Geoscience Reference
In-Depth Information
Table 1 Predictions and observations of seasonal changes in transient storage volume according
to their nature
Sites
Nature of transient
storage
Predictions (late summer
to early spring)
Observations
2
Aquatic plants
3
Aquatic plants
4
Stony bed
a
þ
6
Stony bed
7
Stony bed with moss
9
Stony bed (
þ
hyporheic zone?)
10
Stony bed with moss
þ
11
Deep pools (CaCO
3
bed)
14
Stony bed
¼
25% change,
þ
or
¼
25-50% change,
þþ
or
¼ >
50% change
a
Extensive channel reworking and consequent geomorphological changes during the intervening
winter.
0.8
Fig. 4 Bar chart showing
A
s
/
A
for all sites for both
early spring and summer
0.7
Early Spring
0.6
Summer
0.5
0.4
0.3
0.2
0.1
0
9 0 1 4
23467
Site number
streams with more permanent structures such as moss cover and stones was
generally slightly more variable than anticipated from the on-site observations of
the stream characteristics, with no clear direction of change however.
Figure
5
shows some other interesting seasonal aspects of the system. First,
velocities are higher in the early spring than in the previous summer. This is a direct
consequence of the higher flows (the spring fed water being augmented by snow
melt). We see a consistent increase in velocity (and flow) at virtually all sites and
corresponding changes in the exchange coefficient.
We observe decreases in the exchange coefficient from early spring to late
summer ranging from 35% up to 100%; these would impact the ecosystem with
corresponding increases in the retention time in the transient storage zone.
The increase in retention time would allow greater nutrient cycling in the transient
storage zone over the growing season.
