There are 40 floating islands on the dam in Jablonec to purify the water<

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The grassy islands were installed on the surface of the reservoir by the Liberec company Photon Water Technology (PWT), with which the Jablonec municipality has been cooperating in the fight against cyanobacteria since 2019. According to the company's director Petr Kvapil, floating islands are root water treatment plants that have multiple functions. "On the one hand, the islands, with their root system, drain nutrients from the water and slightly overshadow the water column, thus narrowing the scope for the development of cyanobacteria and algae," he said. At the same time, according to him, the roots of vegetation islands provide shelter and conditions for the development of zooplankton and other organisms competing with cyanobacteria and algae with a positive impact on the overall biodiversity of the water area. The green islands are located near the dam between the first and second reservoirs. “They are arranged in a chessboard to cover as much water as possible. Forty islands will cover about 600 square meters, "added Kvapil.

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The Jablonec dam with an area of ​​27 hectares is a popular place for swimming not only for the inhabitants of Jablonec, but also people from a wide area come there. Up to 5,000 people go to it every day on hot days. The city started fighting cyanobacteria after 2018, when they were temporarily banned from swimming due to their proliferation at the end of August. This year, it is the third element of measures against cyanobacteria on the cascade of the Mšenská dam. "The first was the drainage of the surroundings of all three dams, the second measure is floating pontoons with ultrasound technology on the area of ​​the first dam," said Petr Roubíček, Deputy Mayor of Jablonec.

The location of the islands had to be approved by the Elbe River Basin. "So far, we have concluded a five-year contract with the Elbe River Basin, where we will pay an annual lease of a water area covered with vegetation islands in the amount of 14,000 crowns," said Roubíček. This year, the city paid 820,000 crowns without tax for the entire set of measures to eliminate cyanobacteria in the reservoir. "In addition to the floating islands, it was also the installation of ultrasonic equipment, including monitoring of its effectiveness and laboratory tests for phosphorus precipitation, as well as accompanying monitoring in all reservoirs of the dam," added Fričová.