The chemistry, mineralogy, and rates of transport of sediments in the ...

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greater range of bottom sediment particle sizes, compared to rivers of
high b values . Rivers and streams having high values of b were observed
to have highly scoured, large particle-sized beds with shifting, unstable,
and highly mobile bedload movements, which usually are unfavorable substrates
for aquatic organisms . Rivers and streams with lower values of b
tend to have a wider range of sediment particle sizes, a more stable sediment
surface, and apparently low bedload transport rates (see for . example
the discussion on bedload transport of Jean Marie River below) .
Our selection of watersheds and sampling sites (largely controlled
by the . location of Water Survey of Canada discharge stations) has biased
the Mackenzie Valley data somewhat by representing only 3 types of watersheds
: a) Group 1 large rivers draining from the mountains, high b and
low a, b) Group 2 moderate to small rivers and streams draining the Mackenzie
Valley lowlands, low b and high a,-and c) Groups 3 rivers draining large
lakes or large numbers of lakes, to which the above interpretation of
slopes and intercepts probably does nr -apply . From our rough survey data
(see Brunskill et aZ . 1973, vol . 2, and Campbell et aZ . 1975) and topographic,
climatic, terrain and vegetation maps, we feel that there are
several types of watersheds not represented in Table 1 and Fig . 1 . For
example, small mountain streams, and large rivers draining spruce-muskeg,
low relief watersheds, are watershed types that probably would require
new categories . Twisty Creek, a small (Ad - 6 .94 km 2 ) mountain headwater
stream (Q a 1 .1 - 2 .3 x 10 6 m 3yr- 1) in the Arctic Red River watershed,
has a slope (b) of 2 .18, an intercept (a) of 94 .8, and an SSW of 81 to 659
metric tons km-2yr-1 (Jasper, 1974) . . This small stream is clearly of a
different character from those listed in Table 1, 2, and 3 and Fig . 1, and
represents a category of small streams that have highly erodible watersheds
and a great capacity to carry sediment . Twisty Creek values of b
and annual suspended sediment erosion rate (SS W ) fit nicely on the
previously mentioned regression line for these same parameters for watersheds
in Table 1 . However, Twisty Creek carries nearly 50% of its total
sediment load as bedload .
As indicated by MUller and Forstner (1968), the above discussion could
be repeated considering stream velocity (V) instead of discharge (i .e .
SSi a aV') . This would probably result in similar trends, but we have not
studied this relationship thoroughly . The great disadvantage of the use of
Qi - SS, curves to consider the effects of sediment addition on streams is
that the technique does not allow extrapolation to other, unsampled watersheds .
However, careful measurement, of Qi and SSi on calibration, control, naturally
and technologically_disturbed watersheds will essentially test the hypotheses
suggested above, and provide examples for use in consideration of development
in other similar watersheds .
Most of the above discussion on the relationships between Qi and SS4,
probably also applies to nutrient elements in particulate form (Tables 11
and 12, Figs . 3 and 4), and to most major and minor elements in particulate
form (?Ca, PCu, PZn, PSi, PA1), since these elements appear to form a
relatively- constant proporation of SSi in the sampled rivers (Table 14) .