globalchange  > 气候变化事实与影响
DOI: 10.5194/hess-18-5361-2014
Scopus记录号: 2-s2.0-84919481613
论文题名:
What causes cooling water temperature gradients in a forested stream reach?
作者: Garner G; , Malcolm I; A; , Sadler J; P; , Hannah D; M
刊名: Hydrology and Earth System Sciences
ISSN: 10275606
出版年: 2014
卷: 18, 期:12
起始页码: 5361
结束页码: 5376
语种: 英语
Scopus关键词: Aquatic organisms ; Atmospheric temperature ; Budget control ; Catchments ; Cooling ; Cooling systems ; Cooling water ; Digital storage ; Economics ; Groundwater ; Land use ; Sun ; Thermal gradients ; Weather information services ; Automatic weather stations ; Cooling water temperature ; Daily maximum water temperature ; Hemispherical photographs ; Spatiotemporal variability ; Streamwise directions ; Temperature-Sensitive ; Water temperature data ; Rivers ; cooling ; deciduous forest ; energy budget ; energy flux ; heat flux ; photography ; solar radiation ; spatial distribution ; spatiotemporal analysis ; streamwater ; temperature gradient ; water temperature ; weather station ; woodland ; Aberdeenshire ; Girnock Burn ; Scotland ; United Kingdom ; Coniferales
英文摘要: Previous studies have suggested that shading by riparian vegetation may reduce maximum water temperatures and provide refugia for temperature-sensitive aquatic organisms. Longitudinal cooling gradients have been observed during the daytime for stream reaches shaded by coniferous trees downstream of clear cuts or deciduous woodland downstream of open moorland. However, little is known about the energy exchange processes that drive such gradients, especially in semi-natural woodland contexts without confounding cool groundwater inflows. To address this gap, this study quantified and modelled variability in stream temperature and heat fluxes along an upland reach of the Girnock Burn (a tributary of the Aberdeenshire Dee, Scotland) where riparian land use transitions from open moorland to semi-natural, predominantly deciduous woodland. Observations were made along a 1050 m reach using a spatially distributed network of 10 water temperature data loggers, 3 automatic weather stations and 211 hemispherical photographs that were used to estimate incoming solar radiation. These data parameterised a high-resolution energy flux model incorporating flow routing, which predicted spatio-temporal variability in stream temperature. Variability in stream temperature was controlled largely by energy fluxes at the water-column-atmosphere interface. Net energy gains occurred along the reach, predominantly during daylight hours, and heat exchange across the bed-water-column interface accounted for <1% of the net energy budget. For periods when daytime net radiation gains were high (under clear skies), differences between water temperature observations increased in the streamwise direction; a maximum instantaneous difference of 2.5 °C was observed between the upstream reach boundary and 1050 m downstream. Furthermore, daily maximum water temperature at 1050 m downstream was g‰Currency sign1 °C cooler than at the upstream reach boundary and lagged by >1 h. Temperature gradients were not generated by cooling of stream water but rather by a combination of reduced rates of heating in the woodland reach and advection of cooler (overnight and early morning) water from the upstream moorland catchment. Longitudinal thermal gradients were indistinct at night and on days when net radiation gains were low (under overcast skies), thus when changes in net energy gains or losses did not vary significantly in space and time, and heat advected into the reach was reasonably consistent. The findings of the study and the modelling approach employed are useful tools for assessing optimal planting strategies for mitigating against ecologically damaging stream temperature maxima. © 2014 Author(s).
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/78028
Appears in Collections:气候变化事实与影响

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作者单位: School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom; Marine Scotland Science, Freshwater Laboratory, Faskally, Pitlochry, Perthshire, United Kingdom

Recommended Citation:
Garner G,, Malcolm I,A,et al. What causes cooling water temperature gradients in a forested stream reach?[J]. Hydrology and Earth System Sciences,2014-01-01,18(12)
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