A study of the irrigation strategy to maintain winter wheat production and prevent confined groundwater depletion

The most serious area with groundwater over-exploitation of deep aquifers in China is the Heilonggang region of Hebei Province in the North China Plain (NCP), where deep confined aquifers are facing the risk of depletion. However, as an important producer of high-quality winter wheat in China and the main producer in Hebei Province, this region shoulders the important responsibility of ensuring edible grain security in Hebei Province. Thus, banning deep groundwater exploitation and stabilizing winter wheat yield must be taken into account at the regional scale when proposing irrigation strategy for winter wheat. This is urgently needed by the relevant departments in this key implementation area of the comprehensive treatment action plan for groundwater over-exploitation in the NCP. Simulation using the distributed agro-hydrological model and further estimation show that the average amounts of deep groundwater exploitation for winter wheat irrigation under the current irrigation schedule and for other purposes are approximately 9.62×10⁸ m³ and 12.47×10⁸ m³, respectively, in the whole region. Considering that deep groundwater exploitation for domestic and industrial use has been mostly replaced by water diversion from the middle route of the South-to-North Water Diversion (SNWD) project in this region, we propose to further increase the water supplies from the northern extension emergency project of the eastward route of SNWD and from the Yellow River to the Baiyangdian Lake of Hebei Province diversion project to replace the deep groundwater used for winter wheat well irrigation. If the water supplies from these external water diversion projects can meet the demand of 9.62×10⁸ m³ for winter wheat canal irrigation, not only can stable winter wheat production be ensured, but deep groundwater over-exploitation can also be curbed. Water amounts of approximately 8.21×10⁸ m³, 5.47×10⁸ m³ and 2.74×10⁸ m³ from external water diversion projects are required to only meet the demand for irrigation three times, twice and once, respectively, during the winter wheat season, while the total winter wheat yield will be reduced by approximately 8%, 34% and 56%, respectively, compared with the current irrigation schedule. In summary, this study can provide a reference for the relevant departments to plan external water diversion schemes considering the banning of deep groundwater exploitation and the stabilization of winter wheat production.