Horse Power at
80 Per Cent Efficiency

Ss = — : : — se
ae Ordinary Ordinary
| Minimum | Six Months
Flow Flow
| s =e
RelicamRapid ssi te nwh cpt a a | 142,500 324,000
Mountain Rapids. . . | 80,000 182,000
|
| | =
BR Ota eS ete ert ay eee na 222,500 | 506,000

}

Power Markets——No markets are at present apparent
for the large amounts of power available on the Slave River.
Electro-chemical or electro-metallurgical industries based on
the mineral resources of the adjacent territory would appear
to be the only possibilities warranting the development of
such large sites.

GREAT SLAVE LAKE TRIBUTARIES

Apart from the Slave River, there are numerous tribu-
taries of Great Slave Lake which offer power possibilities
of some magnitude. The drainage tributary to the easterly
half of the lake lies in the geological region known as the
Canadian Shield. The topography is irregular, with
innumerable lakes scattered throughout the area, spilling
over rock barriers into lakes at lower elevation, or descending
steeply by rocky streams. The principal streams are the
Snare, Yellowknife, Beaulieu, and Hoarfrost, which enter
the lake from the north: the Lockhart, which enters from
the east; and the Snowdrift and Taltson, which enter from
the south. The drainage tributary to the westerly half
of Great Slave Lake lies in the northerly extension of the
Great Plains Region. It is underlain by sedimentary rocks
and is generally level in character, except for the relatively
abrupt drop over the escarpment forming the boundary of
the Alberta plateau. The principal tributary in this area
is the Hay River, which enters the lake from the west.
Annual precipitation in the Great Slave Laké basin is light,
averaging about 11 inches. Power resources of the principal
tributaries of Great Slave Lake are described below:

Hay River |7

Y

Hay River, draining an area of 19,200 square miles, is
the largest tributary flowing into the western portion of
Great Slave Lake. It has its source in two main branches;
the Chinchaga River, heading in the height of land that
separates the Fort Nelson and Peace River drainage systems;
and the Kotcho River, heading in Kotcho Lake, which lies
within the Province of British Columbia. From the junction
of these two branches, the river flows in a northeasterly
direction to its outlet into Great Slave Lake. The Hay in

‘general is a sluggish stream flowing through relatively
level country until it reaches the escarpment forming the
boundary of the Alberta plateau, where it descends abru ptly
105 feet over Alexandra Falls and flows through a deep

limestone gorge for a distance of one and a quarter miles to
Louise Falls which has a drop of 41 feet. There is a fall
of 11 feet in rapids extending about half a mile above
Alexandra Falls, and a further descent of 12 feet between
Alexandra and Louise Falls. From Louise Falls to the
mouth, a distance of 43 miles, the river continues first
in the narrow gorge with a swift current broken by rapids
and then broadens out with a moderate current to its
mouth.

Water Supbly—The Hay River derives its water
supply from relatively level country containing extensive
areas of muskeg. The stream is characterized by low water
in the winter months and high water in the late spring and
summer. Discharge records were obtained near the mouth
of the river during two periods, July, 1929, to March, 1930,
and September, 1930; to April, 1931. These records indicate
that the flow fell to a low of 280 c.f.s. in 1931, and 390 c-f.s.
in December, 1939. For purposes of power -estimates
ordinary minimum flow has been assumed at 300 cfs.
and ordinary six months flow at 1,500 cfs.

Power Resources. —A power survey made of Alexandra
and Louise Falls by engineers of the Dominion Water and
Power Bureau in 1921 revealed that physical conditions
were favourable for development at both sites.. It was
determined that by building a dam about 100 feet above the
crest of Alexandra Falls, a total head of 140 feet could be
obtained, and similarly a dam above Louise Falls would
permit a head of 52 feet. Subsequently, however, the
discharge records showed very disappointing conditions of
flow, and opportunities for improvement from storage
appear unfavourable, since any lakes that might be used
as regulating reservoirs are 200 miles or more from the

power reach. The estimates of power available at the two
sites are as follows:

Horse Power at
| | 80 Per Cent Efficiency
Site Head cn
Feet Ordinary Ordinary
Minimum | Six Months
Flow Flow

Zlexandray Halls sees Gee 140 3,800 19,000
otises Hal lst esau eee nn ne 52 1,400 7,000.
Total = 5,200 26,000

Power Markets.—No markets exist at present within
reasonable transmission distance of the power sites on Hay
River. Lead-zine deposits are known to exist to the south
of the western part of Great Slave Lake and to the east of
Hay River. The development of these deposits would
require a considerable supply of power, but it is doubtful

if the resources of the Hay would be adequate for this
purpose.

[79 }