Acid Lakes – A Unique Geological Landscape

An acid lake

What are Acid Lakes?

Generally, lakes are considered to be a source of fresh water. How fresh is your water? Or more specifically, for the benefit of this article, how fresh is lake water?

All water is measured by a scale called ‘pH’, which determines how much of a unit of water is acidic and the acidity rating (pH) is determined by how much hydrogen is in that unit of water.

There is no indication that a reasonable amount of acidic water is bad for you however; indeed, it may have a number of benefits, including being used as a disinfectant and in this world of coronavirus, it may be advantageous to help keep your house and food clean.

The pH range goes from 0 to 14, with 7 being neutral (no acidic content), so pHs of less than 7 indicate acidity. But that does not always mean that water everywhere around the world has a pH of seven. Instead, the pH level in many lakes and rivers are between six and nine.  

But there are certain water systems where the pH of water is less than five. This means that they are acidic and this can be a result of various reasons, but mainly, one can classify them into two main causes. 

  1. The first reason will be the presence of acids in the water or there has been an inflow of acids from some external sources. This occurs when acidic industrial waste is dumped into the rivers and lakes which eventually increases the acidity of the water. Another external source would be acid rain in the region. 
  2. The second reason is simpler. There is a lack of alkaline bases in the water stream.

Acid lakes are often located near areas of granitic bedrocks, siliceous bedrocks and active volcanoes. Certain areas which are marked by researchers as areas which receive acid rain are also some of the common sites of acid lakes. The eastern parts of the US are considered to be areas that receive a high content of acid rain which disturbs the natural alkaline balance in the lakes.

Acid Lakes Around the World 

Some of these lakes are so acidic that the water is strong enough to dissolve a person’s skin. But one of the largest acid lakes is located in Indonesia. Unlike other acid lakes, this lake has turquoise waters that appear to be calm and serene but are actually highly acidic. 

Ijen Volcano, Java 

This volcano complex is located on the border between Banyuwangi regency and Bondowoso regency of East Java. The Gunung Merapi is the highest point of that complex. This name means mountain of fire in the local language. Among this volcano complex is the Kawah Ijen volcano which is a famous tourist attraction. The reason for it being famous is the electric blue glow that comes out of it. The reason for this is the constant sulfuric gas which is present in the volcano. When the gas comes in contact with oxygen in the air, a stunning blue glow is produced. 

Apart from the blue glows, the most important thing which the crater is known for is the world’s largest acid lake it holds. The lake is turquoise in color. It has a yellow tinge to it that makes it even more beautiful. This yellow is basically due to the presence of high sulfur content. On the pH scale, the pH of water in this lake is as low as 0.3 which means it is extremely acidic. You can compare the acidity of this water by the fact that lemon juice has a pH of 2 whereas the pH of water of a car battery is 1. 

It is a crater lake inside around a 12 miles crater in East Java. It lies between the Ijen Volcano Complex which is a group of stratovolcanoes with a long history. The lake around the crater is around 600 feet deep and holds around 1,130 cubic feet of turquoise water. Due to the high acidity of the water, the water is not suitable for drinking purposes and has a pungent, bitter taste. 

However, the lake remains a famous tourist attraction. Though one cannot swim in it, tourists often visit this place to watch the 15 natural waterfalls which connect with this lake and there is a cruise also allows tourists to take a tour of the lake and connecting rivers. However, it is extremely important to take precautions as you cruise through the lake. The high acidity can cause severe allergic reactions on the skin and eyes. In some cases, it can also result in respiratory issues. 

The extreme acidity has affected the nearby river water including river Banyu Pahit. When the water from this lake joins the Banyupahit River, it changes the pH level. According to research done in 2017, it is in a bracket of 2.5 and 3.5 pH on average. There is also a high amount of metal particles such as iron and aluminum. Though the river water is less acidic compared to the lake, it is still not safe for human consumption without treatment. 

The government in Indonesia has taken steps to reduce the acidity of the water. They are using techniques such as filtration and reverse osmosis to increase the pH level of the river. This is done to ensure that the negative impact of acidic water can be minimized. 

As mentioned earlier, the reason for the high acidity of this lake is the presence of high sulfur content. This sulfur provides a source of income to the local population. In fact, most of the locals are associated with sulfur mining. 


There are many other acid lakes spread throughout the world but Ijen volcano Crater Lake is the most acidic lake known on this planet. While the water of the lake is not suitable for irrigation or human consumption, it is a source of employment for hundreds and thousands of people associated with sulfur mining. 

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