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Lufuno Vhengani’s rare skills needed for SA’s official coastal #waterquality tool

Lufuno Vhengani has joined the Earth Observation for Water Quality (EO4WQ) team to help build South Africa’s official tracking tool for coastal and estuary waters.

Vhengani is a space scientist in the broadest sense, since he works with data from space satellites, but he is really the critical bridge between earth scientists and the data they use to make sense of the world.

After graduating with a B.Sc degree in mathematics, physics and mathematical statistics in the early 2000s, the Soweto-born technician ventured into electronics engineering. During a training session as part of a post-grad diploma at Stellenbosch University, he was among those who raised their hands to change their career trajectories to ‘remote sensing’.

Remote sensing broadly refers to detecting (sensing) information about the earth from a distance (remote), such as images or measurements taken by satellites orbiting the earth.

In 2007, a few years after completing a specialist diploma in France, Vhengani joined the Council for Scientific and Industrial Research (CSIR), where he is still a sought-after asset as an earth observation technologist today.

Many also think of him as a developer because he’s a self-taught Python programmer, but he’s quick to correct the misconception. “What I really am is a remote sensing specialist who tries to automate things using the Python programming language,” he says.

He made a name for himself in the earth observation community while working on a project to map areas burnt by wildfire using satellite data. His work eventually fed into the Advanced Fire Information System (AFIS) tool, which is very useful in a region like South Africa where wildfires have a big impact on trees and grasslands, and can cause major harm to infrastructure, homes, people and animals.

Vhengani says that as with wildfires and burnt areas, remote sensing can provide scientists with a wealth of information about water quality. For example, they can use satellite data to pinpoint the location of coastal oil spills or invasive plants, and they can monitor sea surface temperatures and harmful algal blooms.

“Unfortunately, satellite images require some expertise in order to process and interpret,” says Vhengani. “The work that we do provides users with information products that can be used to make decisions. This means our users don't have to go into the process of downloading and processing the data.”

“The EO4WQ tool makes it free and easy for anyone to monitor historical or near real-time changes in water quality, using detailed imagery from the world’s best Earth observation satellites," says the project lead Dr Marié Smith.

Like Vhengani, she is also an Earth observation expert at the CSIR, but with an oceanography background. She’s been working with her EO4WQ team to validate satellite data so that Vhengani can automate the way the data is downloaded, interpreted and visualised on the EO4WQ online interface.

“EO4WQ will be able to give users daily updates in lower spatial resolutions for near-real time tracking, using data from the Copernicus Sentinel-3 satellite. But it will also provide incredibly detailed (but less frequent) images taken by the Copernicus Sentinel-2’s sensors to better understand historical changes in smaller water bodies like estuaries,” says Smith.

Smith’s team has identified the algorithms that work best to produce accurate and useful data that non-experts can trust. Now Vhengani is working on automating these algorithms.

He says that while there are challenges on the user interface side of things, the back-end of the EO4WQ tool is working well.

The team hopes that by December 2023, high resolution data on suspended sediments and chlorophyll levels will be available for anyone to access.

“Success will mean we have worked on something different and new, and something that people can find useful,” says Vhengani.

The EO4WQ prototype is currently hosted on the Cyanolakes website, where it will live until it is ready to become the official Water Quality Decision Support Tool for ocean governance, as part of South Africa’s National Oceans and Coastal Information Management System (OCIMS).

EO4WQ is a collaboration between the CSIR, Cyanolakes and OCIMS, and is funded by the South African National Space Agency (SANSA) through their NRF/NEOFronteirs programme.

#water quality #earth observation #csir #SANSA #python #NRF #Cyanolakes #OCIMS #EO4WQ #Dr Marié Smith #Copernicus #sentinel #satellite

River plumes seen over the southwestern Cape region after the heavy rains the past few days. True colour image from VIIRS SNPP taken on 26 September 2023 (NOAA STAR OCView)

Oceanographers go “old school” to check new tech

Believe it or not, but #oceancolour data from satellites are sometimes still validated ‘on the ground’ in the same way it was done nearly 200 years ago - by lowering a Secchi disk down into the water. “A Secchi disk is basically a white, 30 centimeter, weighted plate that you lower down the water column until you can't see it anymore,” says Dr Marié Smith, an expert in marine earth observation at the CSIR.

“The depth at which the disk disappears is the measurement we use for water clarity, or water turbidity.”

