A partnership between the Woodland Trust and the National Trust

Looking Deeper into the Water of the Teign

For those of us fortunate enough to walk along the banks of the River Teign in Fingle Woods, we can admire the beauty of the rippling water; clean and sparkling as it bustles along its tree lined channel. We can enjoy the sight and sound of the fresh water tumbling down the small gullies, carrying cool, clear water from the fields and forests above the gorge to join the river on its way downstream. The scene along the Teign is a visual treat where the pure, moist air and tumbling torrents can satisfy the senses but, how do we know what is actually in that water? Is it all as pure as we might think?

The dipper – a resident of the River Teign [photo: P. Moody]

Earlier this year, a team of experts was assembled to look into the water courses in the valley and find a way to study and record exactly what is going on. A combination of science and technology would be needed to get to the bouldery bottom of this question and produce some transparent results.

The Woodland Trust’s Dave Rickwood explained how “in the early stages of the woodland restoration, a group of local anglers suggested that monitoring the Teign could help us to understand the impact of water quality on the numbers of fish. We pursued this idea and the development of this new project will also provide us with some important information on the impact of the woodland restoration. If we monitor the water before, during and after woodland management work we hope to see whether our improvements to the woodland habitat will also benefit the quality of the water”.

In their initial report, the Westcountry Rivers Trust suggested that “little is known about the current effects of woodland management of this type on water quality, and the data from this project will be of interest to anglers, foresters and regulatory bodies alike”. But, to collect this data in a steep sided gorge would be a challenge. To provide a full set of information, a set of sensors has been installed in the tributaries and in two places, upstream and downstream along the Teign. Due to the precipitous terrain, real-time records of acidity and temperature will be sent via a telemetry system to a receiving post at Tim Cox’s farm above the valley. From there, the results can be monitored over the internet.

Stream sensor locations (blue), upstream and downstream river monitoring points (yellow) and relay stations (red)

There are also two new rainfall sensors, one on each side of the valley to provide “contextual evidence” for any changes in the water quality. In addition to all these sensors, a turbidity sensor was installed in the Halls Cleave stream, the largest of the five Teign tributaries. Turbidity is a measure of the optical clarity of the water. High turbidity can be an indication of pollution from excess sediments being discharged or disturbed in a water course which can smother the river bed, causing problems for spawning fish and invertebrate health. The first set of recordings will provide a baseline of data which can be compared with future readings during and after forestry operations.

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Much of this hi-tech equipment was installed by the National Trust volunteers. As well as their expertise in conservation and land management, the Teign Valley team has many other hidden talents. Martin Beney is an expert in electronics and has installed a lot of the remote sensing equipment and the telemetry stations around the surrounding landscape. As you walk along the riverside track you may see wooden boxes and aerials mounted on trees. These have been installed by him and other members of the team, using their tree climbing skills.

Michael installing the monitoring aerial [photo: M.Beney]

Even though this project is in its early stages it is showing some interesting results. The WRT explained “there were the diurnal swings in pH seen at all the monitoring sites, but excess CO2 in this case is produced by increased biological respiration during the night, as opposed to increased photosynthesis during the day which uses up CO2 to produce oxygen”

An example of the diurnal swings in pH logged at Butterdon Ball Wood Stream. The graph shows four full days (1st – 5th July 2017) of data logged every 15 minutes

As well as current human activities, past events are still playing their part. “A legacy of acid rain (pH < 5) resulting from increased industrialisation in western Europe as far back as 1860 is thought to still affect areas on Dartmoor. Historically, the technology used for reducing emissions of these pollutants was not as advanced as present and their persistent nature can still contribute to the acidification of water courses”.

So, there is still a long way to go before we get a clear picture of this part of the river catchment, but the undimmed enthusiasm of the Fingle Woods team will hopefully ensure a bright future for the waters of the Teign.

by Matt Parkins

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