Watershed‐Scale Effective Hydraulic Properties of the Continental United States
Watershed‐Scale Effective Hydraulic Properties of the Continental United States
复制标题
DOI：
10.1029/2020ms002440
复制
发表时间：
2021-06
影响因子：
6.8
通讯作者：
A. Tashie;T. Pavelsky;L. Band;S. Topp
中科院分区：
文献类型：
--
作者：
A. Tashie;T. Pavelsky;L. Band;S. Topp
在陆地表面模型（LSMs）中，地下的水力特性通常是根据地球表面土壤的质地来估计的。这种方法忽略了大孔隙、裂缝流动、非均质性以及地下水的可变分布对有效流域尺度水力变量的影响。利用水文曲线衰退分析，我们对美国所有参考流域的流域尺度有效水力导率(K)和有效可排水含水层储存量(S)进行了经验约束估算，这些流域有足够的流量数据可用（n = 1561）。然后，我们使用机器学习方法对整个美国的这些属性进行建模。模型验证结果对log(K)的估计有很高的置信度（r2 > 0.89; 1% 0.83; - 70% < bias < - 18%）。我们对有效钾的估计平均比基于土壤质地的平均钾估计高两个数量级，证实了土壤结构和流域尺度上优先流动路径的重要性。我们对有效S的估计与最近全球对流动地下水的估计比较有利，并且在空间上是不均匀的（5-3,355 mm）。由于S的估定值远低于lsm中通常使用的全局最大值（例如，Noah‐MP中的5,000 mm），因此它们既可以限制模型自旋启动时间，也可以将模型参数约束为更现实的值。这些结果代表了首次尝试约束流域尺度有效水力变量的估计，这些变量是在整个美国相邻地区实施lsm所必需的。
In land surface models (LSMs), the hydraulic properties of the subsurface are commonly estimated according to the texture of soils at the Earth's surface. This approach ignores macropores, fracture flow, heterogeneity, and the effects of variable distribution of water in the subsurface on effective watershed‐scale hydraulic variables. Using hydrograph recession analysis, we empirically constrain estimates of watershed‐scale effective hydraulic conductivities (K) and effective drainable aquifer storages (S) of all reference watersheds in the conterminous United States for which sufficient streamflow data are available (n = 1,561). Then, we use machine learning methods to model these properties across the entire conterminous United States. Model validation results in high confidence for estimates of log(K) (r2 > 0.89; 1% 0.83; −70% < bias < −18%). Our estimates of effective K are, on average, two orders of magnitude higher than comparable soil‐texture‐based estimates of average K, confirming the importance of soil structure and preferential flow pathways at the watershed scale. Our estimates of effective S compare favorably with recent global estimates of mobile groundwater and are spatially heterogeneous (5–3,355 mm). Because estimates of S are much lower than the global maximums generally used in LSMs (e.g., 5,000 mm in Noah‐MP), they may serve both to limit model spin‐up time and to constrain model parameters to more realistic values. These results represent the first attempt to constrain estimates of watershed‐scale effective hydraulic variables that are necessary for the implementation of LSMs for the entire conterminous United States.