Dr Marié Smith (CSIR) out in Table bay doing Secchi disk measurements off the side of a rubber duck motorboat in March 2023. Her team is validating satellite data for EO4WQ by using physical ocean measurements. EO4WQ will become the official Water Quality Decision Support Tool for ocean governance, as part of South Africa’s National Oceans and Coastal Information Management System (OCIMS).

The device is used to measure water transparency in lakes, oceans and fish farms, and was invented by Angelo Secchi in 1865. He was a catholic priest who dabbled in oceanography, meteorology, physics and astronomy.

Smith is also an oceanographer by training, but she uses Secchi disk measurements to calibrate the algorithms that turn vast satellite datasets into simple, easy-to-use snapshots of ocean water quality.

“We need to test if the algorithms we are using actually represent what is happening in South Africa’s waters.

“So, we went ‘old school’- we pick a date and time to go out on a boat to take water measurements when we know it's going to be cloud-free, and when the satellite is going to be flying over directly above us at the same time,” says Smith.

Her team is validating satellite data for the EO4WQ project (Earth Observation for Water Quality), and using these to develop free, online tools for monitoring coastal water quality. EO4WQ will eventually become the official Water Quality Decision Support Tool for ocean governance, as part of South Africa’s National Oceans and Coastal Information Management System (OCIMS).

Smith says her team is busy with the groundwork to get to a point where non-expert users can trust that the near-real time images and information they get from the EO4WQ tool are accurate and useful.

“Once we know which algorithm works best, we can apply it to all of the historical satellite data as well. Many people involved in land-sea operations and coastal fisheries have indicated that they want to use this data, so we are making it available through EO4WQ in an accessible format for the first time.”

By December 2023, Smith hopes to have high resolution data on suspended sediments and chlorophyll levels available for anyone to access.

The EO4WQ prototype is currently hosted on the Cyanolakes website, which originally pioneered free satellite data on inland water bodies to the South African public.

Smith believes the public, including scientists, fishery operators, abalone farmers, journalists, municipal water managers, environmental managers, conservationists and others involved in the day-to-day coastal or estuary operations will benefit most from using this tool.

The EO4WQ project is a collaboration between the CSIR, Cyanolakes and OCIMS, and is funded by the South African National Space Agency (SANSA) through their NRF/NEOFronteirs programme.

#water quality #ocean colour #earth observation #oceanography

Satellite imagery can show real-time sewage spill impacts near Grassy Park

Zeekoevlei lake in Cape Town was closed to the public in 2021 due to sewage spills that caused large, harmful algal blooms. The lake is next to the Cape flats suburb of Grassy Park, and is a popular tourist attraction.

Water quality is in the spotlight currently as South Africa deals with poor waste water and sewage treatment, which may have led to cholera deaths in Gauteng, and water quality warnings in several other parts of the country.

LEFT: Sentinel 2 satellite image of Zeekoevlei lake in 2021. The lake was closed to the public due to sewage spills that caused harmful cyanobacteria to flourish into large algal blooms. RIGHT: Satellite imagery shows high levels of algal biomass (yellow). Processed through the Digital Earth Africa platform.

Dr Marié Smith, a CSIR expert on using satellite data to measure water quality, says easy-to-use satellite data is now freely available on the EO4WQ tool to help authorities and communities monitor coastal water quality in real-time.

"Zeekoevlei is an example of how we hope the EO4WQ tool might help municipalities to identify where water and sewage infrastructures may be lacking. As has happened in Tshwane with the Hammanskraal water quality crisis, local authorities might use satellite data to make a case for assistance to deal with serious or urgent water quality issues," says Smith.

She showed dramatic satellite images of South Africa’s coastal and estuary waters at the 2023 OCIMS stakeholder workshop, held in Cape Town on 22-24 May, 2023.

Smith’s team are further developing the “Earth Observation for Water Quality” (EO4WQ) tool, which will eventually become the official Water Quality Decision Support Tool for ocean governance, as part of South Africa’s National Oceans and Coastal Information Management System (OCIMS).

She announced that this year, her team will be adding powerful new capabilities to the tool, including high resolution imagery to show algal blooms at a resolution of 10m of the earth’s surface.

She demonstrated how authorities might use this to measure the impact of sewage spills on coastal water bodies like Zeekoevlei.

