对既保冬小麦产量又防承压水耗竭的灌溉策略之探讨

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

我国深层地下水超采最严重的区域当属华北平原的河北省黑龙港地区,该区域的深层承压含水层面临枯竭的安全风险。然而,黑龙港地区作为我国优质冬小麦的重要产区和河北省冬小麦的主产区,肩负着河北省确保冬小麦这一重要口粮稳产的责任。因此,冬小麦生育期的灌溉策略必须在区域尺度上兼顾深层地下水的禁采和冬小麦产量的稳定,这也是当前黑龙港地区这个“华北平原地下水超采综合治理行动方案”重点实施区域的有关部门所亟需的。本文基于分布式农业水文模型的模拟研究及进一步的估算,表明:就黑龙港地区整体而言,在现状灌溉情形下冬小麦生育期多年平均所用的深层地下水开采量和其他用途的深层地下水开采量分别约为9.62×10^(8) m^(3)和12.47×10^(8) m^(3)。考虑到该区域生活和工业所用的深层地下水开采量目前大多已被南水北调中线工程的引水所置换,我们建议:进一步增加“南水北调东线一期工程北延应急供水工程”和“引黄入冀补淀工程”置换黑龙港地区冬小麦井灌所用深层地下水的水量,以满足外调引水9.62×10^(8) m^(3)用于冬小麦生育期进行渠灌的需求,如此才能既确保该地区冬小麦稳产又遏制深层地下水的超采态势。若外调引水量只可以分别满足在冬小麦生育期灌水3次、2次和1次的灌溉定额,则每年在冬小麦生育期所需的外调引水量分别约为8.21×10^(8) m^(3)、5.47×10^(8) m^(3)和2.74×10^(8) m^(3)。然而,与现状灌溉情形相比,冬小麦总产将分别减少约8%、34%和56%。总之,本研究可为相关部门就兼顾禁采深层地下水与稳定冬小麦产量而规划外调引水方案提供一定的参考。

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 9.62×10^(8) m^(3) and 12.47×10^(8) m^(3),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 9.62×10^(8) m^(3) 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 8.21×10^(8) m^(3),5.47×10^(8) m^(3) and 2.74×10^(8) m^(3) 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.