Continuous monitoring of turbidity fluctuations in
coastal and inland waters
Hurricane Zeta resulted in highly turbid coastal waters due to a massive increase in sediment transport. Data from Sentinel-2 01/11/2020
What is turbidity?
Turbidity is a measurement of the clarity (or murkiness) of water due to suspended particles. When suspended particles are present in the water column light is scattered, reflected and attenuated rather than transmitted in straight lines. Turbidity is an optical property which quantifies the degree to which light is scattered and absorbed by the particles. The higher the degree of scattered light, the higher the turbidity.
Suspended and dissolved matter that can cause water to be turbid include silt, fine inorganic and organic matter, algae, POM (Particulate Organic Matter), plankton and other microscopic organisms. Potential sources of such particles include natural sediment resuspension due to high rainfall, wind, waves and tidal runoff, shoreline erosion, wastewater outfalls and other human activities such as dredging.
A range of organic and inorganic particles contribute to the suspended solid concentrations in coastal & inland waters.
Why measure turbidity?
Turbidity is one of the most important indicators used to assess the environmental status of water bodies. Increases in turbidity levels from natural or anthropologic influences may have adverse effects on water quality. Through light limitation, sedimentation, and eutrophication high levels of turbidity can have a significant impact on coastal and inland water ecosystems. When sunlight penetration is significantly reduced, there is a reduction in the visual range which can greatly affect predator-prey interactions in the water. Photosynthesis is also reduced, which in turn can result in dissolved oxygen depletion which further reduces productivity. Additionally, tracking fluctuations in turbidity is key to monitoring sediment plumes from dredging and dumping activities. Conducting turbidity monitoring prior to, during, and after all dredging and coastal engineering activities provides us with a complete picture of possible adverse effects in the area.
Turbidity is a key monitoring parameter for natural and human activities. Flood events, wastewater outfall locations and dredging activities need to be closely monitored.
How we monitor turbidity
Turbidity is measured by specialised optical equipment in lab environments or deployed in the water column. Light is directed through a water sample and the amount of light scatter is measured. The unity of this measurement is a Nephelometric Turbidity Unit (NTU). One of the key prohibitive barriers for conducting turbidity monitoring is the high cost of turbidity sensors, deployment expertise and maintenance labour. A-WaMS aim to overcome this obstacle and provide a low-cost yet reliable sensor along with an easy to access information output delivery system.
The optical sensor (OCS 2) developed by DCU Water Institute, measures turbidity and a wide range of other environmental parameters. The sensor uses light scatter measurements at different angles and multiple wavelengths to provide information on total suspended particle concentrations. Coupled with measurements collected from other detectors present on the sensor (fluorescence or attenuation) and data analytics tools, the sensor aims to classify and identify pollution events in coastal areas in near-real-time. We have the infrastructure and expertise to deploy in a wide range of onshore and offshore environments.
The A-WaMS optical sensor may be deployed on a range of onshore and offshore platforms.
The design of our reliable and robust system not only allows for spot monitoring but due to its low-cost empowers organisations to purchase and deploy a network of sensors in their area of interest. A-WAMS will see the commercialisation of the DCU Water Institute’s optical sensor technology, and integration with the advanced data analytics capabilities of TechWorks Marine.
For more information, please see our project background page –