Heavy rains led to record-high discharges in Oulujoki River
Residents will be compensated for damage on a-case-by-case basis
By Tapio Mainio in Oulu
Electricity supplier Fortum, which runs the hydropower plants on the Oulujoki River, has had to resort to record-high discharges as a result of exceptionally heavy precipitation in the summer.
”For 60 years, such high discharges have not been seen in the Oulujoki River”, report pensioners Inkeri and Ahti Lämsä, walking across dam bridges in Oulu.
The water level in Oulujärvi, the lake that serves as the water supply of the power plants, has already been higher than permitted for the past week or so.
On Monday, the water level in the lake rose 10 centimetres above the maximum permitted level, which is 123.20 metres above sea level.
”All dam hatches have been opened, and water is being discharged into the sea at a speed of about 850 cubic metres per second. Only about half of the water actually flows through the turbines of the power plant”, reports project engineer Ville Airovuo, from the local power company Oulun Energia.
The water that flows through the flood hatches does not produce electricity.
”The flood has caused all kinds of trouble. Boats and piers belonging to cottage-owners have got loose and sunk. The electricity company should have started flow diversions in good time, rather than at the last minute”, says Matti Väisänen, who operates a chain-ferry on Oulujärvi.
According to Fortum, the discharges from the 928 sq.km. lake, which is Finland's fifth-largest by area, have been more than double since mid-July, compared with regular water transfers in the summer.
”After heavy rainfall, the amount of water flowing into Oulujärvi was around 1,250 cubic metres per second, which is more even than in the summer flood of 1995, when the amount of water comin into the lake was 1,000 cubic metres per second,” reports Timo Aaltonen from Fortum’s monitoring room in Espoo’s Keilaniemi.
According to Aaltonen, the electricity utility will compensate for the damage caused to residents on a-case-by-case basis.
On the other hand, Fortum will not have to pay fines for the overly high water level caused by exceptional circumstances, reports Kari Pehkonen from the unit of the Kainuu Centre for Economic Development, Transport and the Environment.
”We will also have to investigate whether the water level could be raised temporarily in the Kiantajärvi and Vuokkijärvi lakes in order to lower the level of Oulujärvi. We will also have to find out whether we could prepare ourselves for sudden rains by changing the regulation practice”, Pehkonen notes.
”In the case of Kiantajärvi, the lake water level is close to the permitted limit. If it starts to rise any higher, it threatens to erode the historic Kalmosärkkä sand ridges in Suomussalmi”, says Mikko Juntunen, a summer resident in the Kiantajärvi Lake area.
The area was inhabited already more than 4,000 years ago.
The regulation of the waters of Oulujärvi started in 1951, that of Nuasjärvi at the end of the 1940s, and of Kiantajärvi in 1959.
The original aim of the regulation was to divert the flow of water to local power plants, which would serve the interests of hydroelectricity as efficiently as possible.
Another aim was flood protection. The current regulation limits have been ordered for Oulujärvi in 1974, for Nuasjärvi in 1961, and for Kiantajärvi in 1964.
The limits are not completely binding, but exceptions can be made for example in order to prevent the formation of sludge dams.
Helsingin Sanomat / First published in print 14.8.2012
Previously in HS International Edition:
Lapland´s flood peak expected in late May (14.5.2012)
Spring floods causing trouble in river areas in Western Finland (3.5.2012)
TAPIO MAINIO / Helsingin Sanomat