Remote sensing for water quality monitoring

June 26th, 2016, Published in Articles: PositionIT

 

Dr Mark Matthews June 2016 profile photo

Dr. Mark Matthews

On 23 June 2016 Dr. Mark Matthews demonstrated the Earth Observation National Eutrophication Monitoring Programme’s (EONEMP) at the Resource Quality Services of the Department of Water and Sanitation.

EONEMP is an online water quality monitoring system which uses satellite data to monitor algae and cyanobacteria levels for 102 dams in South Africa, to assist in aquatic ecosystems management. The results are visualised online in a dashboard, map and table format for a user friendly overview with easy filter and search options according to waterbody and risk level.

Cyanobacteria blooms, which colours the water blue-green, is a health risk especially in freshwater bodies, as it produces an array of toxins which affect the nervous system and liver, and can lead to deaths in humans and animals. These blooms are the result of eutrophication – a process whereby nutrients such as nitrates and phosphates (through fertilisers and waste water) enriches the water and increases the concentration of algae and cyanobacteria.

Cyanobacteria’s colour properties and its process of photosynthesis make it observable and measurable using multi-spectral satellite imagery. MERIS data was used in the current classification, and was verified against the Department of Water and Sanitation’s field-measurements in its National Eutrophication Monitoring Programme (NEMP).

The visualised information on a website gives an overview of the risk levels according to high, moderate, mild and low; further classifying water bodies as safe for fishing, swimming and drinking.

Since MERIS data from 2002 to 2012 was used, the system serves as a long-term historic catalogue, though there are plans to incorporate Sentinel 3 data in the near future, so as to provide real-time monitoring. The same algorithms can then be applied to the Sentinel data, as it uses the same type of Ocean and Land Colour Instrument (OLCI) as MERIS.

EONEMP dashboard overview of the risk levels for 102 dams in South Africa.

EONEMP dashboard overview of the risk levels for 102 dams in South Africa.

The current results, up to 2012, paint a dire picture, with 11% of water bodies posing immediate health risks, highlighting the need to reduced nutrients in the water, especially from waste water.

Satellite monitoring makes large area monitoring of water bodies possible, but only works for water bodies larger than 1 km2. The historical data could also lead to insights over time to indicate bloom patterns, while the real-time data would help focus treatment programmes.