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在以往的蒸渗仪使用中发现，由于大气压在不同季节以及一天中不同时间均有变化，从而引起蒸渗仪观测值的相应变化，其变化幅度为００４～１００ｍｍ。在第三代蒸渗仪的研制中，在地下水位线上设计了排水管，有效地消除了这种影响。此外，由于冻土层以下形成一个由上而下的土壤温度梯度，引起贮水层的水分向上运动而集结于冻土层，冻土层下发生的这种水汽热运动现象被称为“假蒸散”现象，此现象１２月份出现，次年３月消失。地下水位越深，“假蒸散”值越小，可用水分平衡方程（Ｅ＝Ｉ＋Ｐ＋Ｗ１－Ｗ２－Ｄ）来测算实际“蒸散”值。
In the past use of lysimeter found that due to atmospheric pressure in different seasons and at different times of the day have changed, which led to the corresponding changes in the observed values of the lysimeter, the range of change of 0 04 ~ 1 00mm. In the development of the third generation of lysimeter, a drainage pipe was designed on the groundwater level, effectively eliminating this effect. In addition, the thermal movement of water vapor occurring under the permafrost is called “fake” due to the formation of a top-down soil temperature gradient below the permafrost that causes the water in the aquifer to move upwards and build up in the frozen soil layer Evapotranspiration “phenomenon, which appeared in December and disappeared in March the following year. The deeper the groundwater table is, the smaller the value of ”pseudo-evapotranspiration“ is. The actual ”evapotranspiration" can be calculated by the equation of water balance (E = I + P + W1-W2-D)