4.1 Stream discharge
At the onset of snowmelt, in late May 2019, discharge increased rapidly
by an order of magnitude (Figure 3C). Streamflows were high from June 4
to July 8, after which levels receded. There were several peaks in
discharge corresponding to air temperature fluctuations (Figure 3B).
Discharge from GS2 and GS3 were combined to represent the combined
outflow from W2 and W3. Maxima of 0.24, 0.63 and 0.55
m3 s-1 were attained at GS1, GS2 +
GS3 and GS4, respectively. Discharge typically increased by 10 % to 30
% between GS1 and GS2, however during snowmelt this went up to 80 %.
Diurnal discharge fluctuations, that became more pronounced downstream,
were likely caused by evapotranspiration because daily discharge minima
occurred between 14:00 and 15:00 and maxima occurred before sunrise.
Three spring temperature and location surveys were carried out during
the 2019 field season (Figure 4). On June 26, 25 discrete springs were
identified. By August 7, the number of springs was reduced to 16 and by
September 26 to seven. Not only did the number of springs decrease over
the season but the springs also moved northward to lower elevations,
corresponding with a decline in the water table. The highest elevation
spring was at 2086.3 m.a.s.l. on June 16 and at 2083.7 m.a.s.l. on
September 26.
Spring temperatures on June 26 ranged from 1.1 to 3.6 °C. On August 7,
temperatures increased to 2.1–7°C and on September 26 they decreased to
1.9–3.4°C (Figure 4). The warmest springs were initially concentrated
in the south-eastern part of the spring system but moved to the eastern
stream bank over the course of the season. On September 26, the warmest
spring was also the furthest north. Each of the three snapshots in
Figure 4 corresponds to different phases in Hathataga Lake’s
hydroperiod. In (A) the lake water level (WL) was near its peak (2090.0
m.a.s.l., WL = 1.5 m), in (B) the lake temperature was near its peak
(2088.8 m.a.s.l., WL = 0.35 m), and in (C) the lake had dried up (2087.8
m.a.s.l., WL = -0.68 m). Note that WL is the water level with reference
to the lakebed.