Waterclarity

Waterclarity is a measure of how transparent water is to light. It depends on the amount and properties of suspended particles such as sediment, plankton, algae, and dissolved substances that absorb or scatter light. Waterclarity influences ecological processes, heat absorption, and the suitability of water for drinking, irrigation, and recreation.

Common metrics include Secchi disk depth, turbidity measured in nephelometric turbidity units (NTU), and total suspended solids (TSS). The Secchi depth is the distance at which a black-and-white disk disappears from view when lowered into water; deeper readings indicate clearer water. Turbidity gauges quantify light scattered by suspended particles; higher NTU indicates murkier water. Absorbance and attenuation coefficients describe how colored dissolved substances affect clarity, especially in relation to light penetration.

Clarity varies with weather, season, land use, nutrient inputs, and biological activity. Rainfall and river discharge can increase suspended solids, while algal blooms can alter light penetration depending on nutrient status. In natural lakes, Secchi depths can be several meters, whereas rivers exhibit more variability and can change rapidly with flows and sediment input.

For ecosystems, light penetration governs photosynthesis, aquatic plant growth, and habitat suitability for benthic organisms. For drinking water and recreation, clarity affects treatment efficiency, aesthetic quality, and perceived safety. Excess turbidity can shield microbes from disinfection and transport contaminants attached to particles.

Water managers monitor waterclarity using in situ sensors, sampling programs, and remote sensing to track trends and assess compliance with guidelines that regulate turbidity and related water quality measures.