The renovation of Lake Kána in the 11th district may continue

The lake was revitalised last year, so now that the habitat has been rehabilitated, work can begin on reconstructing the sluice, installing the water control system and developing the sediment trap system.

Four lakes, one system

The Kána Lakes consist of four interconnected lakes separated by cross dams. The water flows from the upper lakes through the dams into the lower lakes, ensuring natural drainage.

The lower three lakes each have a contiguous open water surface, while lake number 4 is a so-called wetland, i.e. it functions as a reed bed.

This shallow lake, with its winding channels and aquatic vegetation, serves to filter out sediment and pollutants from the upper waters, significantly improving the water quality of the lower lakes.

Nature-friendly shoreline management for better water quality

An important element of the investment is the shoreline restoration, which modifies the outline of the lake in harmony with the surrounding landscape. The slopes of the lake bed will be modified to a gradient of 1:2, 1:3 and 1:5, creating flatter shoreline surfaces.

This is the solution:

• creates ideal conditions for aquatic plants to establish themselves,
• promotes the development of natural coastal zoning
• and supports the self-cleaning processes of water.

During the works, approximately 5,100 tonnes (approx. 3,000 m³) of hydraulic engineering stone will be installed, while the landscaping of the shoreline will involve approximately 12,512 m³ of earthworks.

Sluice structures for controlled drainage of lakes

Sluice gates are being built into the cross-dams to ensure that the lakes can be drained.

• In dam I, Ø50 cm,
• A sluice gate made of concrete pipes with a diameter of Ø40 cm will be installed in dams II and III.

Total:

• 2 pieces, Ø40 cm,
• One Ø50 cm screw-type pipe sluice will be constructed, supplemented with a control bridge, enabling accurate and safe water level control.

Pump station for complete emptying

The complete emptying of lakes I and II can only be achieved with the help of a new pumping station. The facility will be built in the section of dam I, in the immediate vicinity of the sluice, with a common inlet section.

The pumping station:

• with a total capacity of 400 litres/second,
• It operates with four submersible pumps, each with a capacity of 102 l/s (at a lift height of 3.2 m).

The operation of the pumps is coordinated by a unique PLC control system, as follows:

• they are launched at different times,
• the load on the electrical network is reduced
• and gradual water transport is achieved.

Drainage channel for safe water drainage

The water drained by the pumping station and sluice gate flows into the existing bed of the Hosszúréti stream. For this purpose, a 17-metre-long open-section drainage channel is being built on the downstream side of Dam I.

Into the drain:

• the discharge head of sluice gate I,
• and the four pressure pipes of the pump station are connected.

Sedimentation basin: less sludge in the lower lakes

One of the key elements of the intervention is the sediment trap basin to be constructed in Lake IV, which will be capable of capturing at least one year's worth of sediment. This will significantly reduce the silting up of the lower three lakes.

Main parameters of the pool:

• length: 36 m
• width: 46 m
• depth: 1.5 m
• slope angles:
  • coastal: 1:3,
  • upstream: 1:3,
  • Alvízi: 1:4