“Sewage contains nutrients, like nitrogen and phosphorus, that cyanobacteria use to grow and multiply. In the case of Zeekoevlei next to Grassy Park, these cyanobacterial blooms, also known as blue-green algal blooms, can be harmful to local ecosystems through excessive growth and the production of toxins,” says Smith.

In 2021, GroundUp reported that Zeekoevlei and several other water bodies in Cape Town had to be closed due to sewage spills, which also impacted water sports businesses, clubs and tourism.

Before Smith’s team began building the EO4WQ tool, satellite images for estuarine lakes and coastal water bodies were only available to experts and scientists who had the technical knowledge and resources to process large satellite data files. Now operators, authorities, conservationists and communities will have free access to simpler formats that can help with early warnings and disaster mitigation, and to identify where water infrastructures need to be improved.

The EO4WQ prototype is currently hosted on the Cyanolakes website, which originally pioneered providing satellite data on inland water bodies to the South African public.

Smith said they are working on adding time-series information and map-based information to show the amount of algae (algal biomass index), how clear the water is (turbidity index), true colour images of water bodies, and how much water there is (surface water extent).

EO4WQ will allow users to view data as a time-series. This image shows nutrient pollution that can lead to dangerous algal blooms over time in Durban, KwaZulu Natal.

Besides algal blooms, users can also look at South Africa’s coast from above to see striking red tides, shocking sand dredging damage, and clear upwellings from cold waters.

She says there are many other potential uses of the tool to monitor coastal water quality in real-time, so she invited potential users in its development by joining the Technical Advisory Group or to “simply give us your wish-list!”

EO4WQ will be able to give users daily updates in lower spatial resolutions for near-real time tracking, using data from the Copernicus Sentinel-3 satellite. But it will also provide incredibly detailed (but less frequent) images taken by the Copernicus Sentinel-2’s sensors to better understand historical changes in smaller water bodies like estuaries.

EO4WQ is a collaboration between the CSIR, Cyanolakes and OCIMS, and is funded by the South African National Space Agency (SANSA) through their NRF/NEOFronteirs programme.

#OCIMS #remote sensing #water quality #cholera #Hammanskraal #harmful algal blooms #sewage spill #grassy park #zeekoevlei #satellite imagery

Can South Africa use satellites to track how the construction industry is destroying coastal rivers and estuaries?

“Almost every river in KwaZulu Natal is being mined for sand, and much of that mining is illegal. The consequences are dire.”

This is according to Prof. Anthony Turton, a water resource expert based at Centre for Environmental Management, University of the Free State.

Removing thousands of tons of sand from free-flowing rivers increases the risk of devastating flooding disasters, and damages sensitive estuary and coastal ecosystems that support food production.

Sand mining also results in less sediment reaching the coast, and thus threatens our beaches and foredunes. This ultimately leads to a loss of coastal protection and increased vulnerability to coastal storms.

Turton and others have reported on illegal sand mining in KZN for some years, but it is difficult to monitor this criminal activity, and to fully grasp its impact, from the ground.

From space however, the picture of destruction is much clearer, especially over time.

Dr Lara van Niekerk, a principal estuary researcher at the CSIR, says that high resolution satellite data would make it easier to identify and track sand mining impacts. So a tool that could make such imagery accessible would be invaluable. “If we could demonstrate how the tool works and what its limits are, we could take this to the Department of Fisheries, Forestry and Environment and our provincial coastal management agency to detect impacts before that becomes significant ,” she says.

The Copernicus Sentinel-2’s satellite takes incredibly detailed images of the earth’s surface, which can be used to better understand historical changes in estuaries. But according to Dr Marié Smith, researchers, authorities and industries working in South Africa’s coastal and estuarine environments have struggled to use it.

“Raw satellite data files are often hard to find, and perhaps even harder to interpret. The huge files also don’t fit on regular laptops or desktop computers, and it is expensive to process the files into usable formats,” she says.

Smith is an expert in marine Earth observation at the CSIR, and leads a project called “Earth Observation for Water Quality” (EO4WQ).

“We’re working with some of South Africa’s top experts to turn raw satellite files into images, graphs and concrete numbers, to make it free and easy for operators, authorities and conservationists to monitor activities that could lead to disasters or declining water quality in coastal waters and estuaries,” she says.

The EO4WQ platform features a parameter called "enhanced vegetation", which shows Chlorophyll-a signals emitted by plants, for instance those growing around rivers and estuaries. Essentially it enhances the greens of plant matter on land and in the water.

