旱区农业灌溉用水反弹效应及其区域差异——以西北五省(区)为例

Estimation,driving factors,and regional differences of agricultural irrigation water rebound effect in arid areas:Examples of five provinces in northwestern China

在干旱半干旱地区,农业部门用水量大,但利用率不高,所以发展节水灌溉成为缓解水资源稀缺的可能路径。但是在节水灌溉技术提高的条件下,如果实际节水效果达不到预期,就会出现"灌溉用水反弹效应"。基于此,本文从理论上构建了灌溉用水反弹效应的衡量方法,然后利用LMDI分解法将灌溉用水反弹效应分解为气候效应、单产效应、结构效应、面积效应和灌溉效应,并利用西北五省(区)2005—2016年的数据,在效应测算和分解的基础上分析了其驱动因素及区域差异。结果发现:(1)西北五省(区)整体的反弹效应高达340.00%,即新增用水量达到了预期节水量的3.4倍,其中甘肃、宁夏、青海、陕西和新疆的灌溉用水反弹效应分别为374.97%、55.10%、117.46%、434.51%和384.32%;(2)单位面积产量增长和种植面积扩大始终是促进西北整体和各省(区)灌溉用水反弹效应上升的驱动因素;(3)西北整体灌溉用水反弹效应上升的主导因素为单位面积产量增长,但各省(区)存在区域差异,其中甘肃、宁夏和陕西为单位面积产量增长,青海为气候变化,新疆为种植面积扩大。所以,为缓解旱区农业灌溉用水反弹效应,在整体策略上,不能追求单产的最大化,而应适当采取亏缺灌溉,并合理规划灌溉农业规模;在局部策略上,要实行差异化的区域政策,因地制宜。

In arid and semi-arid regions,the agricultural sector uses a lot of water,but the utilization rate is not high.Therefore,the development of water-saving irrigation has become a possible way to alleviate the scarcity of water resources.However,under the conditions of improved water-saving irrigation technology,if the actual water-saving effect fails to meet expectations,the“irrigation water rebound effect”will appear.Based on this situation,this paper theoretically constructs a method for measuring the irrigation water rebound effect,and then uses the LMDI method to decompose the irrigation water rebound effect into climate effect,unit yield effect,structural effect,area effect and irrigation effect.And,with the data of five northwestern provinces from 2005 to 2016,based on the calculation and decomposition of the effect,this paper analyses the driving factors and regional differences of agricultural irrigation water rebound effect in arid areas.The results show that:(1)The overall rebound effect in the northwest of China is as high as 340.00%,that is,the newly added water use has reached 3.4 times the expected water saving.Among them,the irrigation water rebound effects in Gansu,Ningxia,Qinghai,Shaanxi and Xinjiang are 374.97%,55.10%,117.46%,434.51%,and 384.32%,respectively.(2)The increase in output per unit area and expansion of planting area are always the driving factors that promote the increase in the irrigation water rebound effect in the entire northwest or the provinces.(3)The increase in output per unit area is the main driving factor for increase in the overall irrigation water rebound effect in the northwest.However,there are still regional differences among the northwestern provinces.Among them,the main driving factors in Gansu,Ningxia,and Shaanxi are the increase in output per unit area,while the main driving factors in Qinghai and Xinjiang are the climate change and expansion of planting area,respectively.Based on these results,in order to avoid the agricultural irrigation water rebound effect in arid and semiarid regions,the overall strategy should not be to pursue the maximization of yield.Deficit irrigation should be appropriately adopted instead,and the scale of irrigated agriculture should be rationally planned.In terms of local strategies,regionalized policies should be adapted based on local conditions.