Headwater Stream Processes Revealed by Continuous Ultra-high Resolution Thermal Measurement

在了解源头集水水文学方面的进展是有限的。目前几乎所有的测量技术都是基于点的。这对于溪流的研究尤其有问题，因为水流和水流成分的测量是在测量站进行的--但感兴趣的过程是沿河道纵向分布的。该项目建议在利用流内温度、多个微型气象站和水文示踪器的超高分辨率测量所测量的热量和溶质传输的基础上，探索源头流过程。我们的初步研究表明，这些新技术可以改变对溪流水文和溪流热通量的理解，揭示不均匀的地下水流入、地下水交换和小气候条件。我们将使用多参数数据测井探头观测溪流中温度、溶解氧、比电导率和pH的自然变化和外加(热和溶质示踪剂)变化，并使用光纤分布式测量系统(DTS)以每米每小时0.03oC的精度测量溪流温度。20个自主气象站将在无线网络中监测河流沿线的9个变量。这些研究将在HJ Andrews实验森林和LTER地点进行，在过去20年里，那里的溪流温度研究一直是一个重点。类似设计的平行实验将在卢森堡的Maisbich与TU Delft和EPFL合作进行，那里的气流温度研究正在进行中。在现有正演模式的基础上，发展了一个可逆的水温和溶质运移数值模式。这将允许估计整个河流长度上的地表和地下水流系统的物理特征，分辨率达到米级，测试河流过程的概念化。长期以来，水文科学一直被迫使用少数几个点测量(例如，流量计、热电偶、雨量计)来描述不同类型的水文系统。DTS/数据探头/网络传感器相结合的方法在时间上连续提供超过1000个测量点，这是一个史无前例的数据集，有助于重新检查跨越三个数量级的溪流-山坡相互作用，并测试基于过程的流函数概念化。由于热能是守恒的，热将被用作示踪剂，通过观察自然信号和施加的信号来实现。数百个地点的同时示踪剂探测为探索水文过程提供了无与伦比的广泛适用的工具。拟议的研究将发展和利用这一方法，扩大我们对水源系统的了解，并为社会提供一系列工具来进行进一步的研究。该团队是唯一有资格进行这项研究的团队，包括山坡/溪流过程(Selker，McDonnell)、溪流温度(Johnson)和水文仪器(Selker)的领导者。布罗德影响这个项目有三个主要任务：(1)阐明生态关键的溪流过程；(2)发展广泛有用的研究方法；以及(3)培训研究生和本科生(9名直接由所需资金资助)。方法方面的发展包括：将DTS应用于水系；开发一个可逆的数值模型来解释联合DTS和地球化学数据；以及开发和测试热热脉冲系统。每一种都是新颖的，在理解源头溪流的水文学和生态方面都有广泛的用处。过程将在迄今未被观测到的规模上进行研究，这将揭示对生态功能至关重要的地下水/地表水相互作用的规模和程度。这一认识对于更有效地保护由于夏季消费需求高峰期溪水温度较高而濒临灭绝的许多物种至关重要。除了来自HJ Andrews REU和野外夏令营项目的现场学生外，还将资助六名本科生参与该项目，为他们提供培训并激励他们继续进行研究和教育。两名硕士生和博士生将有机会开展批判性研究，并参加国家科学会议。这位博士生还将参加一项国际合作，为合作的国际探索职业生涯打开大门。

Progress in understanding headwater catchment hydrology is measurement limited. Almost all current measurement techniques are point-based. This is especially problematic for the study of streams, where measurements of flow and components of flow are made at a gauging station--but the processes of interest are distributed longitudinally down the channel. This project proposes exploration of headwater stream processes based on heat and solute transport measured using ultrahigh resolution measurements of in-stream temperatures, multiple micrometeorological stations and hydrologic tracers. Our preliminary research has shown that these new technologies can transform understanding of stream hydrology and stream heat fluxes, revealing heterogeneous groundwater inflows, hyporheic exchange, and microclimatic conditions. We will observe both natural and imposed (heat and solute tracers) variations in temperature, dissolved oxygen, specific conductivity and pH in the stream using multi-parameter data logging sondes, and use a fiber optic Distributed Measurement Systems (DTS) to measure stream temperatures with 0.03oC precision every meter, every hour. 20 autonomous climatic stations will monitor nine variables along the stream in a wireless network. These studies will take place at the HJ Andrews Experimental Forest and LTER site, where stream temperature research has been a focus for the past 20 years. A parallel experiment of the similar design will take place in the Maisbich, Luxembourg in collaboration with TU Delft and the EPFL, where stream temperature studies are ongoing. An invertible numerical model of stream temperature and solute transport will be developed based on the currently operational forward model. This will allow estimation of physical characteristics of the surface and subsurface flow system along the entire length of the stream with resolution to the meter level, testing conceptualization of stream processes.Intellectual MeritHydrologic science has long been forced into the characterization of heterogeneous hydrologic systems using a handful of point measurements (e.g. stream gauges, thermocouples, rain gauges). The combined DTS/data-sonde/networked sensor approach provides over 1000 points of measurement continuously in time, an unprecedented data set, facilitating reexamination of stream-hillslope interactions across three orders of magnitude in scale and testing of process-based conceptualizations of stream function. Since thermal energy is conserved, heat will be used as a tracer, both through observation of natural and imposed signals. The simultaneous tracer detection at hundreds of locations provides an unparalleled broadly-applicable tool for exploring hydrologic processes. The proposed study will both develop and make use of this methodology, expanding our understanding of headwater stream systems, and the range of tools available to the community to carry out further studies. The team is uniquely well qualified to carry out this study, including leaders in hillslope/stream processes (Selker, McDonnell), stream temperature (Johnson), and hydrologic instrumentation (Selker).Broader ImpactThis project has three major thrusts: (1) elucidation of ecologically critical stream processes; (2) development of broadly useful research methodologies; and (3) training of graduate and undergraduate students (nine directly supported by the requested funds). Methodological developments include: application of DTS to stream systems; development of an invertible numerical model to interpret joint DTS and geochemical data; and the development and testing of a thermal heat pulse system. Each is novel and widely useful in understanding the hydrology and ecology of headwater streams. Processes will be studied at scales heretofore unobserved, which will reveal the scales and extents of groundwater/surface water interactions critical to ecological function. This understanding is essential to more effectively protect the many species endangered due to high temperatures of stream waters in summer months during peak consumptive demand. Six undergraduates will be funded to work on the project, in addition to the on-site students from the HJ Andrews REU and field camp programs, giving them both training and incentive to pursue further research and education. The two master's students and the PhD student will be given the opportunity to carry out critical research, as well as taking part in national scientific meetings. The PhD student will also take part in an international collaboration, opening doors for a career of collaborative international exploration.