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researchers in Australia, who identified cold groundwater
inputs that were ostensibly important for the survival of
rainbow trout (
Oncorhynchus mykiss
) in theMurray River
(Hick and Carlton, 1991). The TIR images, collected from
a fixed-wing aircraft mounted with a multispectral scan-
ner, were particularly effective in the brackish sections
of the Murray River where cool groundwater rose to the
surface because it was less dense than saltwater. Subse-
quent work - like that in the Murray River - focused on
thermal anomalies associated with wall-based channels,
groundwater inputs, and thermal refugia important for
salmon in the Pacific Northwest (USA) (Belknap and
Naiman, 1998; Torgersen et al., 1999). The impetus for
suchwork arose fromthe need to identify localisedpatches
of cool water (e.g., Figure 5.1), but the utility of these
data became even more apparent for assessing thermal
diversity at broader spatial scales in the floodplain (e.g.,
Figures 5.2, 5.3, and 5.11) and longitudinally over tens
of kilometers (Figure 5.4). Direct applications in fisheries
continue to be conducted (Madej et al., 2006), but by far
the most extensive use of TIR remote sensing has been
by natural resource management agencies seeking to cali-
brate spatially explicit river temperature models for entire
watersheds (Figure 5.4; Boyd and Kasper, 2003; Oregon
Department of Environmental Quality, 2006). Prior to
the availability of near-continuously sampled longitudi-
nal water temperature data derived from airborne TIR
remote sensing, discontinuities associated with ground-
water inputs and hyporheic flow were very difficult to
quantify empirically.
5.2 State of the art: TIR remote sensing
of streams and rivers
The remote sensing of surface water temperature using
measurements of emitted TIR radiation (3-14
m) can
provide spatially distributed values of T
r
in the 'skin'
layer of the water (top 100
μ
m). This is a well-established
practice (Mertes et al., 2004), particularly in oceanog-
raphy where daily observations of regional and global
sea-surface temperature (SST) are made from satellites
(Anding and Kauth, 1970; Emery and Yu, 1997; Kilpatrick
et al., 2001; Parkinson, 2003). In the terrestrial environ-
ment, TIR remote sensing of surface water temperature
initially focused on lakes (LeDrew and Franklin, 1985;
Bolgrien and Brooks, 1992) and coastal applications such
as thermal pollution from cooling water discharge from a
nuclear power plant (Chen et al., 2003), but starting in the
1990s airborne TIR remote sensing has been conducted
by government agencies over thousands of kilometers of
rivers to monitor water quality, identify sources of cold-
water inputs, and to develop spatially referenced river
temperature models (Faux and McIntosh, 2000; Faux
et al., 2001; Torgersen et al., 2001).
Applications of TIR technology to measure water tem-
perature of rivers are diverse and have been employed in a
wide variety of fluvial environments. Published examples
of thermal maps can be found in the early 1970s (Atwell
et al., 1971), and one of the earliest documented uses of
TIR imaging to evaluate fish habitat in a river was by
μ
Coldwater
seep
25 m
Figure 5.1
Natural-color (a) and airborne
TIR (b) aerial images of cold-water seepage
area in the Crooked River (Oregon, USA) in a
high-desert basalt canyon (27 August 2002).
The colored portion of the TIR temperature
scale spans the approximate range in water
surface temperature in the image; land and
vegetation surface temperature are depicted
in shades of gray. Lateral cold-water seeps,
such as the one depicted above, are relatively
small in area but provide important thermal
refugia for coldwater fishes. (United States
Bureau of Land Management, Dept. of
Interior, USA; Watershed Sciences, Inc.,
Corvallis, Oregon, USA).
(a)
(b)
Warm
Cool
13
°
C
17
°
C
20
°
C
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