General Information
Forty Mile reservoir is located about 25 km (15.5
miles) south of the town of Bow Island on Hwy #879. The maximum water depth is about 23 m
(75 feet) found towards the west dam. Forty Mile reservoir is part of the St Mary
Irrigation District and is an off stream storage reservoir. This reservoir is downstream
from Chin reservoir on the St. Mary main canal system. Sherburne or Grassy reservoir is
also upstream from Forty Mile, however water is diverted "out of" the main canal
into Sherburne so Forty Mile and Sherburne are not directly linked by the canal system.
There are rip rapped dams at both ends of Forty Mile. A small cottage community is popping
up on the west shore near the north end of the reservoir. There is also a campground,
swimming area, boat launch and pier. With the campground being so new it is quite open and
rustic, but when the trees grow a bit taller it could easily become a southern favorite.
The reservoir itself is crystal clear, mostly weedless, and averages about 9-18 metres
(30-60 feet) deep. The relative short distance from Medicine Hat and the town of Foremost,
makes Forty Mile a favorite for boaters and jet skiers and at times the boat traffic can
be busy.
Fishing
Fish can be found from end to end on
this body of water. However, with the lake running from north to south some of the best
fishing is usually found along the east shore, where the strong prairie winds tend to pile
up the forage causing some fantastic feeding frenzies. During the summer the walleye seem
to be very aggressive, responding to faster presentations such as crank baits and spinner
rigs. The winter also produces walleye on a more aggressive techniques such as whistler
jigs and blade baits tipped with a minnow head.
Forty Mile reservoir also contains whitefish, ling cod (burbot) which can be caught readily through the ice, decent numbers of small perch,
and pike, with the occasional monster pike being landed. Be sure to check the
Alberta Sport Fishing Regulations as pike must be a minimum of 63cm. The walleye fishery on Forty Mile reservoir is
open to harvest of one fish over 55cm.
Walleye Stocking History
1990 - 180,650 eyed eggs
1991 - 88,300 eyed eggs
1992 - 78,990 eyed eggs
1993 - 18,000 eyed eggs
Reservoir History
-Contours and Reservoir Map
(New PDF - 1529 KB)
Forty Mile was constructed in mid
1980's and was completed in 1987. The reservoir was filled to capacity in 1989. The design
of this reservoir is a little different than the others in southern Alberta. The water
flow in the main canal as it approaches Forty Mile reservoir can be diverted down the
spillway to fill the reservoir or the flow can run through the siphon across the coulee.
Once the flow crosses the coulee through the siphon the canal then continues on the North
side of the coulee and the flow continues down stream. There is no natural outlet on this
reservoir. Once water has been diverted down the spillway into the reservoir the only way
to remove water from the reservoir is to pump it out. Storage water is pumped out of Forty
Mile at the pump site at the North West corner of the reservoir. Water is pumped up to the
canal on the North side of the coulee then flows down stream. This pump site is expensive
to operate and is only used in drier years. Forty Mile had seen a major draw
down in 2001 the first significant level fluctuation since it was constructed.
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