Collaborative Research: Mapping Changes in the Active Stream Channel Network in Mesoscale Watersheds in order to Understand Distinct Signatures in Event Recession Curves

流域中的水流最常通过测量流域出口处的水流或通过在流域内的威尔斯中进行点测量来研究。两者都不足以获得流域功能的全貌，因为出口处的测量可能过于广泛，而点测量过于局部化。该项目旨在通过绘制整个流域活跃河道的扩张和收缩图，并深入了解流域的哪些区域对流域出口有贡献或没有贡献，从而填补知识空白。这将提供新的知识，更好地了解水，土壤和化学品如何通过流域移动，以及河流流量将如何变化，特别是在降水量很少的时期。作为该项目的教育和推广工作，该项目将为初中和高中理科学生提供实践学习机会，并帮助培训研究生。在水文科学中，长期以来一直使用降雨结束后观测到的溪流流量下降率（即退流）和同期溪流流量值来推断流域尺度的含水层特性。 然而，新的工作表明，在整个流域的溪流源区的空间变化可以解释衰退以及或更好地比含水层的属性和水力学。因此，关于什么才是真正控制经济衰退的因素的辩论正在兴起。解决这一争论可以提供流域功能的基本见解。为了调查经济衰退的控制措施，该项目将在美国不同地点的多达六个中型流域安装高密度传感器网络，以绘制活跃河道网络范围的变化。传感器测量的流量将补充与视觉映射的活动流网络，热成像可能的地下水输入流，土壤湿度测量。该项目可能对预测无资料流域的流量和了解溶质在流域中移动的过程产生更广泛的影响。

Water flow in watersheds is most often studied by either measuring stream flow at the watershed outlet or by making point measurements in wells within the watershed. Neither is adequate for gaining a complete picture of watershed function because measurements at the outlet can be too broad and point measurements too localized. This project seeks to fill the knowledge gap by mapping the expansion and contraction of active stream channels throughout the watershed and providing insights into which areas of a watershed are or are not contributing flow to the watershed outlet. This will provide new knowledge for better understanding how water, soil, and chemicals move through watersheds and how stream discharge will change, particularly during periods of little precipitation. As an education and outreach effort of this project, the project will develop hands-on learning opportunities for middle and high school science students and help train graduate students. Pairs of observed rates of stream flow decline after rainfall ends (i.e. recession flow) and the concurrent stream flow value have long been used in the hydrologic sciences to infer aquifer properties at the watershed scale. However, new work has shown that spatial variation in stream flow source areas across a catchment may explain recession as well or better than aquifer property and hydraulics. Thus, there is an emerging debate on what really controls recession. Resolving this debate can provide fundamental insights into watershed function. To investigate the controls on recession, this project will install high-density sensor networks at up to six medium-sized watersheds at different locations throughout the U.S. to map changes in the extent of the active stream channel network. Sensor measurements of discharge will be supplemented with visual mapping of the active stream network, thermal imaging of likely groundwater inputs to streams, and soil moisture measurements. The project could have broader implications for predicting discharge in ungauged basins and understanding processes of solutes moving through watersheds.