Instrumentation Monthly Test | Measurement | Control
The Norfolk Rivers Trust has installed a remote river monitoring station that has been tracking water quality and flow before and after river restoration work at an area of ecological importance on the River Nar.
In line with the requirements of the Water Framework Directive, the project is designed to ensure that the Nar maintains good ecological status by 2015 and in doing so it aims to improve the habitat for wildlife and promote biodiversity. The river monitoring station incorporates an Adcon GPRS telemetry unit from OTT Hydrometry, which automatically collects data and feeds a website.
Agricultural runoff is a particular problem in the Anglian region and many Norfolk Rivers contain high levels of nitrate and phosphate. Excessive levels of these nutrients can lead to eutrophication, symptoms of this can include vigorous growth of blanket weed; this change in water quality lowers dissolved oxygen levels in the streams and rivers, and harms wildlife.
Furthermore, in the past the Nar channel has been made straighter, wider and deeper; initially to improve navigation, and later to improve drainage. However, this has had a detrimental effect on wildlife. The River Nar also suffers from sediment deposition which has affected species that rely on gravel beds – such as brown trout which need sediment free gravel to lay their eggs.
The project
Assisted by funds from WWF-UK, the Coca-Cola Partnership and the Catchment Restoration Fund, the Norfolk Rivers Trust has established a £609k river and flood plain restoration project to reduce pollution in the River Nar and improve the habitat for wildlife.
The project began in June 2012 but prior to its commencement the Norfolk Rivers Trust measured water quality by collecting weekly samples and transferring them to their laboratory for analysis. This was a time-consuming and expensive activity and only produced spot data for the moment that a sample was taken.
In order to establish a continuous monitoring station for water quality and flow, OTT Hydrometry provided a Hydrolab Minisonde water quality monitor and an Adcon A755 Remote Telemetry Unit (RTU). In combination with a bed mounted Doppler flow meter (provided by the Environment Agency), the station is able to provide a continuous record of the river’s condition.
The Hydrolab Minisonde five takes measurements for turbidity, flow, conductivity, temperature and luminescent dissolved oxygen (LDO) every 15 minutes. The collected flow and water chemistry data is then stored and transmitted every hour via the RTU to an online server hosted by OTT Hydrometry. This allows information to be downloaded and analysed in the Trust’s office without the need for regular site visits. Data can be accessed at anytime from anywhere using the Adcon app.
Operating on extremely low power, and designed specifically for the collection and transmission of remote monitoring data, ADCON RTUs are able to utilise a variety of communication methods depending on site conditions.
The monitoring site on the Nar has some GSM coverage, but the signal is poor, so an ADCON A755 RTU was chosen to communicate via GPRS. This has been developed specifically for areas with low signal, because it stores all monitoring data when signal strength is too low for transmission, and then sends the information when signal coverage improves, sending the backed up data first.
Project officer Helen Mandley says: “To be able to judge the success of the project it is essential that we are able to compare water quality data from the old river channel to the new river channel, because we need to improve water quality in order to improve the biodiversity of the river.”
The results
In addition to water quality and flow monitoring, ecological assessments have been undertaken for water voles and other small mammals, macrophytes, aquatic invertebrates, vegetation and fish. However, before a reliable assessment of the project’s success can be undertaken, it will be necessary to evaluate data over an extended period so that seasonal effects can be taken into consideration.
Pre- and post-restoration data on ecology, water quality and flow will be assessed in September 2013, and it is hoped that this will provide clear evidence that the project has had a significant effect on water quality and biodiversity.
The current phase of the project is due to run until the end of 2013, but a series of ‘restoration units’ have been identified by The River Nar Steering group that includes the Norfolk Rivers Trust, each applying restorative work to a specific section of the river. These units extend to 2027 but will be reliant on the availability of future funding.
