Keep on tracking
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
Rising in chalk hills to the east of of Tittleshall, the River Nar flows south for 2.5km until it reaches Mileham, then predominately west for 39.5km through Litcham, Castle Acre, West Acre and Narborough until it reaches the tidal Ouse at King’s Lynn. The river rises on chalk and in its course to Narborough flows over chalk formations.
In its lower course the underlying geology is more complex and comprises a progression from Narborough downstream through a series of clays and greensands, making it one of only a few remaining fenland chalk streams.
In line with the requirements of the Water Framework Directive, the Norfolk Rivers Trust (NRT) has established a remote river monitoring station to track the river’s water quality and flow. 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 that automatically collects data and feeds a website, providing easy access for the project team.
Agricultural run-off is a particular problem in the Anglian region because of the light sandy soils that are easily eroded during times of heavy rainfall. Fertilisers can add to the problem because they can be washed from the field and end up in water courses.
As a result, many Norfolk rivers contain high levels of nitrate and phosphate. Excessive levels of these nutrients can lead to eutrophication. In the past, the Nar channel has been made straighter, wider and deeper to improve navigation and drainage. However, this has had a detrimental effect on wildlife.
The Nar also suffers from sediment deposition arising from point sources such as land drains, and from diffuse sources such as run-off resulting from cultivation in wet periods. This has affected species that rely on gravel beds for any stage in their lifecycle.
Assisted by funds from WWF-UK, the Coca-Cola Partnership and the Catchment Restoration Fund, the NRT has established a £609,000 river and flood plain restoration project to reduce pollution in the Nar and improve the habitat for wildlife.
The project began in June 2012 and includes work to change the course of the river from a straight incised channel to a meandering route, reconnecting the river to the floodplain, which would create new habitats.
This channel restoration project was completed in October. The project also includes the creation of reedbeds and other in-ditch options to trap sediment before it enters the Nar. Four reedbeds have been installed in different areas in the River Nar catchment, which also includes the dredging of an existing pond.
Prior to the commencement of the project, the NRT measured water quality by collecting weekly samples and transferring them to its laboratory for analysis. This was a time-consuming and expensive activity and only produced spot data for the moment that a sample was taken.
Consequently, events that took place at night or between the sampling interval were not detected, so there were clear advantages to be obtained from continuous monitoring.
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 can provide a continuous record of the river’s condition.
The Hydrolab Minisonde 5 measures 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, allowing 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.
ADCON RTUs can utilise a variety of communication methods depending on site conditions. Radio represents a low-cost alternative in areas with poor GSM coverage and where line of sight is possible, with repeaters if necessary.
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. The A755 RTU was 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.”
Pre- and post-restoration data on ecology, water quality and flow will be assessed this September, and it is hoped that this will provide clear evidence that the project has had a significant effect on water quality and biodiversity.
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