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Saturday, 21 Oct 2017

Suorva dams

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Seepage evaluation from two Temperature Measurements

Optical fibres have been installed at two of the dams at Suorva in order to further improve the monitoring of the largest man made reservoir in Sweden. (Suorva is a 60km long regulated reservoir with a total capacity of 5.900x106m3 which has an annual energy production of ca 6100GWh).

The Sourva dam is positioned in the upper part of the Lule älv River in the mountainous region of Sweden to the north of the polar circle. Construction of three rock fill embankment dams: Eastern, Western, and Sågvik dam was completed in 1972. The fibre optic installations in 2004-2005 were made in order to measure movements (strain) on the crest of the East and West dams, and the seepage flow of the West dam. The strain measurements are included in a research project funded by Elforsk AB.

Installations for Seepage Measurement at the West Dam

The West dam is 76m high. A support toe berm was constructed in 2004-2005 which includes a fibre optic cable. This cable has been installed at various elevations along the length of the downstream toe to provide a good quality seepage measurement.

Result

Evaluation of a single measurement showed minor seepage flow at the rate of between 10-60ml/(s,m) at the lowest seepage levels, based on measurements taken by several fibre optic cables. A second measurement made in May 2006 confirms these seepage flow rates. One example is shown in the figure which shows good agreement for simulated and actual measured temperatures at flow rates of about 25-30ml/(s,m). Further measurements in the West dam would help us to further attain a more accurate rate of seepage flow as well as flow changes.