EODataBee to support coastal water quality monitoring through high resolution SST development and validation

Capitalizing on the scientific achievements of several FP7, H2020, ESA and national projects (e.g. HIGHROC, GLaSS, Case2Extreme, SIOCS…), EODataBee aims at demonstrating the value of satellite Earth Observation data for coastal and inland water services.

The collection of water samples for analysis in specific laboratories and in situ measurements in pre-defined points have been the most common conventional methods for water quality monitoring. They can provide a very accurate information, but just for particular points in terms of space and time.

Earth Observation satellites have the potential to help overcome these limitations, being a most cost-effective tool for water quality monitoring in coastal and inland waters, as satellite remote sensing data can provide water quality related information over extensive spatial and temporal scales. In this sense, satellite data provide a novel capability to evaluate, monitor and forecast changes of specific water quality products.

Examples of such value-added water quality products, which come from thematic processing of satellite products, are remote sensing reflectance, turbidity, chlorophyll-a concentration, algal bloom detection products, and many others. These are main parameters to control the quality of the water in coastal and inland waters.

EODataBee organizes all spatio-temporal data into DataLayers, a three-dimensional data product (i.e. latitude, longitude and time), which will be acquired from different sources, including Earth Observation (EO), Numerical Models (Model) and in situ. Each DataLayer generated by thematic processing will be quality controlled and re-projected to a user-defined grid enabling direct comparison between different data sources and produce multi-temporal water quality products.

Depending on end users’ needs, EODataBee will work on developing and validation of new Data Layers by scientific experts. An example of the development of such a new DataLayer is a high-resolution sea surface temperature product based on Landsat-8 imagery developed at CEFAS to monitor the impact of cooling water of power plants into a marine environment.

High Resolution Sea Surface Temperature: application to marine discharges

Large marine discharges, such as power station cooling water and wastewater, leave a plume with a different temperature signature. Power stations in particular, abstract seawater at a flow equivalent to that of a small river (15-150 m3s-1), run it through the condensers raising its temperature by around 10°C, and discharge it back again at a different location to avoid re-alimentation at the intake. There are both operational and environmental concerns on the position and intensity of the cooling water plume. Expensive ship-based surveys can only be done infrequently and don’t allow to monitor different tidal and operation conditions.

EODataBee has developed a high-resolution layer (100m) based on LANDSAT 8 TIRS instrument that can give quantitative information of localised features such as these*. Atmospheric correction is crucial in this part of the spectrum and a good knowledge of the transmissivity is needed. Several atmospheric correction algorithms were tested and validated against buoys recording the water temperature 0.5 m below the surface giving an error of better than 1°C. A live data service can provide near real time images of plume intensity and extent, under calibrated conditions, for operational or regulatory usages, at much lower costs and higher availability than in situ surveys.

* The EODataBee also includes a high accuracy SST layer with a spatial resolution of around 2 km, that is better suited for open waters and large-scale features such as ocean fronts.

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Credits: Tiago Silva (Cefas) and Dimitry Van der Zande (Royal Belgian Institute of Natural Sciences – RBINS)

High resolution sea surface temperature maps for the Bristol Channel, where the thermal plume from the Hinkley Point B nuclear power station is visible. The direction and intensity of the plume is greatly dependent on the phase of tide which in the Bristol channel is particularly strong, with a tidal range of 11m at this location.

The top and bottom images were captured during high and low tide, respectively. During the low time the image was automatically filtered to extract dry or very shallow pixels the intertidal flats.