Katana VentraIP

Water clarity

Water clarity is a descriptive term for how deeply visible light penetrates through water. In addition to light penetration, the term water clarity is also often used to describe underwater visibility. Water clarity is one way that humans measure water quality, along with oxygen concentration and the presence or absence of pollutants and algal blooms.[1]

Water clarity governs the health of underwater ecosystems because it impacts the amount of light reaching the plants and animals living underwater. For plants, light is needed for photosynthesis. The clarity of the underwater environment determines the depth ranges where aquatic plants can live.[2] [3] [4] [5] Water clarity also impacts how well visual animals like fish can see their prey.[6] [7] [8] [9] Clarity affects the aquatic plants and animals living in all kinds of water bodies, including rivers, ponds, lakes, reservoirs, estuaries, coastal lagoons, and the open ocean.


Water clarity also affects how humans interact with water, from recreation and property values to mapping, defense, and security. Water clarity influences human perceptions of water quality, recreational safety, aesthetic appeal, and overall environmental health.[10] [11] Tourists visiting the Great Barrier Reef were willing to pay to improve the water clarity conditions for recreational satisfaction.[12] Water clarity also influences waterfront property values. In the United States, a 1% improvement in water clarity increased property values by up to 10%.[13] [14] [15] [16] Water clarity is needed to visualize targets underwater, either from above or in water. These applications include mapping and military operations. To map shallow-water features such as oyster reefs and seagrass beds, the water must be clear enough for those features to be visible to a drone, airplane, or satellite.[17] [18] Water clarity is also needed to detect underwater objects such as submarines using visible light. [19] [20] [21]

Water clarity vs. water quality[edit]

Water clarity is more specific than water quality. The term “water clarity” more strictly describes the amount of light that passes through water or an object’s visibility in water. The term “water quality” more broadly refers to many characteristics of water, including temperature, dissolved oxygen, the amount of nutrients, or the presence of algal blooms. How clear the water appears is only one component of water quality.[1] [5] [47]


An underwater ecosystem can have high water clarity yet low water quality, and vice versa. Scientists have observed that many lakes are becoming less clear while also recovering from acid rain. This phenomenon has been seen in the northeastern United States and northern Europe. In the past, some lakes were ecologically bare, yet clear, while acidity was high. In recent years, as acidity is reduced and watersheds become more forested, many lakes are less clear but also ecologically healthier with higher concentrations of dissolved organic carbon and more natural water chemistry.[48] [49] [50]

Beer-Lambert law

Color of water

Forel-Ule scale

Ocean color

Ocean optics

Secchi disk

Turbidity

Visibility

Water quality