From tracking climate patterns to detecting natural disasters and mapping land use changes, satellites have revolutionised how we collect and analyse environmental data. Using our expertise in Earth Observation at Mallon, we are exploring how readily available satellite data can assist in detecting and tracking environmental issues.
In our latest blog, we explore the use of satellite data to monitor water quality. Taking Belfast Harbour as an example, Mallon colleague Sita Karki compiled the following case study using data captured from the European Space Agency’s (ESA) Sentinel–2 satellite.
Case Study – Monitoring Water Quality in Belfast Harbour
Typically, monitoring water quality can be a resource–intensive activity involving the manual collection of field samples which can be affected by a combination of factors such as manpower availability, accessibility, weather conditions and field safety. This is where Earth Observation (EO), in recent years, has proven to be a more sustainable option for monitoring water quality.
ESA’s Sentinel–2 satellite has been a game–changer in the remote study of water quality. It can capture data over a 290km wide swath of the ground with a revisit time of 5 days and a 10m resolution, which is much higher when compared with other freely available imagery and datasets.
Imagery from Sentinel–2 also benefits from the addition of 2 water quality parameters, Chlorophyll–a Concentration and Turbidity. These are the most commonly used parameters and critical indicators when observing local water quality conditions. Individually, Chlorophyll–a Concentration indicates the growth of phytoplankton growth in the water, and Turbidity shows the presence of suspended or dissolved matter in the water.
For Belfast Harbour, we monitored the water quality over nine months from August 2022 to April 2023. The map below shows the location of Belfast Harbour as captured in August 2022.
Below, the map panel shows the Chlorophyll–a Concentration (mg/m3) for four months. The hot colour (red) represents higher concentrations of phytoplankton growth, whereas the cold colours (blue) represent lower concentrations. The variation in Chlorophyll–a Concentration can be observed along the shallow waters towards the harbour, with higher levels of growth see in the spring and summer months.
Similarly, the panel of maps below shows the Turbidity (FNU) for the same four months. the hot colour (yellow) indicates higher level of suspended matter in the water, whereas the cold colour (blue) represents lower values of matter. As the images show, there is often a higher concentration of matter closer to the shore across the year, but there are periods when this spreads to deeper waters.
What Can We Learn From This?
Earth Observation has enormous potential for the remote monitoring of water levels in specific areas, providing advantages in terms of cost–effectiveness, the area covered and automation. As our maps show, we have been able to track water quality levels across the entire Belfast Harbour area over a 9–month time period. These maps were produced using readily available imagery and can be used to monitor water quality even with limited resources.
However, there are a few limitations to a purely EO–based approach to water quality monitoring. Weather conditions in Ireland and other Northern European states can vary wildly, providing a limited amount of cloud–free days that optical imagery is available. But with limited resources, it can offer a cost–effective way to monitor water quality with periodic water sampling used to validate and calibrate the E)–based results.
Further Information
Please get in touch with us below for further information on the methods used in this case study or to enquire about our Earth Observation services.
