A Light aircraft with special instrumentation and a camera pinned to its undercarriage looks set to be the new way of checking the environmental status of Irish lakes.
The technology enables up to 100 lakes to be monitored in a day. It was developed by Spectral Signatures, a campus company in UCD, and is proving to be a highly reliable method of assessing water quality, according to the Environmental Protection Agency.
Irish freshwater lakes are among the most important ecosystems in Europe. That, combined with their vulnerability to pollution, underlines the need for regular monitoring of their waters. A gradual but relentless decline in their quality means early warning systems are vital if there is any chance that they are going to retain their uniqueness, let alone their health. Taking samples that indicate the quality of such water systems is not just a matter of dipping a sample bottle below the surface. Many lakes - there are some 5,000 in all - are remote and inaccessible. Samples may be taken on some lakes only infrequently despite the best intentions of fisheries and environmental agencies.
In many instances lakes are subject to rapid change; most notoriously in the case of over-enrichment by phosphate wastes. Such conditions can lead to an algal bloom and change the toxicity of water in a matter of hours. The resulting damage may take years to rectify, if it can be repaired at all. Seasonal changes also need to be factored in, but often they are not because of the sheer scale of monitoring required.
The airborne lake monitoring system developed by Spectral Signatures quantifies the amount of algae in the water, and is a particularly exciting development in the quest to improve monitoring and introduce both effective catchment management and pollution control, according to EPA water scientist Mr Martin McGarrigle.
It was developed with the Central Fisheries Board in a project that was part of the most extensive series of studies on Irish lakes - a £1.3 million programme overseen by the EPA and supported by the EU.
A variety of aircraft, including helicopters, can be used. A portable hyperspectral spectrometer is mounted near the tail. This measures green colour coming from the photosynthetic cell component, chlorophyll, reflected from the lake. This in turn indicates the amount of algae present. The instrumentation can also identify key algal groups in the lake, including the blue-green variety, which can be an early indication of trouble, explained Dr Eoin O Mongain of Spectral Signatures.
The spectrometer processes the full spectrum of light reflected from the water. Absorption in the red region of the spectrum is most indicative of the chlorophyll contained in the algae. They can take hold from springtime, and their levels are determined by sunlight and nutrient levels in the lake.
Also mounted on the aircraft is a video camera. Its footage is fed into a computer which generates an enhanced image. This allows for the creation of lake maps, indicating shorelines, submerged vegetation and surrounding land-use patterns. The use of this remote sensing system is also reasonably economic, Dr O Mongain said. "For about £1,000, you can monitor all the lakes of Cavan and have data next day."
Of most significance is reliability. "We have demonstrated that an indigenous and locally based aerial remote-sensing capability can provide information with the accuracy, resolution and timeliness which is required for lake monitoring in Ireland."
Because of cloud cover factors and instrumentation constraints, the extent of data it provides is unlikely to be improved on by satellite-based systems for the foreseeable future, he said. Moreover, the UCD technology enables low-altitude monitoring using a robust and validated system. Weather not suitable for light aircraft is the only constraint.
The accuracy achieved by airborne monitoring of 500 Irish lakes - including small ones of less than two hectares - was better than traditional bottle sampling, while the system proved to be a reliable indicator of overall lake health.
