新型蒸渗仪及其在农田水文过程研究中的应用

A new large weighing lysimeter and its application to agro\|hydrological process studies

一台用于测定农田蒸腾蒸发和地下水—土壤水转化的新型称重式蒸渗仪在中国科学院禹城试验站建造完成,并连续数年成功运行.新型蒸渗仪主要有以下特点:(1)蒸渗仪精度0016mm,可同时准确测量蒸腾蒸发量和地下水对土壤水的补给量与入渗量;(2)蒸渗仪面积314m2,深度5m,充分允许农作物根系发育与吸水、土壤水和地下水水分转化、地下水位变化等过程的进行,可以较好的代表大田的情形;(3)蒸渗仪的供排水系统能够在蒸渗仪内模拟实际地下水位变化;(4)土柱重30～34Mg,包含非饱和与饱和土壤,土壤质地以粉沙和轻壤为主.自1998年10月至1999年6月冬小麦生长期蒸渗仪运行结果表明:在冬小麦生长期,当地下水在16～24m变动时地下水对土壤水的补给量约占总蒸腾蒸发量的166%.过多的灌溉量不仅削弱了地下水对土壤水的补给,而且多余的灌溉水下渗补给地下水.

A large weighing lysimeter is installed at Yucheng Comprehensive Experimental Station for agro\|hydrological studies.Features of the lysimeter include the following:1\^Mass resolution equivalent to 0\^016mm of water to accurately determine hourly evapotranspiration,groundwater evaporation and groundwater recharge simultaneously;2\^A surface area of 3\^14m\+2 and a soil profile depth of 5\^0m to permit normal plant development,soil water extraction,soil water/groundwater exchanges and fluctuations of groundwater level;3\^A special supply\|drainage system to simulate field conditions of groundwater within the lysimeter,4\^A soil mass of about 30Mg including both unsaturated and saturated loam.The soil mainly consists of mealy sand and light loam.The monitoring data indicate that during the growing period of winter wheat groundwater contributes 16\^6% of total evapotranspiration for water\|table depth from 1\^6m to 2\^4m below ground surface.Excess irrigation reduces the amount of upward water flow from groundwater table and causes deep percolation to groundwater.