3%, respectively, to grain production. From the perspective of the dietary structure, the grain consumption pattern in Northwest China has gradually changed from raw grains to animal products, which has undoubtedly increased the regional demand for grain. At present, since the increase in output is greater than the demand for food, the food self-sufficiency rate in the region has increased from 0.81 to 1.28. Since the grain yield per unit area in Xinjiang and Ningxia has a relative advantage over other provinces, to achieve regional food security for a long time, moderately increasing the grain planting area in these two provinces will help to promote regional food security. In addition, as the grains produced in the region are mainly wheat and corn, the yield level of wheat and corn in Xinjiang and Qinghai has a comparative advantage within Northwest China. Therefore, moderately increasing the planting area of wheat and corn in Xinjiang and Qinghai is of great significance in ensuring regional food security. The research results can provide theoretical support for the realization of regional food security and provide a reference for other regions in the world, to better serve global food security.

From the perspective of water resources, revealing the potential of sustainable production of crops, clarifying the obstacles, and taking effective measures in advance can not only provide residents with long-term sufficient and nutritious food needs but also help to promote food security and economic benefits. Previous studies on this aspect have mainly focused on food crops and paid less attention to cash crops. This study takes Northwest China as the research area, which is a typical arid and semi-arid region with the most prominent contradiction between water supply and demand. We analyzed the changing characteristics of the available water resources, the production water footprint, and the total water footprint over time from the perspective of water resources, and systematically analyze the potential for sustainable development. The results showed that the regional water resource consumption in 2000–2020 showed a significant upward trend (p < 0.01). Similarly, the water resource load index also increased in this period, which increased by 164.3%. Water resources pressure increased from level III to level I, and there is no further development potential. At the same time, the proportion of available agricultural water resources was forcibly reduced by 9.0%. Fortunately, the crop production water footprint showed a significant decreasing trend (p < 0.01), with a decrease of 43.6%. Among them, grain and cash crops decreased by 45.4% and 49.5% respectively. Although the production water footprint is reduced, regional production is increasing to meet the increasing consumer demand. The crop water footprint showed a significant increase (p < 0.01), increasing by 13.4%. The available water resources of crops in the region are compressed, but the amount of water needed for crop production is increasing significantly, which poses challenges to the sustainable production of crops. According to the research results, the detailed recommended measures to promote sustainable regional crop production are put forward from the perspective of increasing the amount of regional water resources available, improving the utilization efficiency of blue and green water, and crop yield level, so as to better serve the global food security.

Exploring the mechanisms of competition for water resources in the regional food and energy industries,taking effective countermeasures in advance will help to promote the sustainable development of the regional food and energy industries. Based on the theory of water footprint, this paper quantifies the water footprint of grain and energy in Shanxi Province, China, and the competition index of energy-grain industry to water resources. Through the ratio of grain blue water and energy water footprint to total water consumption in the region, this study coupled the characteristics of their proportional changes to obtain a competition index that can characterize the competition relationship between regional food and energy industries for water resources. The results showed that (1) In 2000–2021, although the grain yield increased by 81.1%, the grain water footprint only increased by 11.2%, with an average annual growth of 1.0%. The proportion of blue, green and gray water footprints changed from 14.1%, 54.3% and 31.6% in 2000 to 18.8%, 41.2% and 39.9% in 2021, respectively. (2) The energy water footprint increased at an average annual rate of 10.8%, an increase of 544.7% over the period. The coal, natural gas and thermal water footprints in 2021 have increased by a factor of 2.7, 109.2 and 4.0, respectively, compared to 2000. Coal’s share of the energy water footprint is 70.6%. (3) The average value of the food and energy industry’s competition index for water resources is 0.77, increasing from 0.42 in 2000 to 0.94 in 2021, an average annual increase of 4.3%. These results show that the future sustainable development of the region is facing the major challenge. Therefore, from the perspective of reducing the demand for crop and energy water footprint, some suggestions are put forward to effectively promote the healthy development of the region.