Water Distribution in an Arid Zone Soil: Numerical Analysis of Data from a Large Weighing Lysimeter
Water Distribution in an Arid Zone Soil: Numerical Analysis of Data from a Large Weighing Lysimeter
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DOI：
10.2136/vzj2017.01.0035
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发表时间：
2018-05-17
影响因子：
2.8
通讯作者：
van Genuchten, M. Th
中科院分区：
文献类型：
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作者：
Dijkema, J.;Koonce, J. E.;van Genuchten, M. Th
虽然沙漠土壤覆盖了地球陆地表面的大约三分之一，但令人惊讶的是，人们对它们的物理特性以及这些特性如何影响干旱环境的生态和水文学知之甚少。这项研究的主要目的是提高我们对沙漠土壤水动力学的认识。为此，我们开发了一个基于过程的组件内HYDRUS-1D描述干旱区土壤的水分动态作为通过土壤表面的水通量的函数。为更好地描述土壤水分特征曲线干端的基本流动过程，提出了一种改进的货车van Schlichten模型。进一步使用缩放方法来解释由于体积密度与深度的变化而引起的保水性的变化。该模型进行了校准和验证，使用每小时的土壤水分，温度和质量数据从3米深的称重蒸渗仪在非均质干旱土壤设施的缩放环境过程在沙漠研究所（拉斯维加斯，内华达州）。测量和模拟在1年期间同意更好的降水（湿润）比蒸发（干燥）条件下。蒸发是更好地模拟湿润比干燥的土壤表面条件。这可能是由于与大气的汽相交换过程造成的，这一过程没有得到解释，需要进一步探讨。总体而言，该模型提供了一个有前途的第一步，发展一个更现实的数值工具，量化干旱生态系统的水分动态及其在气候变化，植物生长，侵蚀和补给模式的作用。
Although desert soils cover approximately one third of the Earth's land surface, surprisingly little is known about their physical properties and how those properties affect the ecology and hydrology of arid environments. The main goal of this study was to advance our understanding of desert soil hydrodynamics. For this purpose, we developed a process-based component within HYDRUS-1D to describe the moisture dynamics of an arid zone soil as a function of water fluxes through the soil surface. A modified van Genuchten model for the dry end of the soil water retention curve was developed to better capture the basic flow processes for very dry conditions. A scaling method was further used to account for variabilities in water retention because of changes in the bulk density vs. depth. The model was calibrated and validated using hourly soil moisture, temperature, and mass data from a 3-m-deep weighing lysimeter of the Scaling Environmental Processes in Heterogeneous Arid Soils facility at the Desert Research Institute (Las Vegas, NV). Measurements and simulations during a 1-yr period agreed better under precipitation (wetting) than under evaporation (drying) conditions. Evaporation was better simulated for wet than for dry soil surface conditions. This was probably caused by vapor-phase exchange processes with the atmosphere, which were unaccounted for and need to be further explored. Overall, the model provides a promising first step toward developing a more realistic numerical tool to quantify the moisture dynamics of arid ecosystems and their role in climate change, plant growth, erosion, and recharge patterns.