CRNS and root zone soil moisture dynamics in agricultural land

该项目的重点是GW在研究单位宇宙意义第一阶段所做的工作，主要涉及利用CRNS估算地下水补给，以及土壤水分剖面形状对CRNS解释的影响。利用一维包气带模型可以估计逐日的田间尺度补给率，并测试了几种将CRN集成到这种模型中的方法。在第二阶段中，关于不同垂直土壤水分分布对传感器信号产生和穿透深度的影响的研究将扩展到接近自然条件的高度管理系统，主要用于农业用地。为了实现这一点，将对CRNS测量进行评估(如果已经存在)，或者在CRNS渗透深度内受浅层地下水影响的不同田间地点进行CRNS测量，或者通过专门的作物田人工喷灌试验进行CRNS测量。土壤水分垂直分布的这种大带宽将成为系统评估与农业应用有关的CRNS渗透深度的基础。对根际土壤剖面内水分的垂直非均匀分布和CRNS可变渗透深度的基本了解，将使我们能够基于CRNS测量，更全面地了解根际土壤区域的水分储存和通量，例如，在地下水位和排水条件受到控制的田间地点。因此，应把更大的重点放在CRN和植物-土壤相互作用上，从而使植被的根系作为驱动储水量的变化，对干旱后深层土壤的补给和地下水补给起决定性作用。此外，它们本身也可能受到水分胁迫和创造灌溉需求的影响，其管理可以通过基于CRNS的测量或建模来支持。土壤水分剖面的测量和模拟及其对CRNS渗透深度的影响不仅对本项目，而且对研究单位内的其他项目都是必要的，因为它是估计整个根区水分通量和水平衡计算的基础。例如，由此产生的土壤水分剖面将被纳入水文大地测量的深度尺度方法，将支持区域化努力，并更好地约束CRN测量的雪水当量。此外，我们将在小流域尺度上与其他研究模块一起定义用于测试CRNS解释、辐射传输模型和水文重力方法的合成土壤水分数据集，并将负责其整体组织。

The focus of this project builds on work done in GW in the first phase of the research unit Cosmic Sense which has mainly dealt with the use of CRNS for estimating groundwater recharge and the influence of soil moisture profile shape on CRNS interpretation. Field scale recharge rates at daily basis could be estimated by the use of 1D vadose zone models, and several ways to integrate CRNS within such models were tested. Accompanying measurements were designed and a simple approach developed to compensate for the vertically decreasing sensitivity of the sensor in respect to heterogeneous soil moisture profiles.Within the second phase the research on the influence of different vertical soil moisture distributions on the signal generation and penetration depth of the sensor will be extended for close to natural conditions to highly-managed systems, mainly for an agricultural land use. To achieve this, CRNS measurement will be evaluated, if existing already, or performed at different field sites impacted by shallow groundwater within the CRNS penetration depth or by dedicated artificial sprinkling irrigation experiments in cropped fields. This large band width of vertical soil moisture distributions will be the basis for a systematic assessment of the CRNS penetration depth where related to agricultural applications.The fundamental understanding of vertically heterogeneous distribution of water within the rooted soil profile and the CRNS variable penetration depth will enable to target a more comprehensive view on water storage and fluxes in the rooted soil zone based on CRNS measurements, e.g. at a field site with controlled groundwater table levels and drainage conditions. With that a larger focus shall be set on CRNS and plant-soil interaction, and thus the roots of vegetation as driving water storage changes, being decisive for replenishment of the deeper subsoil layers after drought and groundwater recharge. Also, they themselves are potentially affected by water stress and creating irrigation demands, and its management can be supported by CRNS-based measurements or modeling. Measurements and simulations of soil moisture profiles and its effect on CRNS penetration depth will not only be essential for this project but also for other projects within the research unit because it is fundamental for estimating the full root zone water fluxes and water balance calculations. Resulting soil moisture profiles will be, for example, integrated into the depth scaling approaches of hydrogeodesy, will support the regionalization efforts and better constrain snow water equivalents measured by CRNS. In addition, we will define synthetic soil moisture data sets for testing CRNS interpretation, radiative transfer models and hydrogravimetry approaches at small catchment scale together with other research modules in one of the Cosmic Sense cross-cutting activities, and will be in charge for its overall organization.