Figure 33. Hydrostation record at Spring Gully.
Salinity remains more uniform at the remaining
sites--Bread Truck, B and Otter gullies--and this
Hydrostation data from the Otter Creek site
uniformity reflects the continuous flow of water
appear to confirm our 1993 hypothesis that the
out of the respective pond sources, each of which
dominant source water for this area is both Eagle
has ground water influx from springs. In general,
River and the upland springs that feed Otter
the peak turbidity levels, which are consistent
Creek, which enters ERF from the west. Salinity
with those of Knik Arm, increased during flood-
remained very low throughout the summer, in-
ing events through the season (e.g., Fig. 34).
dicative of the freshwater discharge from the up-
lands southwest of Area B (Fig. 35).
During tides without floods, water tem-
peratures drop semi-diurnally to levels
similar to those recorded in Eagle River
(Table 11). This behavior shows that
when high tide levels are low, Knik Arm
waters lack momentum and time to pen-
system (i.e., Area B); however, back-
pressure from inflowing tidal water ap-
pears to dam the Eagle River and divert
it into Otter Creek and the southwest-
ern reaches of the Flats (Fig 35a). Dur-
ing the extremely high tides of late fall,
Knik Arm waters did have enough en-
ergy and elevation to penetrate deep
into this area, as indicated by the salin-
ity increases in Otter Creek at that time
(Fig. 24). The salinity increase at Otter
Creek during the November floods is
longer and more pronounced (Fig. 35c).
The snow cover on the Flats at that time
retarded the runoff during ebb because
of its capacity to store flood water. Its
slow release probably was the primary
cause of the longer period of high sa-
Figure 34. OBS levels at Parachute Gully during flooding periods
snow is much slower than normal ebb
in June, September, October and November 1994.
runoff without snow.