Water Clarity

Measuring water clarity is an effective method of determining the health of a body of water. Water health is critical for any animals that rely on a body of water to sustain life. Areas used for water recreation can also benefit from monitoring water clarity.

Things That Can Impact Water Clarity

Various environmental factors can detrimentally impact ponds, lakes, lagoons, marinas and other bodies of water.

• Erosion
• Nutrient and sediment pollution
• Toxins

How Water Clarity is Measured

Essentially, water clarity refers to how clear the water is. This is determined by measuring how deep light penetrates into the water. Particle suspension in the water impacts this light penetration level. The more solid particles suspended in water, the less light can penetrate. This is because the particles absorb and scatter the light. There are three common methods of measuring water clarity.

• Secchi disk depth

  A small black and white weighted disk is lowered into the water until it’s no longer visible. That depth is measured and noted as the Secchi disk depth for turbidity and water clarity determination. It’s the most common method in use but is easily subject to error. Sun glare and human error can lead to faulty results.

• Nephelometers/Turbidimeters 

  This electronic instrument measures turbidity, also called haze. It refers to the optical quality and color of the water. The test can be performed on-site or in a lab with an optical sensor. The device measures how much light is reflected/scattered in the water. Nephelometric Turbidity Units (NTU) are the official units of measurements for turbidity.

• Total Suspended Solids (TSS)

  Typically, turbidity is the result of TSS. Therefore, measuring the weight of these solids can accurately determine water clarity. The process includes taking a water sample to be filtrated. The filter is weighed while wet, and then dried and weighed again. The difference in weight quantifies the TSS found in the water. Guidelines for this procedure can be found in Standard Methods for Analysis of Water and Wastes.

If you own an aquatic habitat, be sure it can sustain plant or animal life by measuring the water clarity — or if your body of water is used by people for recreational activities, test its water clarity for safety. Visit us here to review our water clarity testing services.