Catchment area upstream from the water project 10,555 km2
Average precipitation – 548 mm
Average annual temperature – 9.6oC
Extreme temperatures – from -35oC to +35oC
Average number of ice days – 33 days
Average annual flow Qa – 150 m3.s-1
Q365 – 27 m3.s-1
Q355 – 36 m3.s-1
Q100 – 1,460 m3.s-1
(Q100 flows are affects by the Orava and Liptovska Mara reservoirs)

Kralova water step
The water step's location was decisively determined by the longitudinal profile of the Vah river channel and the existence of a free area for a reservoir of the required volume. The water step composed of a dam, hydroelectric power plant and a lock is situated on river km 64.025 of the Vah in a place where the riverbed gradient abruptly changes. The step is located in a pierce on the right bank of the meandering Vah. The location was selected so that the water step objects do not disturbe the drainage parameters of the original Vah river channel.

The dam lies on the left side of the water step. It consists of four fields 16 m in diameter. The dam fields are dilatated between one another in the middle of pillars. The fields are dammed with segments with shutters identical in all fields. Control cabins are below the dam crest.

Total length of dam with a stilling basin – 71.9 m
Dam width – 84.0 m
Spillway crest – 115.0 m
Pillar crest – 128.5 m
Total length of shutters – 10.6 m

Makeshift damming is ensured by steel barriers along with the dam construction. Five barriers shut one field. Atop the dam is a bridge serving as a road closed to public.

The hydroelectric power plant with two turbogenerators is in the middle of the water step. It consists of a functional and an installation block. The plant has two Kaplan turbines with a rotating wheel 6,750 mm in diameter. The plant generates electricity during peaks whose guaranteed duration is 4.6 hours a day. The stored water volumes make it possible to extend electricity generation by further 6.9 hours, if necessary.

Main parameters of the hydroelectic power plant:
Turbine throughput – 2 x 210 = 420 m3.s-1
Net heads: minimum/maximum – 9.05/12.45 m
Range of gross heads: minimum/maximum – 9.9/13.0 m
Rated capacity – 45.0 MW
Average annual production – 112.4 GWh

The lock is built on the righthand side of the water step. The lock is structurally divided into three separate units: a top head, central part and a bottom head. From a static point of view, the lock is a ferroconcrete channel. From the head water the lock is dammed by a steel segment. The segment is 7.3 m high and its bottom threshold is 118.00 m above sea level.

The lock is filled with water through long bypasses with direct filling, and is emptied through short bypasses.

The total lenght of the lock is 195.4 m, useful length is 110 m, inner width 24 m, and the depth is 19.5 m.

Reservoir The Kralova reservoir consists of a dam and perimeter dykes (righthand and lefthand dykes).

The reservoir's parameters:
Total volume of reservoir – 51.9 million m3
Reserve volume of reservoir – 22.3 million m3.
Reservoir area – 11.7 km2
Maximum depth – 15.0 m
Backwater length – 19.7 km
Maximum width of reservoir – 2.0 km

Dyke of the reservoir
The reservoir's righthand dyke is connected at the lower end to the upper waterway of the lock, then continues in the Vah inundation area as far as a short stretch near Unovce Forest where it extends into a protected area. The total length of the dyke is 11,267 m. At kilometer 10.0, the dyke's character changes into a protective dyke as it is not exposed to permanent backwater. The permeable sandy-gravel substratum of the dyke is sealed with underground clay-and-concrete walls. Between kilometers 4.53 and 10.0 the walls extend to a depth of 12 m and are 40 cm thick. Elsewhere the walls are up to 20 m deep and 60 cm thick. In Neogene clays, the wall is only 0.75 m deep.

On the outer side of the dyke are drains and ditches to carry off the water seeping from the reservoir. The drains emply into the Vah below the lock. The drains total 11,450 m.

The lefthand dyke is 12,968 m long, of which the reservoir dyke accounts for 10,484 m, the rest being a protective dyke. The dykes are of the same type as the righthand ones, but the layout of the static and sealing part of the dyke is somewhat different. The underground clay-and-concrete wall extends from the beginning of the dyke near the dam as far as km 5.768. From there to km 10.484 the dyke substratum is protected against seepage by a loam carpet extending into the reservoir .

Waters seeping from the reservoir and partly also surface waters from the protected area are carried off by dewatering ditches and drains totalling 12,181 m.

Information & Contact:

Research Institute of Water Management,
Nabr. arm. gen. L. Svobodu 5,
811 02 Bratislava,
tel.: 00421 (2) 59343111,
fax: 00421 (2) 54415743