Turbidity facts for kids

Turbidity is a way to measure how clear or cloudy water is. It tells us how well light can pass through the water. Water becomes cloudy because of tiny bits of stuff floating in it, like dirt, sand, or even very small living things. These tiny bits are often too small to see with just your eyes. Measuring turbidity is a very important test to check how healthy and clean water is.

Water can have many different sizes of tiny particles floating in it. Some particles are big and heavy enough to sink quickly to the bottom if the water is left still. But very small particles, like those that make water look cloudy or murky, either sink very slowly or don't sink at all. This happens especially if the water is moving or if the particles are super tiny, like colloids.

What Makes Water Cloudy?

Water can become cloudy for a few reasons, both natural and from human activities.

Natural Causes

• Tiny Water Plants: In lakes and rivers, tiny plants called phytoplankton can grow a lot. When there are many of them, they can make the water look cloudy.
• Algae Blooms: Sometimes, algae (another type of tiny water plant) grow very quickly, creating what's called an Algal bloom. These blooms can make the water very murky.

Human Activities

• Dirt and Sediment: When people build things, dig for minerals (mining), or farm the land, they can disturb the soil. When it rains, this loose soil can wash into rivers and lakes. This is called surface runoff, and it carries lots of dirt, making the water cloudy.
• Pollution from Paved Areas: Rainwater running off roads, bridges, and parking lots can pick up dirt and other tiny particles. This polluted runoff then flows into water bodies, increasing turbidity.
• Industrial Activities: Some industries, like quarrying (where rocks are dug up) or coal mining, can release many small rock particles into the water. This can make the water very turbid.

Why is Turbidity Important?

High turbidity can cause problems for both people and nature.

For Drinking Water

• Health Risks: If drinking water is very cloudy, it can be risky for people's health. Tiny harmful things like viruses and bacteria can stick to the floating particles.
• Cleaning Problems: These particles act like shields for the viruses and bacteria. This makes it harder for water treatment plants to clean the water using chemicals like chlorine or UV light. The particles protect the germs, so they might not all be killed.

For Lakes and Rivers

• Less Light for Plants: In places like lakes and rivers, very cloudy water means less sunlight can reach the bottom. This makes it hard for aquatic plants that grow underwater to get enough light to grow.
• Impact on Animals: Many fish and shellfish depend on these underwater plants for food and shelter. So, if the plants can't grow, it affects the animals that live there.
• Fish Breathing Problems: High turbidity can also make it hard for fish to breathe. The particles can clog their gills, making it difficult for them to take in oxygen from the water. This problem has been seen in places like the Chesapeake Bay.

Images for kids

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  Turbidity standards showing different levels of cloudiness (5, 50, and 500 NTU).

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  Turbidimeters used at a water purification plant to measure turbidity (in NTU) of raw water and clear water after filtration.

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  Turbid creek water caused by heavy rains.

See also

In Spanish: Turbidez para niños