State of water on the surface of Lake Zug good

A recent report published jointly by Eawag, the water research institute of the Swiss Federal Institute of Technology in Zurich and the Office of Environmental Protection of the Canton of Zug (AUSKZ), showed that the quality of the water of the lake has been improving steadily over the years though it will not be entirely healthy, so-to-speak, until the next century. One problem is the phosphorous content of the water in the deeper parts.
 
This latest report showed that, for every cubic metre of water, there is 80 milligrammes of phosphorous, due largely to excessive levels of nutrients from agricultural activity formerly flowing into the lake. In order for the lake to be regarded as totally healthy, this level of phosphorous content needs to be reduced to 30 milligrammes per cubic metre. The last time it was at this level was at the beginning of the 19^th century.
 
The current target is for it to return to this state but, as Bruno Mathis, the head of the water department at the AUSKZ explained, the flow-through of water in Lake Zug is very sluggish. Indeed, it takes 14 years before it is totally renewed and, in this respect, it is not unlike Lake Geneva and Lake Sempach in the canton of Lucerne. Furthermore, on account of Lake Zug’s depth, the water never really totally changes, so it is estimated that only in 2100 will the quality of the water be that what it was 200 years ago.
 
One other adverse effect of the cold water with its high phosphorous content lying in the depths of the lake, a state which is actually accentuated by climate change, is that the oxygen level, in these deeper parts, is also very low, and this, of course, has an adverse effect on fish, limiting their habitat. This means that water below a depth of 120 metres has so little oxygen that fish cannot breed naturally there. “To think that the lake will not return to its healthier state until 2100, unless additional measures are undertaken, is rather a sobering thought,” said Mathis.
 
By “additional measures”, he was referring to artificial aeration of the lake and the draining-off of water at the lower depths, all very complex, expensive and politically controversial. What was central to the improvement of the quality of the water was the continuation of ongoing measures on land in the near vicinity of the lake to ensure fewer nutrients from agriculture ending up in it.
 
On a more optimistic note, Mathis concluded that the quality of the water for bathing purposes was very good. And what a marvellous sight it has been in recent days as storms whipped up its surface.
 
This article was written prior to the tragedy which occurred off Hünenberg this week.