viii UK Focus - Water/Wastewater


A Network of High-Frequency Sensors Helps Protect the Future of Fresh Water Lakes


The Need for High Frequency Lake Monitoring Lakes across the world are often in areas of outstanding natural beauty, enriching the landscape and our lives with their serene environments. They also provide the highly important economic functions in the supply of water, food, energy, flood control, and recreation. Often, they also support a tourist industry with major local economic benefits; for example 15 million people sample the delights of the English Lake District each year.


Currently, for example, cyanobacterial blooms are widespread in many lakes around the world and since they are potentially toxic to livestock, pets and humans their occurrence severely restricts the use to which the lake and the lake water can be put.


During the early part of the 20th century, many lakes in Western Europe and elsewhere were affected by raw sewage and fertiliser run- off from agriculture, degrading the economic benefits they provided and causing severe ecological damage and loss of species. Subsequent improvements in waste water management and farming practises have started to reverse these effects, but rates of recovery are low and other environmental pressures such as those caused by climate change, invasion of non-native species, water abstraction and atmospheric deposition have added further pressures. Currently, for example, cyanobacterial blooms are widespread in many lakes around the world and since they are potentially toxic to livestock, pets and humans their occurrence severely restricts the use to which the lake and the lake water can be put.


High frequency data are needed to understand how the different environmental pressures affect lakes and to forecast future responses. This is because lake condition can change rapidly, since the generation time of the largely microbial populations that control ecological structure and function is very short, of the order of days or less. Equally importantly, lakes are strongly influenced by short-term weather events, such as a storm or a flood, or a period of hot weather.


The UKLEON (United Kingdom Lake Ecological Observatory Network http://www.ceh.ac.uk/sci_programmes/water/uk-lake-ecological- observatory-network.html) project has developed an innovative sensing system exploiting new technology in sensors, data-loggers, computing and telemetry to collect high frequency ecological data automatically from remote sites. This not only provides a huge advantage for scientific research, but also has the potential to provide environmental managers or water companies with up-to-date information.


Author Details:


Prof Stephen Maberly, Lake Ecosystems Group Centre for Ecology & Hydrology


Lancaster Environment Centre, Lancaster LA1 4AP Tel: 01524 595851 Email: scm@ceh.ac.uk


http://www.ceh.ac.uk/sci_pro- grammes/water/uk-lake-ecologi- cal-observatory-network.html


The Network and Monitoring System


A network of automatic water quality monitoring stations (AWQMS) has recently been deployed across eleven lakes in the UK, including sites in England (5), Scotland (3), Wales (2) and Northern Ireland (1). The sites cover a very large variety of lake types and sizes; ranging from unproductive to productive, small to large, shallow to deep and lowland to upland.


Each AWQMS is equipped with a meteorological station to record local weather. Underwater, there is a chain of platinum resistance thermometers measuring temperature at a range of depths. Sub-surface, several sondes measure temperature, conductivity, pH, carbon dioxide, underwater


IET September / October 2013 www.envirotech-online.com


The location of the eleven UKLEON monitoring stations. Organisations responsible for each station are shown in parentheses.


light and dissolved oxygen; the latter variable is measured using fluorescence which is much more reliable and stable than the electro-chemical technology used previously.


The concentrations of the biological pigments chorophyll a (the green pigment in all photosynthetic algae and plants) and phycocyanin (a blue pigment that is specific to cyanobacteria or blue-green algae) are also measured using fluorescence. In addition, a sensor designed to measure carbon dioxide in air has been modified by the addition of a water-proof but carbon dioxide-permeable membrane so that it measures carbon dioxide in water.


An automatic water quality monitoring station on Blelham Tarn.


Finally, there is an underwater light sensor to measure the light in water in comparison to a similar sensor just above the water surface. Bio-fouling of the sensors, especially in productive sites, has been largely overcome with automatic wipers to remove biofilm. Each AWQMS is powered by lead-acid batteries with most of the power in the summer provided by two solar panels.


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