Hylte Dam – Fibre Installed In Trench In Dam

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HYLTE DAM – FIBRE INSTALLED IN TRENCH SPECIFICALLY CONSTRUCTED FOR SENSING CABLE

Optical fibre cables were installed in late 2002 by the dam owner (EON Vattenkraft
AB). The cable is placed at a depth of between 0.8 and 1m, all along the dam toe, close to or just below the ground water level.

The purpose of this installation is primarily to identify areas with higher seepage, or
increasing seepage, but also try to estimate the seepage flow.

Five measurements have been performed since 2003. Three of these have been done just for a few days, while two longer periods were measured during winter 2003-2004 and summer 2005. The result shows generally a higher temperature in the summer than in the winter.

Hylte_Dam

The sections where the fastest cooling occurs during the winter period are observed at chainage 50, 90, 145, and 190m. These areas also correspond to those where the temperature is highest in the summer, which can be explained by higher seepage.

Hylte_Dam2

The measurements can also be compared with calculated temperature for different seepage flow rates using the software DamTemp. The seepage flow through the Hylte dam was evaluated from the measured temperatures in two different ways. The first method calculates the maximum measured temperature difference during the measuring period. The seepage flow rate can then be estimated. The other method is based on the measured trend from the long term measurements in 2003/2004. The two methods give a similar flow varying between 5 and 15×10-6m3/s,m, as showed in the figure.

Hylte_Dam3

To discuss your particular requirements please contact Sensornet or visit HydroResearch at www.hydroresearch.se or call them on +46 8 756 4950.