Crop production and agricultural water consumption in the Beijing-Tianjin-Hebei region: History and water-adapting routes

The amount of water resources in the Beijing-Tianjin-Hebei (BTH) region is less than 1% of China, but support approximately 8% of the national population produces 10% of gross domestic product (GDP). Water shortages and groundwater overexploitation are key constraints to the sustainable development of the BTH region. Agricultural water use dominates regional water withdrawal, accounting for 70% of all water use, and the irrigation of high-intensity cropping systems has caused notable groundwater depletion over the past several decades. In this study, the historical stage characteristics of agricultural production scale and irrigation expansion were analyzed based on statistical data. Before 1949, irrigated farmland was mainly located in the piedmont plain of the Taihang Mountains for high-value crop production, irrigation scale and water withdrawal were limited. After 1949, electromechanical irrigation wells gradually replaced traditional shallow wells, and irrigation became a conventional measure for crop production. Since the end of the 1970s, a well-irrigated system has covered the BTH region. Groundwater irrigation provided dominant support for stable agricultural production and sustained high yield. The wheat-maize double-cropping system was enhanced. Simultaneously, the production capacity of fruits and vegetables increased rapidly. The output of grain crops increased from 2.1362×10⁷ t to 3.9448×10⁷ t, an increase of 84.7%. Vegetable production increased from 1.0937×10⁷ t to 5.5084×10⁷ t, an increase of 403.6%. The fruit output increased from 1.440×10⁶ t to 1.5052×10⁷ t, with a 945.6% increase. High yields depended on adequate irrigation, and groundwater depletion occurred as a result of a trade-off between water and agricultural products in the BTH region. Over the last four decades, agricultural production in Beijing, Tianjin, and Hebei has diverged in terms of scale and structure. The crop planting areas of Beijing and Tianjin decreased by 85.0% and 38.7%, respectively. Beijing has almost abandoned grain crop production, but the agricultural production capacity of Hebei Province has further increased. In 2018, 93.8% of grains, 99.1% of oilseeds, 92.9% of cotton, 93.1% of vegetables, and 91.7% of fruits in the BTH region were contributed by Hebei Province. This pattern of differentiation intensified the importance of agricultural production in Hebei Province in the BTH region, which has reliably increased the pressure on agricultural production and water withdrawal in Hebei Province. Studies have explored cropping systems that are more sustainable for groundwater sustainability. Based on field experiments and crop models, it was confirmed that reducing planting intensity can help mitigate groundwater decline, and winter wheat has been reported to be the main contributor to groundwater consumption. The cropping system of three harvests over two years has been suggested as a better alternative cropping system for water savings than the current winter wheat-summer maize double cropping system, which could save more water each year with a slight grain yield loss. However, the interaction between grain production capacity and water consumption intensity on medium- and long-term time scales for different water-adapting rotations of crops remains unclear and insufficient. From a policy-making perspective, it is necessary to improve the comprehensive agricultural plan under the conditions of the BTH coordinated development strategy. To ensure regional food security and stable agriculture, the water-adapting transformation of agricultural production in the BTH region should be promoted in an orderly and efficient manner.