Thermal Infrared Remote Sensing of Water Temperature in Riverine Landscapes - Fluvial Remote Sensing for Science and Management - page 87

20 m

(a)

Subsurface
flow

Springs

(b)

Cool

Warm

15 ° C 20 ° C 25 ° C

Figure 5.2 Natural-color (a) and airborne TIR (b) aerial images of groundwater springs flowing into the upper Middle Fork John
Day River (Oregon, USA) in a montane meadow (16 August 2003). See Figure 5.1 for clarification of color and grayscale thermal
classification. Complex subsurface hydrologic flow paths and areas of increased soil moisture adjacent to the wetted channel are
revealed by lower TIR land and vegetation radiant temperature (United States Bureau of Reclamation, Dept. of Interior, USA;
Watershed Sciences, Inc., Corvallis, Oregon, USA).

In the last decade, the increased awareness of TIR
technology, combined with technological advances that
have made TIR imaging systems more stable, portable,
and affordable, has led to novel applications in riverine
ecology. Both airborne- and ground-based approaches
have proven highly effective for identifying and mapping
the extent of very-fine resolution thermal heterogeneity
associated with point sources, hyporheic flow, discharge
patterns, and geothermal inputs within the river channel
(Burkholder et al., 2008; Cardenas et al., 2008; Dunckel
et al., 2009; Cardenas et al., in press). Other studies have
utilised the entire swath width of TIR imaging systems
to assess thermal variation beyond the river channel and
across the floodplain and adjacent riparian areas (Rayne

andHenderson, 2004; Arrigoni et al., 2008; Smikrud et al.,
2008; Cristea and Burges, 2009; Tonolla et al., 2010).
Recent developments in TIR remote sensing of rivers
have expanded the area of interest beyond water sur-
face temperature - but there is much to be learned from
viewing the entire 'thermal landscape' of rivers, laterally,
longitudinally, vertically, and temporally. The vertical
and temporal dimensions of thermal diversity in river-
ine systems have just begun to be investigated with TIR
remote sensing. The vertical dimension, or thermal strat-
ification, is poorly understood in TIR remote sensing
because measurements of radiant temperature are made
only in the surface layer of the water (approximately top
10 cm), which may not be representative of T k further
down the water column (this will be expanded on in a