Heat Budget in the Hyporheic Zone of a Large, Gravel-Bed River

该项目是一项基于定量物理的大河潜流带热量收支研究。这与当前关于水温和潜水通量相互作用的研究是相关的。了解潜流带中的热传递对美国西部的水质及其调节具有重要意义，并可能为研究人员、监管人员和水处理专业人员提供一种新的工具。初步结果表明，温暖的河水在通过砾石坝的过程中经历了潜水冷却。围绕着潜水冷却战略，正在设计河流恢复和污染信贷交易计划，这使得对这一现象的充分理解成为当务之急。最初的假设包括：(1)温暖的白天水在低渗流区实际上并没有被冷却，但在白天确实排出了凉爽的夜间水，(2)温暖的白天水被显著冷却，a)热流通过传导到具有较长流动路径的更深的地下水并与其混合，b)潜热和感热通量到包气带，和/或c)在低渗流带的砾石和死区中的临时储热。这些假说的初步测试将通过现场仪器和对俄勒冈州威拉米特河上一条砾石河床上砾石坝下的水和热通量的模拟来完成。该研究地点代表了一种最近沉积的砾石坝，其类型被发现可提供显著的明显降温。来自现场测绘、浅井、地震剖面和示踪剂测试的现场数据将描述和促进底物及其相关通量的建模。这种描述和建模将限制以下后续研究的范围和方法：(1)井的平台布局是否足以测量横向平流热通量，(2)是否需要更多的井来测量更深的热通量和储存，(3)是否需要三维地震数据采集和/或全面层析分析和波形建模，以确定边界条件。

This project is a quantitative physics-based study of the heat budget in the hyporheic zone of a large river. It is relevant to current research in the interactions between stream temperature and hyporheic water flux. Understanding heat transfer in hyporheic zones has important implications for water quality and its regulation in the western US, and may be a new tool for researchers, regulators, and water treatment professionals. Preliminary results indicate that warm river water undergoes hyporheic cooling during its transit beneath gravel bars. River-restoration and pollution-credit-trading schemes are being designed around hyporheic cooling strategies, and this makes a full understanding of this phenomenon an imperative. Initial hypotheses include: (1) warm, daytime water is not actually cooled in the hyporheic zone but does push out cool, nighttime water during the day, (2) warm, daytime water is significantly cooled by a) heat flow by conduction to and mixing with deeper groundwater with longer flow paths, b) heat flow by latent and sensible heat fluxes to the vadose zone, and/or c) temporary heat storage in gravels and dead zones in the hyporheic zone. Preliminary tests of these hypotheses will be accomplished through field instrumentation and modeling of water and heat fluxes beneath a gravel bar on a large, gravel-bed river, the Willamette River, Oregon. The research site represents a recently deposited gravel bar of the type found to provide significant apparent cooling. Field data from, site surveying and mapping, shallow wells, seismic profiles, and tracer tests, will characterize and facilitate modeling of the substrate and associated fluxes. This characterization and modeling will constrain the scope and methods for a follow-up study of (1) the adequacy of the platform layout of wells to measure laterally advective heat fluxes, (2) the need for additional wells to measure deeper heat fluxes and storage, (3) the need for three-dimensional seismic data acquisition and/or full tomographic analysis and waveform modeling, to determine boundary conditions.