A Spatially-Distributed GIS-Based Analysis of Temperatures in a Stream Network

这个项目通过应用地理技术和概念来研究河流网络中热量的积累、储存和传输。1998年，在俄勒冈州调查的2375条溪流和河流中，有1067条(13892河英里)被指定为水质有限；这些溪流中的大多数(81%)被列入名单，因为夏季最高温度超过了为维持历史悠久的冷水渔业而设定的标准。该项目将阐明哪些因素控制河流网络中所有位置的水流温度模式。将考虑四个主要因素：(1)植被和地形的遮蔽，(2)来自邻近地貌或深层地下水来源的感热和地下水的通量，(3)与潜流带的溪水交换，以及(4)上游河段的输入。我们将利用现有的地理信息系统层和对河流、空气、土壤温度和流量的空间分布的现场测量，开发和测试关于控制河流温度模式的因素的空间上明确的假设。在俄勒冈州西部喀斯喀兹一个62平方公里的森林盆地中，将对50到100个地点进行研究。从这一分析中得出的推论将被选定的热平衡计算和空间统计分析所证实，以消除虚假关联。调查结果将在示意图中总结，这些示意图描述了控制气流温度的类型、大小和空间布置。该项目将产生一种普遍的、可转移的方法，以了解地上和地下景观属性的空间安排(即植被和地形与地貌特征)如何控制排水网络中的溪流温度模式。这种方法与开发景观中网络功能的基于过程的概念模型的科学目标有关，也与制定联邦和州规定的水质管理计划以补救极端溪流温度造成的水质违规行为的社会需要有关。现行法律要求“有温度限制”的溪流沿线的土地所有者制定降低河流温度的计划；围绕导致河流温度升高的因素的不确定性可能会加剧土地所有者之间的社会紧张关系。利用地图和实地测量，这项研究的结果将展示不同位置的不同类型的溪流可能或多或少对植被移除或其他土地利用变化导致的气温上升产生影响。预计该项目还将展示土地使用变化如何有助于降低不同地点的溪流温度。

This project investigates the accumulation, storage, and transport of heat in a stream network by applying geographical techniques and concepts. In 1998, 1067 (13,892 river miles) of the 2375 streams and rivers surveyed in Oregon were designated as having limited water quality; most of these streams (81%) were listed because summer maximum temperatures exceeded the standards set for maintaining the historic cold water fisheries. This project will clarify which factors control stream temperature patterns at all locations in a stream network. Four major factors will be considered: (1) shading by vegetation and topography, (2) fluxes of sensible heat and subsurface water from adjacent landforms or deep groundwater sources, (3) exchange of stream water with the hyporheic zone, and (4) inputs from upstream reaches. Spatially explicit hypotheses about factors controlling patterns of stream temperature will be developed and tested using existing GIS layers and spatially-distributed field measurements of stream, air, and soil temperatures and discharge. Between 50 to 100 locations will be studied in a 62 square-kilometer forested basin in the western Cascades of Oregon. Inferences drawn from this analysis will be corroborated with selected heat balance calculations and spatial statistical analyses to eliminate spurious correlations. Findings will be summarized in schematic diagrams depicting the types, sizes, and spatial arrangements of controls on stream temperature. This project will produce a generalized, transferable approach to understanding how the spatial arrangements of above-ground and below-ground landscape attributes (i.e. vegetation and topography versus geomorphic features) control patterns of stream temperatures in a drainage network. Such an approach is relevant to the scientific goal of developing process-based conceptual models of the function of networks in landscapes, and also to the societal need for approaches to preparing federally- and state-mandated water quality management plans to remediate water quality violations caused by extreme stream temperatures. Current laws require landowners along "temperature-limited" streams to devise plans to reduce stream temperatures; uncertainty surrounding the factors causing elevated stream temperatures may exacerbate social tensions among landowners. Using maps and field measurements, the results of this study will demonstrate how different types of streams in different locations may be more or less susceptible to increased temperature from vegetation removal or other landuse changes. The project also is expected to demonstrate how land use modifications may or may not help reduce stream temperatures in various locations.