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

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It will be necessary to quantify these judgements listed above . The
baseline or lower limit of sediment supply from a watershed to a stream can
be measured (Table 3), estimated from map measurements of the components of
Eq . 5, estimated from measurement of QQ and Fig . 2, or more crudely estimated
by techniques such as those of Jansen and Painter (1974), Corbel
(1964), or Howard (1974) based upon data specific to the Mackenzie Valley
and the Northern Yukon . Previous to development, estimates of the increase
in sediment supply, per unit land area disturbed, will have to originate
from careful monitoring of sediment accumulation in the stream bed, stream
Qi, SSi,, and bedload transport over several years at existing terrain disturbance
sites, by Eq . 6,, or by direct experimental disturbance of watersheds
in representative regions of the Mackenzie Valley and the Northern Yukon .
Since the effect of watershed disturbance on sediment yield is likely to
be an - increase in no or 'w by a factor of 2 to 100 (see Table 20 in
Brunskili et al ., 1973), or deposition of sediments on the stream bed, we
predict a general decrease in abundance and/or change in species of the
stream flora and fauna in proportion to the mass of,fine sediments added
to the area of the stream bottom (Rosenberg and Snow, 1975, and unpublished) .
We further predict that most of the watersheds to the east of the Mackenzie
River, due to their relatively small watershed areas, low relief, high percentage
forest cover, low velocity and discharge, relatively high transparency
(low suspended sediments), and biological diversity, will be much more
sensitive to increased sediment supply than would the larger, usually turbid
rivers to the west of the Mackenzie River (see also Brunskill et al ., 1973) .
Small, clear-water rivers with headwaters in the Mackenzie lowlands and
which flow to the Mackenzie River from the west, will also be more sensitive
to sediment addition than adjacent rivers with mountainous headwater areas .
Heavy metal-rich wastes or spills, many petroleum products, pesticides,
and synthetic organic materials will enter Mackenzie watersheds during
development . . Many of these technological products, or . their waste products,
will be sorbed, complexed, chelated, or chemically bound to bottom and suspended
sediments of streams . The natural exchange capacity of suspended
sediments (Table 5) is relatively low, but dissolved organic carbon in river
waters (0 .1-1 Mole C m-3 , Brunskill, unpublished) will likely have a great
capacity to transport these types of substances (Pierce et OZ ., 1974) . Our
knowledge of transport rates and'lature of dissolved and particulate organic
matter in Mackenzie and northern Yukon watersheds is inadequate (Peake et a', .,
1972), and our knowledge of the fluxes of-heavy metals from the watershed is
minimal (Table 14, and see Campbell et al ., 1975) .
Requirements for Future Research
In order to guide technological development in the Mackenzie and
northern Yukon, environmental scientists must contribute to a practical
compromise somewhere between the natural, undisturbed ecosystem and a
greatly altered, usually deleteriously changed ecosystem . In order to
seriously contribute to proposals for such a compromise, it is necessary
to have an understanding of a) the natural state of selected, representative
watersheds, and b) an estimate of the impact of the proposed disturbance on