Establishing water-adaptive cropping systems to combat aquifer depletion in North China

Groundwater exploitation has facilitated the strengthening of world food security as populations have rapidly grown, but preventing overexploitation is a major challenge. North China has one of the world's largest groundwater depression cones due to its average annual groundwater overdraft of nearly 9.0 ​km³. To achieve a balance between extraction and recharge of aquifers, groundwater use by agriculture must be reduced by 4.746 ​km³ annually, alongside water diversion. In order to explore the sustainability of agricultural development in the context of reduced groundwater extraction in North China, which does not jeopardize Chinese food security, is economically feasible, and socially recognized, we selected 10 water-saving planting schemes and 2 scenarios (whether or not to replace surface irrigation with drip irrigation for vegetables and fruit trees) based on multi-source data including the area where water-saving alternatives can be implemented, big data from crop water-saving field trials such as the irrigation quotas, water consumption, and yield, water-saving subsidies from the government, and local costs and prices of crop production from an actual survey, and expected to obtain the optimization schemes of sustainable water-adaptive cropping systems matching with water availability. We obtained the feasible water-adaptive cropping solutions to address the groundwater overexploitation in North China, i.e. the annual winter wheat–summer maize double cropping system should be maintained rather than the annual single cropping system or afforestation; drip irrigation (a water-saving irrigation method) should be applied to all fields of vegetables and fruit trees; limited irrigation (a water-saving irrigation regime) of winter wheat in well-irrigation regions should be implemented (for example, one irrigation event across 50 ​% of the area or two events over 100 ​% rather than three irrigation events); and cotton planting (a water-saving cropping system) should be appropriately increased by replacing winter wheat. These adaptations will keep the increase in net income of farmers without decreasing and the total water-saving subsidies payable by the Chinese government to below 10 ​× ​10⁹ Chinese Yuan while resulting in an annual loss of the national wheat and/or maize production of less than 5 ​%.