Monitoring Temporal Development of Spatial Soil Water Content Variation
Monitoring Temporal Development of Spatial Soil Water Content Variation
复制标题
土壤含水量空间变化的时间发展监测
DOI：
10.2113/2.4.519
复制
发表时间：
2003
影响因子：
2.8
通讯作者：
G. Heuvelink
中科院分区：
文献类型：
--
作者：
J. Huisman;J. Snepvangers;W. Bouten;G. Heuvelink
我们比较探地雷达 (GPR) 和时域反射计 (TDR) 评估地表体积含水量空间变化的时间发展的能力。就探地雷达而言，我们使用地波测量地表水含量，地波是发送器和接收器之间穿过土壤上层厘米的直接波。在30天的监测期内，利用GPR和TDR测量了18天的空间含水量变化。为了确保空间含水量变化的较大波动，我们通过2天的灌溉创建了含水量的异质模式。通过变差函数和插值含水量图研究了空间变化的时间发展。为了比较 GPR 和 TDR 变差函数，我们使用折刀法和模型参数不确定性的一阶近似估计了实验变差函数和变差函数模型参数的置信区间。结果表明，由于探地雷达测量次数较多，探地雷达实验变差函数的 95% 置信区间比 TDR 实验变差函数的 95% 置信区间小一到两个数量级。因此，GPR 变差函数模型参数的不确定性也低得多，这意味着拟合 GPR 变差函数模型参数的时间发展更容易解释。此外，较大的 GPR 测量体积导致 1 × 10−6 至 1 × 10−9 (m3 m−3)2 的低空间块金方差，因为短距离变化是平均的。这意味着即使在含水量变化较小的情况下，探地雷达也能准确测量空间相关长度。对于探地雷达来说，插值图显示由于灌溉而导致水含量增加以及随后土壤逐渐干燥的情况更加准确和可重复。结论是，非侵入性探地雷达测量提供了准确、一致地及时监测空间含水量变化发展的手段。
We compare the capability of ground penetrating radar (GPR) and time domain reflectometry (TDR) to assess the temporal development of spatial variation of surface volumetric water content. In the case of GPR, we measured surface water content with the ground wave, which is a direct wave between the sender and receiver through the upper centimeters of the soil. Spatial water content variation was measured on 18 d with GPR and TDR during a 30-d monitoring period. To ensure large fluctuations in the spatial water content variation, we created a heterogeneous pattern of water content by irrigation on 2 d. The temporal development of the spatial variation was studied by means of the variogram and interpolated water content maps. To compare GPR and TDR variograms, we estimated confidence intervals of the experimental variograms and the variogram model parameters with a jackknife approach and a first-order approximation of model parameter uncertainty. The results showed that the 95% confidence intervals of the GPR experimental variogram were one to two orders of magnitude smaller than the 95% confidence intervals of the TDR experimental variogram because of the larger number of GPR measurements. Consequently, the uncertainty in the variogram model parameters was also much lower for GPR, which meant that the temporal development of the fitted GPR variogram model parameters was easier to interpret. Furthermore, the larger GPR measurement volume resulted in a low spatial nugget variance of 1 × 10−6 to 1 × 10−9 (m3 m−3)2 because short distance variation was averaged. This meant that GPR accurately measured spatial correlation lengths, even in the case of low water content variation. Interpolated maps showing the increase of water content due to irrigation and the subsequent gradual drying of the soil were more accurate and reproducible for GPR. It was concluded that the noninvasive GPR measurements provide the means to accurately and consistently monitor the development of spatial water content variation in time.