the east, and immediately north of the junction is the Town
of Dawson, the territorial capital.

From Dawson northwest to a point beyond the
national Boundary, the Yukon is confined to a single broad
channel broken only by occasional islands. In this stretch
it is fed by a number of small tributaries, of which Forty-
mile River is the most important. The International
Boundary between Yukon Territory and Alaska is crossed
about 88 miles from Dawson. About 321 miles below
Dawson the Yukon is joined by the Porcupine at Fort
Yukon, and 308 miles westward Tanana
the Yukon at Tanana. From Tan
downstream to the delt

Inter-

River merges with
ana, Navigation is possible

a, and also up Tanana River to

Nenana where connection may be made with the Al
Railroad from Seward on the Gulf of Alaska.

aska

Conditions Affecting Navigation

During the period of nearly half a century in which
Yukon River has been the principal avenue of transportation,
its navigation has presented many problems. Above Fort
Selkirk, the river flows through country covered by former
glaciation, and during the melting of the ice-cap, it had a
considerably larger volume of detritus to carry. As a
result, the valley above Fort Selkirk was choked with this
material and the river is now confined largely to a single
channel which is floored by coarse gravel. Below Fort
Selkirk the banks are lower and composed of fine material.
The section of the river situated in Yukon Territory is
comparatively shallow, and this condition, combined’ with
the speed of the current and the crooked channels in various
sections, requires highly skilled pilots for successful
navigation.

The glacial streams, Lewes and White Rivers, which
feed the Yukon, have their highest period of flow in July
and August. The snow-fed streams, such as Teslin,
Pelly, and Stewart Rivers, come quickly into flood at break-
up. By late July or August they depend entirely on rain
for their flow and can become very low. Lewes River,
south of Whitehorse, and lakehead waters in that district
which are glacial fed, are therefore very low at the period
when navigation should start. Conversely, the river below
or north of the mouth of the Teslin, fed by that stream and
swelled by Pelly and Stewart Rivers, is at good navigation
stage. AAs a result of these conditions heavy loadings of
steamers at Whitehorse were not possible until July,
although the river below the mouth of the Teslin was
occasionally suitable for navigation in May.

An improvement in navigation conditions was effected
in 1925 when a dam was constructed across Lewes
River 7 miles below Marsh Lake. This dam is partly
closed after navigation ceases in the autumn and a head of
water is built up throughout the winter. The dam is
progressively opened after May 1, and the release of
the water raises the level of Lake Laberge about 5 feet,
breaking up the ice around the shore and hastening the
opening of navigation. The net results have been to

[ 108 ]

advance the dates of the opening of navigation from White’
horse down river from June 1 to 16, to May 15 to 25:
In addition, whereas it was not possible to handle full
loads of freight from Whitehorse until July 1, owing to
the shallow water at the head of Lake Laberge and low
water in the stretch of the Lewes between the lake and
Teslin River, the first boats downstream from Whitehorse
are now able to carry full loads. The break-up of the ice
in Lake Laberge is, therefore, the key to the date of the
opening of navigation. The volume of water also has a
bearing, but in normal years this is not a factor (6).

As no systematic survey of channels in Yukon River has
ever been made, it is impossible to estimate average depths
of the various stretches of navigable water. However,
officers of the White Pass and Yukon Route have estimated
the minimum depth of the navigable channel of the Yukon
at low water stage from Whitehorse to Dawson, and from
Dawson to Nenana, Alaska, to be about 4 feet. The
minimum depth of Stewart River channel from Mayo
to its intersection with the Yukon has been estimated at
low water stage to be about 3 feet (6).

_ Lewes-Yukon Rivers

Navigation on the Lewes-Yukon system is hazardous
at several points and although most of the improvements
made to date have been undertaken by the principal trans-
portation company using the river (White Pass and Yukon
Route), additional work required to improve the channel
is being considered by the Federal Department of Public
Works. On the upper river, navigation from Lake Bennett
through Lake Nares to Tagish Lake is hampered at times
by silt which is deposited in the channel between Lakes
Nares and Bennett. The silt is brought down by Watson
River, which empties into Lake Bennett just west of Car-
cross, and carried by currents and wave action into the
narrow channel of the Lewes which deposits it at the
entrance to Lake Nares. This silting, if permitted to
continue without remedial action, might eventually become
a serious navigation hazard. In 1944, the Dominion Depart-
ment of Public Works investigated a proposed remedial
scheme which involved diversion of the headwaters of the
silt-carrying Watson River into Wheaton River, which
enters Lake Bennett some 12 miles southwest of Carcross.
Owing to the amount of construction work involved, the
scheme was not approved, but a dredging program was
recommended instead.

Another difficult stretch is that situated between Lake
Laberge and the mouth of the Teslin, known as the “Thirty-
mile” River, which contains several boulder-strewn riffles
or shallow rapids. Some work has been carried out on
this section annually, but it will always present a problem
as anchor ice, freed from the river bottom in spring, some-

times carries rather large boulders with it and deposits
them at various points.

At Five Finger Rapids, only one of the channels has
suficient depth of water for navigation, and through this