Cantonal Council ZG Cantonal Council anchors measure for Lake Zug aeration in the structure plan

The Zug Cantonal Council unanimously approved various amendments to the cantonal structure plan on Thursday. One of these concerns the planned aeration for the sustainable restoration of Lake Zug, which has met with criticism from fishermen.

With a phosphorus content of almost 80 milligrams per cubic meter, Lake Zug is still in a highly nutrient-rich state and therefore well above the legally required value of 30 milligrams per cubic meter, as the government's report and proposal show.

Phosphorus is mainly used as a fertilizer. Excess phosphorus accumulates in the soil. During rain or soil erosion, phosphorus can enter bodies of water, which promotes the growth of algae and plants, especially in lakes.

Lake-external and lake-internal measures

In order to restore Lake Zug sustainably, measures are planned both outside and inside the lake. As the in-lake measures have an impact on space and the environment, they must be anchored in the structure plan. Measures external to the lake are better settlement drainage and measures in agriculture, which have already been addressed.

A so-called circulation support is planned within the lake. This enables the absorption of oxygen in the deep water. Compressed air is to be pumped into the southern lake basin in winter by means of a compression system in order to restore the natural circulation of the lake. This process removes the phosphorus depot in the deep water from the lake in a controlled and slow manner via the Lorze and at the same time enriches the deep water with oxygen.

Council welcomes aeration measure

The SP parliamentary group explicitly supports the measures within the lake, as spokesperson Barbara Gysel said. Lake restoration is a complex issue "that will continue to occupy us", she said. But the measures outside the lake are also important in order to address the causes, Gysel emphasized.

The GLP parliamentary group considers the planned aeration measures to be "sensible", as Martin Zimmermann (GLP) said. "Unfortunately, however, it seems to have taken the federal government again to give us a leg up," he criticized. He would have liked the canton to have been "more proactive" here.

The FDP parliamentary group was of the opinion that the measures already taken outside the lake were not sufficient and that additional measures within the lake were necessary, as spokesperson Thomas Gander said.

The proposed solution was seen by the FDP parliamentary group as "a possible way forward", but its effect would only be seen in a few years' time. Depending on technical progress, other solutions are also conceivable for the FDP in the future. "Ideally, the nutrient-rich phosphorus from the lake can be mined for further use," said Gander.

Erich Grob (center), board member of the Zug Farmers' Association, also emphasized this: "It would be desirable if the phosphorus could be skimmed off and reused."

The ALG parliamentary group welcomed the measures within the lake with the planned aeration, as Andreas Lustenberger said. "Today, we are tackling a legacy from previous generations and investing in a clean Lake Zug for future generations," he said. He also emphasized that regeneration would not happen overnight.

Critical fishermen

Adrian Risi (SVP) regretted that the fishermen did not agree with the aeration. He hoped that they could be brought on board.

Jean Luc Mösch (center), board member of the Zug Cantonal Fishing Association, hoped the same. There is no doubt that something needs to be done to reduce the phosphorus content in Lake Zug, he said. However, the professional fishermen did not feel that they were being properly addressed.

The cold season in particular is the fishing season for Zug rudd and lake trout, Mösch explained. Any disruption to these "very sensitive fish species" as a result of the planned measures within the lake is a real possibility and must be prevented. According to Mösch, information and experience reports for fishermen are "imperative".

Renaturation projects and forest nature reserves

Further adjustments to the structure plan concern new forest nature reserves, new renaturation projects on watercourses and lakes, freight traffic and the Rotkreuz Süd highway semi-exit.

The structure plan also includes various applications from municipalities resulting from their local planning revisions. These include Unterägeri, Oberägeri and Neuheim.