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

该项目通过应用地理技术和概念，研究了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英里）被指定为水质有限；这些河流中的大多数（81%）被列入名单，因为夏季最高气温超过了维持历史上冷水渔业的标准。该项目将阐明哪些因素控制着河流网络中所有位置的河流温度模式。将考虑四个主要因素：(1)植被和地形的遮阳；(2)邻近地形或深层地下水源的感热和地下水通量；(3)与潜流带的水流交换；(4)上游河段的输入。利用现有的GIS层和空间分布的河流、空气和土壤温度和排放的实地测量，将开发和测试关于控制河流温度模式的因素的空间明确假设。在俄勒冈州喀斯喀特西部62平方公里的森林盆地中，将研究50到100个地点。从这一分析中得出的推论将与选定的热平衡计算和空间统计分析相证实，以消除虚假的相关性。研究结果将总结在示意图中，描绘了对流温度控制的类型、大小和空间安排。该项目将产生一种通用的、可转移的方法，以理解地上和地下景观属性（即植被和地形与地貌特征）的空间安排如何控制排水网络中河流温度的模式。这种方法与开发基于过程的景观网络功能概念模型的科学目标相关，也与制定联邦和州授权的水质管理计划的社会需求相关，以纠正由极端溪流温度引起的水质违规。现行法律要求“温度限制”河流沿岸的土地所有者制定降低河流温度的计划；导致河流温度升高的因素的不确定性可能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，这项研究的结果将证明，不同地点的不同类型的河流如何或多或少地容易受到植被移除或其他土地利用变化引起的温度升高的影响。该项目还有望证明土地利用的改变是否有助于降低不同地区的河流温度。

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.