Remote monitors track river restoration success

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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 the village of Tittleshall, the river flows south for 2.5 km until it reaches Mileham, then predominately west for 39.5 km through the villages of 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 consists of 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 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, providing easy access for the project team.

The Problem
Agricultural runoff is a particular problem in the Anglian region because of the light sandy soils which 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, 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.

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 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. For example, brown trout need sediment free gravel to lay their eggs.

The River Nar 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 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 2012. The project also includes the creation of reed beds and other in-ditch options to trap sediment before it enters the River Nar. Currently four reed beds have been installed in different areas in the River Nar catchment which also includes the dredging of an existing pond.

Monitoring
Prior to the commencement of the project, 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. 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.

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 5 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. For example, 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 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.

The monitoring equipment was installed at the end of July 2012 and restoration work began on 8th October 2012. Emphasising the importance of monitoring before and after the restoration work, 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.”

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.

Helen hopes to continue the project beyond 2013 commenting, “We currently monitor downstream of one of the new reed beds, but in the future we would like to place more monitoring equipment upstream of the reed bed to really see the differences, particularly in levels of turbidity and conductivity.”

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.

Clearly, environmental monitoring is essential for the evaluation and ongoing management of remediation projects, and OTT’s UK Managing Director Simon Wills says: “This project is a good example of how simple and low-cost it can now be to create a monitoring station that is sufficiently flexible to collect and transmit data from a variety of monitors.

“Advances in sensor, datalogging, communications and power management technology have combined to dramatically improve the effectiveness of remote data collection, which means that less site visits are necessary; thereby saving a great deal of time and money that can be spent on restoration.”

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