Blue water lake is a non-scientific term for a lake with exceptionally high-quality water that, when penetrated by sunlight, appears pure blue.
Blue is one of three main lake colors, the others being green and brown. Water generally absorbs longer, red wavelengths of 600-700 nanometers. Water of the purest quality is able to absorb shorter, blue wavelengths––less than 500 nanometers––deeper into the water column, which scatter and result in the water's deep-blue color. Lake color depends on various properties of the water body, such as nutrient load, algal growth, and overall water quality, as well as the lake's surrounding landscape. These properties, along with the lake's color, can change over time due to human activities and environmental developments. Blue water lakes have minimal amounts of pollutants, algae, and fish. They are commonly located in areas with fast-draining soils and small lake watersheds. Lake color and clarity are measured using a Secchi disk or underwater light sensors.
A long repeated myth is that there are only three blue water lakes in the world: West Okoboji Lake, Lake Geneva, and Lake Louise. The original source of the claim is unknown. It has been said that the claim for West Okoboji Lake originated from National Geographic, but no records can be found to support this. The list of lakes can also possibly be attributed to an early twentieth-century scientific study that compared West Okoboji Lake to Lake Geneva. Other blue water lakes in the world include Lake Tahoe and Crater Lake. The majority of recognized blue water lakes are located in North America, specifically the United States.
West Okoboji Lake, located in Iowa, United States.
Lake Tahoe, located in Nevada, United States.
