the fishing zones
rules & licenses
Power plant Tolga
Hydroelectric power plant in River Glomma
During summer 2018 the final decision was made to build a hydroelectric power plant in
Glomma just upstream of Tolga. Let me try to explain what this means for
Kvennan Fly Fishing.
A few km upstream of Tolga village a small dam will be constructed. A
reservoir will be formed with a capacity of 10.000 m3. From this
reservoir a part of Glomma’s water will be drained into a to be
excavated tunnel, going all the way down to Eidsfossen (the beginning of
the Fly Fishing zone), where the water is spilled back in the river bed
again. The difference in altitude between the water outlet at the dam
and the Eidsfossen falls is about 88 meter.
The build of this power plant
has started in September 2018 and it will be finished during 2021. Total
costs involved are 582 million NOK or about 60 million euro. The plant
will generate on average 205 GWh per year, enough to provide 10.000
Norwegian households with electricity.
In the tunnel there will be three turbines, each with a maximum
capacity of 20 m3/sec. The tunnel will be about 12 km long, and ca 7
meter wide. The power plant will have a maximum capacity of 60 m3/sec.
In summer time a minimum flow of 12 m3/s has to remain in the river bed,
in winter time minimum flow is 7 m3/sec. Normal summer level in Glomma
at Hummelvoll is about 50 m3/s . The minimum flow in the
affected river section is 12 m3/s , so the power company, named Eidsiva,
can take maximum 38 m3/s into the tunnel. They could use the extra
capacity of the reservoir (10.000 m3) to use the maximum capacity (60
m3/s) of the plant. The reservoir would drain with 60 – 38 = 22 m3/s. In
8 minutes the reservoir would be empty. Common sense tells me this is
not going to happen very often, and sudden changes in water level in the
KFF zone will only happen if it rains a lot. Just like before.
The construction of the power plant, dam, tunnel and outlet at
Eidsfossen will take about three years. Pollution of Glomma, caused by
the build of the dam, seems to be avoided by the use of temporary dams.
The biggest part of the job will be the excavation of the tunnel and the
build of the machinery in the tunnel. This has no impact on the river.
It’s also good to know what we are talking about, when it comes to the
relation between water level and flow. During the last years I have been
collecting data, and I found out that a change in water level (at the
Hummelvoll measuring point) of 10 cm corresponds with a change in water
flow of about 10 m3/s. This 10 cm change at Hummelvoll will give a
change of about 4 cm in the Fly Fishing zone at Kvennan camp. The reason
for this is simple: Glomma flows faster and the river bed is much wider
at the campsite, compared to the rather deep, narrow and slower flowing
section at Hummvoll.
The part of Glomma between the dam and the Eidsfossen falls – the so
called Tolga zone - is going to be affected badly by the power plant,
especially because of the relatively small amount of water in the river
bed during mid summer and winter.
But for the Fly Fishing zone not so much will change, I think. The water
that was taken out of the river, and into the tunnel, is back in the
river again. There can be some small changes in water level when the
power plant is in production, but I guess they will not have much impact
on the fishing conditions at Kvennan Fly Fishing. There might be a small
effect on water temperature – I heard someone say 0,5 degrees Celsius.
All in all, this power plant is not improving things, but I am quite
confident during the coming years KFF will remain one of the best stretches for fly fishing
in famous and beautiful river Glomma.
Hein van Aar, November 2018