About the dirtiest lakes

When we plan to spend time at the lake and enjoy the charms that such a stay brings, we increasingly check the state of its water: whether it is clean or dirty. This is not easy, as much has been written about the most beautiful and cleanest lakes in Poland, and not necessarily about the dirtiest. So is the condition of Poland’s lakes so good that this topic can be ignored? What does it even mean that the lake is dirty? Can we say that we came to the lake, given to us by nature 11 thousand. years ago, or do we suggest a common name and soak our feet in a body of water we created ourselves?

How do we know a dirty lake?

The answer to this question is not simple. The condition of lakes is studied and assessed in Poland by the Inspectorate of Environmental Protection. On the website of the Chief Inspectorate of Environmental Protection, which oversees these activities, we can find detailed data and a description of the entire assessment system. This is a rather complex process, and the results are presented in a way that is also not easy to interpret. It is important to note that this assessment is done primarily on the basis of what lives in the reservoir, i.e. the biological elements.

Thus, if the water in the lake is unsuitable for its inhabitants, it can be said that the lake is in a bad state, that is, it is dirty. But lest it be so easy, there are many nuances of this evaluation that determine the final outcome. We write about them expertly in the article: “Are our lakes clean or dirty? Status of lakes in Poland based on monitoring data“.

What are the implications of this? For our use, not much. We can make things even more complicated and say that a lake is dirty when the water from it is not drinkable or when we cannot bathe in it. And here again two completely different classifications come into play.

The first – drinking water is tested primarily for the presence of pathogenic microorganisms, bacteria or chemicals, the consumption of which could be dangerous to our health and life. The second classification concerns bathing areas. In their case, the sanitary inspectorate performs tests primarily for microbiological contaminants, such as coliform bacteria and blue-green algae blooms. The evaluation processes are – as usual – quite complex and involve a number of other indicators.

But… there is no situation without a way out. As I recently heard from a hydrobiologist friend – lake water can be considered dirty if you can’t see your own feet once you enter the lake. And there is some truth in that. The transparency in question is one of the more authoritative optical characteristics of water, understood as the ability to transmit light rays[1]. One of the record holders in terms of low water transparency is Lake Wolickie located in the Gniezno Lake District – the value there does not exceed 0.5 meters. Therefore, we can’t say unequivocally which lake is objectively dirty, as it will be different from the perspective of the needs of the natural ecosystem and from ours – the users.

Which lakes do we know more about?

I have about 7,000 lakes over 1 hectare in Poland. Data on their condition, collected as part of state environmental monitoring, does not apply to every lake. Primarily large lakes – those with an area of at least 50 hectares – are studied. We have about 1,000 of them in the country. Thus, we see that we know nothing about a significant portion of the lakes, which makes it even more difficult to answer the question about the dirtiest ones.

The dirtiest lakes in Poland

Using the aforementioned classification of lakes, i.e. the assessment of water status published by the Chief Inspectorate of Environmental Protection for the period 2016-2021, we can indicate which of the studied lakes are in poor condition. Because the “worst decides” rule applies, and dozens of indicators are evaluated. It happens very often (in about 90% of the lakes) that one of the tested substances determining, for example, the chemical status has exceeded the standards, and then the lake falls into the bag of those with poor condition. However, considering the assessment of the condition in total, it is possible to single out the “dirtiest” lakes ecologically, and these include:

• Lakes: Bytnickie, Lublinieckie, Długie – woj. lubuskie;
• Lakes: Biskupińskie, Żnińskie Małe, Sobiejuskie, Lubieńskie, Ostrowickie – woj. kujawsko-pomorskie;
• Lakes: Klasztorne Duże, Tuchomskie, Dzierzgoń, Słone – woj. Pomerania;
• Lakes: Karaś, Jeziorak Duży, Nidzkie, Brajnickie – woj. warmińsko-mazurskie;
• Lakes: Chociwel, Piaski, Kopan – woj. West Pomerania.

Is it a lake?

Writing about lakes, I can’t help but mention a question that, as a Silesian, I’ve heard many times: what lake do you go to? Some were surprised when I answered that I couldn’t go “at home” to the lake, since there is a lack of them in Silesia. How so? And Lake Goczałkowice? This is not a lake, but a man-made reservoir on the Vistula River. Extremely important because it supplies drinking water to a large part of the Upper Silesian agglomeration, but it is only an artificial reservoir, not a lake. The same is true of Lake Dobczycki in Malopolska, which was created by damming the waters of the Raba River and is a source of water for parts of Krakow. It too has gained prominence through an appropriate name. So is the popular tourist lake Rożnowskie.

So where in Poland to go to the lake?

Poland’s lakes are located primarily in the north of the country, namely in the Mazurian Lake District, Wielkopolska-Kujawskie and Pomorskie Lake Districts. Why? These are mainly post-glacial forms, i.e. occurring in areas shaped by the ice sheet ca. 11,000 years ago.

Lakes are a wonderful gift of nature. They attract lovers of sailing, swimming or camping with their magic. We have beautiful, clear lakes and dirty ones that no one wants to use anymore. This “filth” is primarily the result of nutrient runoff from agricultural fields, causing excessive eutrophication, the discharge of untreated sewage, the creation of waste dumps from lakes, the destruction of riparian vegetation zones and much more. If we do not want to search the keyword “dirtiest lakes” – let’s protect them, very much depends on us.

Did you know that.

The largest lake in Poland is Śniardwy – 113.4 ^km2;

The deepest lake in Poland is Hancza – 108.5 meters;

The longest lake in Poland is Jeziorak – 27.5 km;

The most beautiful lake is the one where you like to spend time. Take care of its condition!

Source:

[1] Hydrogeological dictionary. A collective work edited by. J. Dowgiałło, A. Kleczkowski, A. Macioszczyk, A. Rożkowski. PIG, Warsaw, 2002