利用改进的Loheide方法计算地下水的蒸散发量

Quantifying groundwater evapotranspiration by the modified loheide method

在干旱—半干旱地区,地下水的蒸散发是最重要的排泄方式之一,提高其计算精度对准确评价地下水资源具有重要意义。目前在已有的利用地下水水位的昼夜波动计算蒸散发的方法中,Loheide方法是计算精度最高并可以计算小时尺度的方法。针对该方法对水位去趋势化的不足,提出了新的潜水位去趋势的方法,即对3~5天的地下水位采用线性或三次多项式去趋势。采用数值模拟方法,对改进效果进行定量评估。结果表明,当相邻两天的水位变化较大时,提出的去趋势化方法使得蒸散发的计算精度有所提高,其中三次多项式去趋势化方法精度最高,比传统方法精度提高了16%,并且相对于Loheide利用1天数据线性去趋势化的方法,3~5天长序列去趋势能够提高去趋势处理的计算效率。

In arid and semi-arid regions,groundwater evapotranspiration is one of the main discharges,therefore the accurate estimation of evapotranspiration is significant to groundwater resources assessments. The Loheide method is currently the most accurate method to estimate hourly groundwater evapotranspiration using diurnal water table fluctuations. Aiming to improve the detrend procedure,the linear and cubic polynomial detrend method were proposed to detrend water table data over 3 ~ 5 days. The performance of the modification was assessed quantitatively using a model. The results indicate that the linear and cubic polynomial detrend method improve the estimation to some extent for the cases that water table varies dramatically. The best method is the cubic polynomial detrend method that increases the estimation by 16% in comparison to the original detrend method. Compared to the method which uses one-day water table data to get the detrend fluctuation,the modified method also is characterized by the enhancement of the detrend efficiency.