The Zillergründl Dam is an arch dam

Arch dam

An arch dam is a type of dam that is curved and commonly built with concrete. The arch dam is a structure that is designed to curve upstream so that the force of the water against it, known as hydrostatic pressure, presses against the arch, compressing and strengthening the structure as it pushes...

 on the Ziller River in the upper Ziller Valley of Tyrol

Tyrol (state)

Tyrol is a state or Bundesland, located in the west of Austria. It comprises the Austrian part of the historical region of Tyrol.The state is split into two parts–called North Tyrol and East Tyrol–by a -wide strip of land where the state of Salzburg borders directly on the Italian province of...

 state, Austria. It is 16 km (10 mi) east of Mayrhofen

Mayrhofen

- Twin towns : Chur, Switzerland Bad Tölz, Germany Bad Homburg, Germany Terracina, Italy Cabourg, France Bad Mondorf, Luxembourg- Transport :Mayrhofen has one railway station, which is located next to the Zillertaler Bundestrasse. The station is a terminus for all Train services operated by the...

. The primary purpose of the dam is hydroelectric power production and it supports a 360 MW pumped-storage power station. As part of the Zemm-Ziller Development, construction on the dam began in 1981 and it along with the Häusling Pumped Storage Power Plant were complete in 1986. The power plant was fully commissioned by 1988. The dam is the second tallest in Austria.

Design and operation

At an elevation of 1850.7 m (6,072 ft) above sea level, the Zillergründl is a 186 m (610 ft) tall and 502 m (1,647 ft) long variable-radius arch dam with a structural volume of 1373000 m³ (1,795,816 cu yd). The dam is 6 m (20 ft) wide at its crest and 36 m (118 ft) at its base. It's reservoir has a capacity of 89500000 cubic metre of which 88800000 cubic metre is active (or "useful") capacity. At normal levels, the reservoir has a surface area of 67 km² (26 sq mi). The reservoir operates at elevations from 1850 m (6,070 ft) to 1740 m (5,709 ft) which is the draw-down level.

Water released from the reservoir reaches the Häusling Power Plant 10 km (6 mi) downstream at 47°08′46"N 11°58′02"E. The power plant is located at an elevation of 1060 m (3,478 ft) and contains two 180 MW Francis turbine

Francis turbine

The Francis turbine is a type of water turbine that was developed by James B. Francis in Lowell, Massachusetts. It is an inward-flow reaction turbine that combines radial and axial flow concepts....

-generators. It is afforded 744 m (2,441 ft) of hydraulic head

Hydraulic head

Hydraulic head or piezometric head is a specific measurement of water pressure above a geodetic datum. It is usually measured as a water surface elevation, expressed in units of length, at the entrance of a piezometer...

given the difference in elevations. Using its pumped-storage capability, the power-station receives water from the Stillupp Reservoir 8 km (5 mi) to the west in an adjacent valley at 47°07′17"N 11°51′58"E and pumps it up to the Zillergründl Reservoir. The pumping and replenishment of the reservoir occur at night, during low energy demand periods. The process is repeated; electricity is generated during high demand periods and pumping occurs during low demand periods when electricity is cheaper.