habitat, provided the amount of leaves added to
not deteriorate while the leaves are covered by
the river by dusting does not exceed the aerobic
snow, the presence of the leaves melts the overly-
capacity of the river (i.e., the decaying leaves use
ing snow sooner. Thus, the ice surface will be
all of the dissolved oxygen in the river).
exposed to solar radiation, thereby hastening ice
Minshall et al. (1983) indicate that the leaf con-
decay.
centration that falls into Northeastern rivers of the
The conditions under which this evaluation was
size like the Winooski and White is around 100 to
performed were less than ideal. There were only
200 g/m2. The estimated leaf coverages from these
seven days of cloudless weather during the 21-day
dusting tests on the Winooski and White Rivers
evaluation at Montpelier and five cloudless days
were 60 and 190 g/m2, respectively. Thus, the
during the 13 days at Hartford. Nevertheless, at
amount of leaves spread on the ice in both Mont-
Montpelier we observed the snow deteriorated
pelier and Hartford is about the same as what falls
faster in the test section over the 16-day period
naturally on the river in the fall, effectively dou-
from 9 March to 25 March. We saw similar results
bling the annual amount of leaves going into the
at the test sites in Hartford. Additionally, at the
treated reach. This increased leaf loading is ex-
one Hartford site we saw a noticeable decrease in
pected to affect the acidity and turbidity of the
the ice cover thickness in the test section of about
water as well as affect the level of dissolved solids
0.30.4 cm per day as compared to the control.
and fine particles in the water. To what degree this
Since this is a modest amount of ice loss we hesi-
impacts the riverine habitat requires further study.
tate to say that the leaves were effective in
melting the ice cover, since variability in the
river hydraulics throughout the test reach could
Discussion of field test results
From the tests both at Montpelier and White
confound these results. Nevertheless, the trend
River we demonstrated the effectiveness of spread-
shows promise, and requires further work to con-
ing leaves on the ice using a hydroseeder. We
firm the effectiveness of leaves for melting an ice
found that considerable amount of area can be
cover.
covered in a short time using this method. Taking
We cannot say that we promoted premature re-
into consideration time for refilling the seeder 's
lease of the ice due to our efforts. Nonetheless, it
tank and travel time from the filling station to the
is clear that the leaf mulch was effective in reduc-
river, 6.4 hectares could be covered per day using
ing the thickness of ice in the Bridge Street test
this method. At this rate of application we esti-
area, which would result in weaker ice in that area
mate the cost per dusted hectare to be about 6.
than otherwise would have existing naturally.
This compares favorably with dusting using air-
craft, which we estimate could cost 4/ha. Ac-
cessibility to the river is necessary for using a
CONCLUSIONS AND RECOMMENDATIONS
hydroseeder. A location where a road runs paral-
lel to the river is ideal for using a hydroseeder.
From the tests conducted on the ice-covered
Even with the 120-m hose that is available for the
pond, we found that dusting can reduce the al-
hydroseeder, there needs to be good access to the
bedo of the snow and ice from 0.50.9 to 0.10.2.
river if the hydroseeder is to be used for dusting.
This reduction in surface albedo was shown to ac-
Rates of coverage using the hydroseeder are cut
celerate the melting of the snow cover and the thin-
in half if the hose is used instead of the cannon.
ning of the ice cover on the pond. Of the materials
Consequently we could expect the cost per hect-
tested we found sand, coal dust and leaves were
are using the hose to be around
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,100.
the most effective at reducing the albedo of snow
The leaves proved to be effective for melting
and ice surfaces. We found that the leaves and sand
snow even when covered by up to 33 cm of snow.
were about equal in their ability to accelerate the
It may be effective for snow depths greater than
melting of snow and ice. The leaves naturally oc-
this, but that was the deepest snow we observed
cur in New England rivers and are biodegradable;
during our test period. From Dozier et al. (1989)
thus, used in moderate amounts, they should not
we find that incident solar radiation can penetrate
adversely affect the stream habitat.
snow depths of 10 to 20 cm, but the fraction of
From the field trial conducted on two Vermont
transmitted radiation decreases exponentially with
rivers we found the leaves were effective at melt-
snow depth. Thus, we expect that snow depths
ing the snow cover, even when covered with up
much greater than 18 cm may block any radiation
to 13 cm of snow. It is less clear how effective the
from reaching the leaves. Even though the ice may
leaves were at melting the ice cover, although the
14
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