Since sand mining erodes earth and damages vegetation in regular shapes, locating areas where vegetation is replaced over time by exposed brown earth due to sand mining should be possible with the EO4WQ platform.

The tool also features data from the Copernicus Sentinel-3 satellite, which could allow for near-real time tracking of such changes, albeit in lower spatial resolutions. Smith is calling on municipal operators to test the tool so that they can assess whether or not it would be useful to map and track sand mining activities to mitigate further environmental harm.

Turton, who is not involved in the EO4WQ project, says a good place to look would be the Umzimkulu River, most notably the lower reach from St. Helen’s Rock to the estuary. “This river was identified by the Department of Water and Sanitation as one of high ecological importance, yet illegal sand mining has fundamentally altered the bed, bank and flow in direct contravention of Section 21 of the National Water Act.”

[IMAGE: Here are two different satellite images of known legal sand mining sites on the Umzimkulu River in KZN: The “aerial photograph” was created using Google Maps, and the other using the “enhanced vegetation” option on the free EO4WQ tool. By using the near-real time EO4WQ tool to monitor specific hotspots where illegal mining is known to take place regularly, operators could spot new sand mining activity as quickly as one day from the operation starting. Operators can also rule out similar looking operations such as farm plowing by focusing on known hotspots. Credit: ScienceLink/EO4WQ]

Van Niekerk says the uMvoti river mouth in KZN is also known to be severely damaged by sand mining. In 2021, local media reported that the construction industry views uMvoti river sand as “gold”, and that illegal operators were freely excavating sand from the depleted banks in areas the municipality considers out of bounds.

EO4WQ prototype’s “enhanced vegetation” parameter could be used to produce images of vegetation loss at the Umzimkulu Marina near St. Helen’s Rock, as well as disturbances in vegetation over time near the UMmvoti river mouth, as long as a user knows what they’re looking for.

The “enhanced vegetation” index available on the EO4WQ platform shows information beyond the visible spectrum, so it compliments satellite images that focus only on true colour composites, such as those available on Google Maps or Google Earth. Often, imagery available on these platforms are also outdated, whereas EO4WQ receives updated satellite data every day.

[IMAGE: Here we show a section of the Umvoti river over 6 months (Sept. 2022 to February 2023. The first image is a static screenshot from Google Maps, showing riverbed sand available from above. The enhanced vegetation images were created using the free EO4WQ tool, and shows how river flow is interrupted and changes over time. Is it possible that sand mining contributes to these drastic changes and damages the river beds? We are calling on experts and authorities to test how useful the EO4WQ platform may be in monitoring estuary impacts due to legal and illegal sand mining. Credit: ScienceLink/EO4WQ]

Water resource experts and municipal operators likely have the knowledge about the situation on the ground to best use the EO4WQ tool to monitor the impact of sand excavations on water quality.

Indeed, satellite imagery has become an indispensable tool to monitor environmental crimes and activities like sand mining that threaten human communities the world over.

Smith and her team hope that EO4WQ’s will make this indispensable tool more accessible to South African authorities responsible for monitoring sand mining activity and enforcing compliance, as well as those responsible for dealing with the impact of sand mining on rivers.

Since the tool is still in development, she says it is important for potential users to test the tool and to provide feedback, so that the research team can establish the limits and value of the tool for tracking sand mining along South Africa’s coast, as well as other environmental uses.

EO4WQ is a collaboration between the CSIR, Cyanolakes and OCIMS, and is funded by the South African National Space Agency (SANSA) through their NRF/NEOFronteirs programme.

Watching our waters from space: SA’s first coastal water quality tracking app

Satellite images make it simpler and cheaper to track oil slicks, toxic algal blooms, floating plants and even rising sea surface temperatures.

Although such useful imagery already exists, researchers, authorities and industries working in South Africa’s coastal and estuarine environments have struggled to use it, says Dr Marié Smith.

Smith is an expert in marine Earth observation at the CSIR, and leads a project called “Earth Observation for Water Quality” (EO4WQ).

She says that for non-experts, raw satellite data files are often hard to find, and perhaps even harder to interpret. The huge files also don’t fit on regular laptops or desktop computers, and it is expensive to process the files into usable formats, such as a crisp picture or a graph showing changes over time.

