Wehra reservoir - Where the water begins its ascent

Wehra reservoir was created between 1971 and 1974 as the lower reservoir of Wehr underground hydropower plant. When the reservoir is full, it is two kilometres long, up to 185 metres wide and has an active storage capacity of 4.3 million cubic metres of water.

Wehra reservoir is connected to the cavern that houses the machine hall of Wehr pumped-storage power plant via a 1.5-kilometre-long tunnel. From here, there is a hydraulic connection via a pressure tunnel to Hornberg reservoir, which lies 600 metres higher up. The water moves back and forth between both reservoirs by either being pumped up from the bottom (for power storage) or down from the top (for power generation).

The Wehra flows into the reservoir in the north. In turn, this water quantity then flows into the lower course of the river. At the end of the Wehra tunnel built for this purpose, a small-scale hydropower plant uses the energy of the river to generate additional renewable energy.

Energy transition

Being able to store electricity in large quantities and generate it within seconds when needed is now more important than ever. The sun and the wind have long been playing their part in generating electricity in Germany and are producing an ever increasing share. Yet these generation sources fluctuate depending on the weather and are unreliable. Pumped-storage power plants come into play when too much electricity overloads the grid or a lack of electricity threatens the supply. They work within seconds, produce zero emissions and generate outputs that rank them among the best of all available storage technologies.

How pumped-storage power plants work

Pumped-storage plants consist of an upper and lower basin. Between them are power plants, which pump water uphill if there is excess electricity and allow it to flow down again through turbines to generate electricity when power is needed. They are precisely tailored to meet the needs of the grid at all times. As such, they help to secure the supply – cleanly, effectively and reliably.

Schluchseewerk AG

With its five pumped-storage power plants, Schluchseewerk AG is one of Germany’s largest suppliers and leading experts. As a partner to its shareholders, it oversees the safe and reliable operation of all its facilities, thereby helping to stabilise the power grid and playing its part in safeguarding the energy supply for today and tomorrow. Schluchseewerk – we are driven by water!

The Hotzenwald Power Plant Group

With two large underground pumped-storage power plants, Schluchseewerk AG’s Hotzenwald Group is rather exceptional. That’s because its huge pumping and power generation machines are housed deep within the mountain in artificial caves, so-called caverns. The advantage lies in the possibility of letting stored water from the upper reservoirs fall almost vertically onto the powerful turbines at the highest possible pressure. The use of potential energy simply cannot be any more effective.

Facts and figures

• The Wehra Dam: Crest length 235 metres, crest width 5.3 metres, height 50 metres above the foundation bed
• Top water level: 419.90 metres above mean sea level; drawdown level: 395.00 metres above mean sea level
• Water surface when full: 25.5 hectares (roughly equivalent to the area occupied by 18 football pitches)