The cleanest lake in the world

Located in a national park, Blue Lake holds the title of the cleanest lake in the world.

In 2011, the New Zealand National Institute of Water and Atmospheric Research (NIWA) conducted scientific experiments and suggested that Blue is the most natural lake among the fresh water sources known to man.

According to NIWA research results, the view in the lake is over 80 meters away, which can be considered as "clear" Blue water as distilled water. This lake has a characteristic blue-purple color that exists only in clear natural waters. Further testing showed that Blue Lake was also clearer than most of the Earth's seawater, except for some areas of the South Pacific around Tahiti and Easter Island.

As part of Lake Nelson National Park in the South Island, Blue Lake receives water from nearby Lake Constance thanks to an underground river system.(Photo: Klaus Thymann / Project Pressure).

Blue Lake is located at an altitude of 1,200 meters above sea level, so the water in the lake is always cold 5-8 degrees C. For hundreds of years, Ngati Apa ki te Ra To - a native Maori ethnic group, considered it a in sacred lakes called Rotomairewhenua, or lakes of peaceful lands.

Traditionally, the Maori Aborigines used water in Blue Lake to wash the bones of deceased men from the tribe. Women's bones were cleaned in the nearby Lake Constance. The ceremony of sending souls to the afterlife is carried out on the journey from Lake Blue, along a sacred road, to the headland of Farewell. The last remains are buried in the Sabine Valley.

Kiley Nepia, cultural manager of the Māori people on the South Island, said he felt a spiritual connection to Lake Blue when he first came here. " I really understand why our ancestors chose that lake to perform the rituals. When you get there, you will feel really serene. Like the baptismal water, or the blessed water of a church, These are holy waters for the people of Ngati Apa ki te Ra To , " Nepia said.

Almost Blue Lake is not covered by trees.(Photo: Klaus Thymann / Project Pressure).

The farthest view of the lake is 81.4 meters, and is stable at 70 - 80 m. Dr. Rob Davies-Colley, NIWA scientist, said: "I think there is not much difference between the water of Blue Lake and pure water. And if anywhere there is clearer water, it can only in a little more ".

Why Blue Lake water is so clear is still a mystery. Water comes from Lake Constance through an underground river and flows from streams about 35 meters high from Lake Blue. However, Lake Constance at an altitude of 1,335 m is almost not so.

Therefore, the water flow between the two lakes must undergo natural filtration process underground. Scientists believe that water passed through ice gravel from the last ice age (about 12,000 years ago) and debris from landslides. These layers of matter act as a screen for particles and organic matter in water. Blue Lake also has a self-defense mechanism when it discharges water every three days, which means that any nutrients or pollution is washed away.

Blue Lake may temporarily become cloudy when heavy rains wash away soil and rock into the lake bed, but after a few days the water is clear.(Photo: Klaus Thymann / Project Pressure).