估算干旱区地下水依赖型植物蒸散发的White法评述

日尺度上的地下水位波动是干旱区地下水依赖型植物蒸散消耗地下水的直接证据与指示。White通过分析日尺度地下水位波动与植被蒸散之间的关系,提出了利用地下水位观测数据来计算植被蒸散速率的方法,简称White法。该方法由于计算简单,所需数据少,在干旱区河岸林蒸散定量方面得到了广泛的应用。本文通过系统回顾White法的提出、“四大假设条件”及其在实际应用中的不足,梳理了近年来对White法不断修订的总体思路,总结了各种形式White法的特点、使用条件以及存在的主要问题;在此基础上,提出了White法进一步改进的方向。当前,结合地表蒸散发的多尺度观测与模拟,White法不仅可以用来估算区域尺度地下水蒸散,而且能够为定量解析干旱区植物的水分利用来源提供验证与参考。

A review of the White method for the estimation of evapotranspiration from phreatophytes in arid areas

Diurnal water table fluctuation is considered the evidence and indicator of groundwater evapotranspiration by phreatophytes in arid areas. Based on the relationship between plant evapotranspiration and diurnal water table fluctuation, White proposed an analytical solution for estimating evapotranspiration rates using groundwater level monitoring data, i.e., the White method. Due to its simplicity and limited data requirements, this method has been widely used to estimate plant evapotranspiration in riparian zones of arid areas. In this article, we first introduced the fundamentals and four assumptions of the White method, and uncertainties that are involved in its application. Then, we reviewed the recent developments in the method, and discussed the main characteristics, limitations, and shortcomings of each modification; on this basis, the principle of further improvement of the White method is proposed. At present, combined with multi-scale observation and simulation of land surface evapotranspiration, the White method can be used not only to estimate regional scale groundwater evapotranspiration, but also to provide a reference for investigating water sources for plant use in arid regions.