Turbidity monitoring

what is turbidity?

Turbidity is a measure of the suspended sediments in a water body. Sediments in the water can impact clarity, temperature, and the ability of certain organisms to survive. This measurement, taken in NTUs (Nephelometric Turbidity Units), can tell us a lot of things about a system, and generally change with the seasons or what is happening in or near a water body in a given moment. More permanent conditions along a stream contribute to more consistently high or low measurements.

is all turbidity bad?

Not necessarily. Many natural factors can increase turbidity or make water more cloudy, including the presence of beavers, landslides, or large wood installations that slow water down and help contain sediments. Many wetlands’ water often appears quite muddy, but this is a feature of slower-flowing water that can ultimately allow it to be cleaned as it seeps through layers of soils and into rivers, streams, or aquifers.

While some areas of Clatsop County are at risk for high levels of sedimentation that can negatively impact salmon, some research shows that the Columbia River is actually receiving much less sediments than it did historically, which could impact the estuary’s ability to replenish organic matter that washes out in high water events or that is dredged to maintain the channel.