2.2 Raft and Shore Flux Tower
Figure 3 shows the two flux towers that were deployed on the research
site: a 3 × 3-m raft (measurement height of 2.0 m) deployed from June to
October each year and a permanent shore tower (measurement height
fluctuating between 11 and 28 m depending on the water level) (Fournier
et al., 2021; Pierre et al., 2022). At both sites, the eddy covariance
technique was used to calculate turbulent heat fluxes from raw 10-Hz
turbulence data.
The raft was anchored between two islands to offer protection against
large waves, in a 30-m deep section of the reservoir. The raft hosted a
fast-response sonic anemometer coupled with an infrared gas analyzer
(IRGASON, Campbell Scientific, USA), a net radiometer (Kipp & Zonen,
The Netherlands) and a temperature probe, all mounted 2 m above the
water surface. Turbulence sensors were oriented eastward to capture the
prevailing wind directions while minimizing flow distortion by the mast.
The raft slowly oscillated along its three Euler angle axis due to
wave-induced motions. To decontaminate raw wind measurements, an
accelerometer (AHRS, Lord Sensing MicroStrain, USA) was attached
adjacent to the anemometer to record pitch, yaw, and roll angles at a
frequency of 10 Hz.
At the shore site, the flux tower was equipped with a combined sonic
anemometer and infrared gas analyzer (IRGASON, Campbell Scientific,
USA), installed 11 m above the maximum water level and pointing toward
the reservoir in the NNW direction. A complete meteorological setup was
also deployed: a TB4 tipping bucket (Hyquest Solutions, USA) for
rainfall measurement, a propeller anemometer (05103, R.M.Young, USA),
and a four-component net radiometer (CNR4, Kipp & Zonen, The
Netherlands). The last two instruments were installed at heights of 10.3
m and 12.3 m, respectively. The radiometer measured all terms of the
radiation budget, namely incoming and outgoing shortwave and longwave
radiation, but since the instrument was installed on the shore, it did
not report the radiation emitted/reflected by the reservoir.