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

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20 I Speculations on theEffectsofTechnologicalDevelopment onStreams, andRivers Based on past experience and experimental studies (see Radforth, 1973 ; Strang, 1973 ; Mackay, 1970), it is likely that any technological activity (on high ice-content fine-grained soils of the Mackenzie and the Northern Yukon) will cause a disturbance to the thermal balance of the vegetationsoil-permafrost system, and will result in thermal erosion . The magnitude of sediment mass t ransferred . to streams, rivers, and lakes from this thermal erosion will likely be proportional to the area of land disturbed by technological activity . Since watershed area, relief, and forest cover exert a dominant control over sediment transport rates (rates of erosion) (see Table 13) we propose that disturbances to the natural stability of the terrain will increase sediment supply in proportion to percentage of the watershed area disturbed by natural and technological events . The duration of the period of increased sediment sup *y caused by one or several discrete major land disturbances is likely to be -in excess of 5 years, based on experience and observation of natural and technologically-caused thermokarst land movements (Mackay, .1970 ; Zoltai, personal communication ; and personal observations by Brunskill and Snow, 1971-74) . It seems likely that small watersheds (Ad
21 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
Page 1 and 2: Department of the Environment Minis
Page 3 and 4: iii TABLE OF-CONTENTS Page List of
Page 5 and 6: V TABLE 8 . Page Mean annual rates
Page 7 and 8: vii LIST OF FIGURES Page Figure 1 .
Page 9 and 10: ix ABSTRACT Brunskill, G . J ., P .
Page 11 and 12: xi RESUMt Brunskill, G . J ., P . C
Page 13 and 14: 1 INTRODUCTION In regions of northe
Page 15 and 16: 3 Stream and river bottom sediments
Page 17 and 18: Annual rates of transport were obta
Page 19 and 20: 7 The total mass of sediments remov
Page 21 and 22: 9 Only two clay minerals were found
Page 23 and 24: 11 increased sediment concentration
Page 25 and 26: 13 changes in albedo, and the gener
Page 27 and 28: 15 Increases in the concentrations
Page 29 and 30: 17 which is positively related to w
Page 31: 19 and velocity (Fig . 1) . For the
Page 35 and 36: 23 CONCLUSIONS 1 . For selected riv
Page 37 and 38: 25 REFERENCES Abrahams, A . D . and
Page 39 and 40: 27 Corbel, J . 1964 . L erosion ter
Page 41 and 42: 29 Hughes, 0 . L ., J . J . Veillet
Page 43 and 44: 33 McRoberts, E . C . and N . R . M
Page 45 and 46: 33 Tarnocai, C . 1973 . Soils of th
Page 47 and 48: , 35 e TABLE 2a . Slopes ') and int
Page 49 and 50: 37 i TABLE 2c . Slopes (b) and inte
Page 51 and 52: i 39 b TABLE 3 . Average annual mas
Page 53 and 54: 41 v b TABLE 5 . Cation exchange ca
Page 55 and 56: N c . P TABLE 7a . Ranges of concen
Page 57 and 58: I a m r TABLE 8 . Mean annual rates
Page 59 and 60: 01 TABLE 10. Mean annual rates of t
Page 61 and 62: 49 TABLE 12 . Significance of regre
Page 63 and 64: TABLE 14 . Mean concentrations of s
Page 65 and 66: 9 Q TABLE 16 . A comparison of annu
Page 67 and 68: TABLE 17 . cont'd River Year Date S
Page 69 and 70: S TAME 17 . cont'd River Year Date
Page 71 and 72: TABLE 17 . cont'd River Year Date Q
Page 73 and 74: It • TABLE 17 . cont'd River Year
Page 75 and 76: TABLE 17 . cant 'd River Year Date
Page 77 and 78: 2 =0.67 100,000- N E Y a 10,000- Y
Page 79 and 80: c 11 I C- 10 - E n I, 0 10- E e 0.1
Page 81: II (m 3 vnnr - ' v In'6 1 r r, m A

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