Smart Water monitoring demonstration in River Lee
A water quality monitoring project undertaken on the River Lee in Cork is a first for Ireland in understanding the aquatic environment and helping to protect resources, says Professor Fiona Regan of Dublin City University
Monitoring for the Water Framework Directive (WFD) at river basin level is a significant financial burden using conventional sampling and laboratory-based techniques. It is unlikely, however, that traditional spot/grab sampling provides the required reasonable estimate of the true maximum and/or mean concentration for a particular physico-chemical variables in a water body with marked temporal variability.
The DEPLOY project was an 18-month research and demonstration project that was co-funded by the Environmental Protection Agency (EPA) and the Marine Institute (MI). Its primary objective to implement a wireless sensor network of water quality monitoring stations. In doing so the aim was to demonstrate how this technology could operate continuously, remain robust, and provide an insight into processes involved and how this could better inform decision making for the relevant management agencies.
Recently the project report was published by the EPA and it highlights the project development, progress and recommendations. DEPLOY shows how state of the art technology can be implemented to achieve, continuous, real-time monitoring of a river catchment. It also represents an important collaboration among research centres, the National Centre for Sensor Research at Dublin City University, and the Tyndall National Institute (TNI), commercial partner Intelligent Data Systems and South Western River Basin District (SWRBD). (Table 1)
This technology demonstration of a truly heterogeneous water quality monitoring networked system is one of the first of its kind in Ireland. It shows how data can be collected from a number of locations and viewed in real or near real-time. The demonstration sites chosen are on the River Lee, which flows through Ireland’s second largest city, Cork. These were designed to include monitoring stations in five zones of the river considered typical of significant river systems and to demonstrate the versatility of the technology available. Each monitoring station collected data at pre-programmed intervals. Data was transmitted to the DEPLOY servers either by short range ISM band radio or directly via the GSM GPRS network. The data was then processed and made available in a controlled manner to end users over the internet network.
The technology demonstration involved the integration of a group of freely available commercial water quality and environmental sensors into a distributed communication network to demonstrate how real-time data acquisition can be implemented. In selecting the instruments implemented in the DEPLOY project, the partners considered the project requirements including:
- The selection of typical parameters that are commonly measured by regulatory agencies including conductivity, pH, temperature, dissolved oxygen (DO), turbidity and chlorophyll-a (chl-a)
- The need for deployment of the instruments for one year, which meant it was important to select sensors that were from reputable suppliers
- The instrument budget needed to cover the five sites chosen by the project team
The River Lee is one of the largest rivers in South-west Ireland, with a total catchment area covering approximately 1,250km2. The river rises in the Shehy Mountains near Gougane Barra, to the west of Cork, and flows in an easterly direction before reaching Cork harbour some 85km away. From its upland source, the river flows through countryside alternating between areas of moorland and small farms before reaching the two reservoirs at Carrigadrohid and Inniscarra, created in the 1950s after the erection of two hydroelectric dams. These elongated reservoirs stretch for some 26km and have a storage capacity of 45Mm3, with the Inniscarra reservoir located approximately 13km west of Cork city.
The monitoring sites chosen by the DEPLOY project are near the source, in a reservoir, in the main channel of the river, adjacent to joining tributaries and finally, in the estuary, which is tidal and partially saline. Tidal influences in the River Lee provide interesting physico-chemical data that show temporal changes in water quality. Variations in these regular parameters can indicate anthropogenic influences in the riverine system. The sites on the River Lee extended from the Gougane Barra to the Lee Maltings in Cork City.
The implementation of the sensor network deployed provides three key advantages over traditional water quality monitoring mechanisms:
- Demonstration of benefits of high temporal resolution data
- Provision of data from multiple sensors from multiple sites in the catchment
- Provision of data in real-time to the user
The ability of the DEPLOY project to remotely monitor temporal and spatial variations in environmental water quality can provide more up-to-date information This could potentially cut overall monitoring costs and provide better coverage representing long-term trends in fluctuations of pollutant concentrations, thus demonstrating the potential for adoption of water monitoring technology as part of a monitoring programme in Ireland.
Almost two million data points were collected at the indicated resolution and granularity. This required the development of new data handling and analysis methods. As a result, the project partners can make significant recommendations for water quality monitoring systems from various perspectives, technical, operational and strategic. This data consisted of high temporal frequency (usually every 10 minutes), but not all parameters were measured at all sites.
The water quality data was plotted in real time and viewed on the website. It was possible to overlay parameters for each site, compare parameters form different sites and vary the timeframe over which parameters are viewed. A monitoring system of this nature can provide real-time data on a variety of water quality parameters over long periods of time, allowing researchers and policymakers to advance their understanding and protect resources.
From the 12-month deployment it was possible to observe:
- Data quality changes and the reasons for changes
- How site-specific conditions affect the data collected
- That there is real value in collecting data every 15 minutes
- That there is a requirement to maintain and clean sensors frequently to maintain data quality
- That depending on the season and location, data quality may change due to bio-fouling
- How data can be presented online to suit any user’s need, and that it is for the user to decide how they want to present the data
It is widely recognized that it is necessary to carry out regular maintenance on sensors deployed in the aquatic environment. Routine maintenance frequency is generally governed by the fouling rate of the sensors.
This rate varies widely depending on location, sensor type, hydrologic environment, and season. Biofouling is the principal limiting factor affecting the operation, maintenance and data quality of long-term in situ water sensor monitoring. Biofouling limits the effective deployment period of water quality sensors.
It diminishes their performance by isolating sensors from the measuring environment and possibly creating microenvironments that alter the chemical concentrations of the parameters of interest (Johnson et al., 2007; Delauney et al., 2010).
The performance of temperature, pH and conductivity sensors tends to be less affected by fouling, whereas the optical DO, chl-a and turbidity sensors are more prone to fouling. In order to ensure data quality, maintenance visits that involved sensor cleaning were carried out at each station every two weeks.
This was necessary during the summer months and less so during autumn and winter
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