“That is why we are building the EO4WQ tool. We want to, for the first time, make it free and easy to monitor historical or near real-time changes in coastal and estuarine water quality, using high-resolution data from the world’s best Earth observation satellites,” says Smith.

She is working with some of South Africa’s top experts to turn raw satellite files into images, graphs and concrete numbers. Such useful formats could, for instance, give early warnings to operators, authorities and conservationists to help prevent or mitigate disasters.

As an example, in 2017, a toxic algal bloom killed millions of abalone in Walker Bay, Western Cape. The animation above shows a similar situation in January and February of 2019 near Hermanus, Western Cape, where marine algae numbers got so out of hand that the toxins they produced caused a harmful “red tide” throughout nearby bays.

The animation was generated using satellite data. “Had operators seen such imagery indicating that a harmful bloom was about to be pumped into their aquaculture enclosures," says Smith, "they could have temporarily closed their inlets, changed filters and adjusted feeding schedules to preserve the water quality for their animals.”

A prototype of the EO4WQ tool that shows changing levels of chlorophyll, the bright green pigment characteristic of all phytoplankton, including harmful algal blooms, is already online. “I would encourage aquaculture farmers and the rest of the South African water quality community to explore the EO4WQ prototype as it's being built, because we welcome feedback to make it as useful as possible.”

Indeed, many others in the water quality community have already indicated that monitoring algal blooms is a top priority, but Smith says this is just one of the ways the tool could benefit coastal operations.

“Satellite data can also tell us about invasive floating plants that threaten native vegetation or fish; suspended sediments related to floods; water clarity for recreation; surface oil slicks from accidental spills, and even rising sea surface temperatures that could threaten sensitive ecosystems,” says Smith.

As they build the tool over the next 14 months, they hope to demonstrate how easily-accessible information from satellites can support efforts on the ground for each of these issues, and more as other applications come to light.

Smith says some users may appreciate daily updates in lower spatial resolutions for near-real time tracking, which they will obtain from the Copernicus Sentinel-3 satellite. Others might prefer incredibly detailed (but less frequent) images taken by the Copernicus Sentinel-2’s sensors to better understand historical changes in smaller water bodies like estuaries.

“In this early phase of our project, we are still calling on the public, including scientists, fishery operators, abalone farmers, journalists, municipal water managers, environmental managers, conservationists and others involved in the day-to-day coastal or estuary operations to let us know how else this tool could help them make decisions, so that we can build it in a way that is most useful to our community.”

She cautions that while satellite data can tell us a lot about the surface conditions like a green colour (from algae) or infrared radiation (from heat), it can’t tell us what’s going on under the surface, and it can’t measure things that don’t have visual or infrared tell-tale signs.

“Satellites also can’t capture clear images at night or through clouds, and they can’t give us specific information about pollutants or nutrients that might be dissolved in water,” says Smith.

EO4WQ is a collaboration between the CSIR, Cyanolakes and OCIMS, and is funded by the South African National Space Agency (SANSA) through their NRF/NEOFronteirs programme.

#satellites #earth observation #remote sensing #algal bloom #water quality #abalone #csir #space #south africa #science #research

We are building an online tool to help track coastal harmful algal blooms, sea surface temperatures, invasive water plants and oil spills in South Africa’s coasts and estuaries. The EO4WQ tool will make it free and easy for researchers, marine farmers, fishery managers, environmental watchdogs and local authorities to monitor historical or near real-time changes in water quality, using detailed imagery from the world’s best Earth observation satelites.

Project lead Dr Marié Smith, an expert in marine Earth observation at the CSIR, hopes that by making this satellite data accessible to the public for the first time, we can improve scientific research, disaster management, boost conservation and clean up efforts, and help oyster, abalone, crayfish and fishery industries thrive in our precious estuaries and coastal waters.

EO4WQ is a collaboration between the Coastal Systems and Earth Observation Research Group of the CSIR, CyanoLakes and the SANSA/NRF’s NEOFrontiers programme. The project will also contribute to the National Oceans and Coastal Information Management System (OCIMS).

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The recording of our 1st virtual stakeholder workshop, which took place on 15 June 2022

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Join us for our first online stakeholder workshop on 15 June 2022 at 10:00 SAST. Registrations are open at https://bit.ly/3LYPo0l

#Sentinel2 #Sentinel3 #water quality #remote sensing #earth observation #CSIR #OCIMS #NRF #SANSA #NEOFrontiers #satellites #ocean colour #coastal waters #estuaries

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