华北平原典型井灌区农田水循环过程研究回顾

Agro-ecosystems water cycles of the typical irrigated farmland in the North China Plain

本文回顾了中国科学院栾城农业生态系统试验站在农田水分循环和水量转化方面的研究工作和进展。目前,对于冬小麦-夏玉米农田的蒸散耗水量及其结构(植物蒸腾和土壤蒸发)有较详细的研究结果。全年总蒸散量多年平均870 mm,每年亏缺的350 mm左右需要靠提取地下水保证;同位素分析结果显示土壤蒸发的深度在地表下20 cm处,而植物蒸腾耗水也主要是利用0-40 cm土层的土壤水分。对于土壤深层渗漏量和地下水接受垂直补给的问题,不同研究结果间仍然存在较大差异,尚需更精细的试验来确定。对于区域水量平衡和地下水资源可持续性的评价和管理,目前急需重点开展区域蒸散量的精确估算和模拟研究,以及不同土地利用和不同农业种植方式的水量平衡与水分转化过程研究。

This paper reviewed the research progresses on hydrological cycles and water transformation studies at Luancheng Agro-Ecosystem Experimental Station,Chinese Academy of Sciences（simplified as Luancheng Station） during the past 30 years.As a mostly achieved progress,the evapotranspiration（ET） and its partitioning over irrigated winter wheat-summer maize cropland,which is the most common cultivation pattern in North China Plain,are clarified through multi-years observations using weighing lysimeter,micrometeorological measurements,and isotopic analysis.The annual ET of the irrigated wheat-maize field can reach to 870 mm·a-1,which exceeds the annual precipitation by around 350 mm at an average level.This gap between annual ET and precipitation is bridged by groundwater pumpage.As a matter of long-term over exploitation,the groundwater over the North China Plain experienced rapid depletion and caused wide concerns on sustainability.The study at Luancheng Station suggests that the soil evaporation shares about 1/3 of the total water consumption and the evaporation depth can reach deep to 20 cm under land surface through a isotopic method.Moreover,wheat transpiration is mainly dependent on the soil moisture in the depth of 0-40 cm soil layer,which is largely shallower than the generally used ＂planing wetting depth＂,i.e.100 cm.As for the deep percolation or drainage of the soil water and the vertical recharge rate of groundwater,there exists large range among different studies with different method,such as soil water balance model-ing,rainfall-infiltration experiment,etc.It is urgently needed to go to the details of water cycles over different agricultural land uses and soil properties,and to address the spatial heterogeneities in evapotranspiration,infiltration,and soil water balancing,over the plain.