Feb 28 2022

Water Quality Monitoring – New for 2022

Anew set of water monitoring equipment has been installed to record the quality of water in the river and streams at Fingle Woods. This new system follows on from an initial scheme which provided a blend of good data and some learning experiences, with some technological hurdles negotiated. Lessons learned from that stage ensured that monitoring methods would be revised and equipment improved. The old monitoring system was based around a set of probes that sat in cages in the stream or riverbed. These would measure water pH at 7 locations and recorded water turbidity in a few of those places. Due to a lot of skill from Westcountry Rivers Trust (WRT) and dedicated work from Fingle volunteers (including resident electronics expert, Martin Beney) they provided a long-term view of water quality and started to map the effects of woodland management on the aquatic ecosystem. Their report also noted the need for some technical improvements, saying that the old probes were, “showing signs of instrumental drift and sporadic readings that we believe are due to old age.”


A new Aqua Troll 600                                                                           Old pH probe in a metal cage

Based on the initial work and experiences, the new set of sensing instrumentation is now being deployed on a shorter section of the catchment, between Fingle and Clifford bridges, but the probes will provide more accurate data across a broader range of factors or attributes. The manufacturer’s technical information says that “The Aqua TROLL 600 is a fully customizable multiparameter sonde with interchangeable sensors, long-lasting battery power, and a smartphone interface that delivers accurate data and enables simplified calibration, panoramic data view, and report creation. Ideal for short-term and long-term deployment.” In case you were wondering, a ‘sonde’ can be defined as an instrument probe that measures and transmits information about its surroundings from a remote location, such as underground or underwater.

As the new system was being installed, the WRT team members worked together to set up each ‘Troll’ and fix it in position at the edge of the flowing water. With the calibration underway, Holly was cleaning each sensor and immersing it in reference solution, a solution of known pH value. Ian was using a Bluetooth connected smartphone to set the readings at the right level before installation.

Simon explained that the acidity of water was just one of the parameters being measured. “This sonde will also indicate the level of pollution in the water by measuring conductivity. This is what we call the ‘total dissolved solids’ or the mineral content or sediment in the water in the stream”. Some of these particles may be naturally occurring, but can also be introduced by activities further upstream, including forestry work.


Installing the sonde in an upright tube                                           Calibrating the sonde

Calibration takes time and concentration but, once they were happy with the setup of the sensors, they were installed in an upright position. The new monitoring kit is providing a new start, so the redundant sensors and steel cages will now be recycled. This configuration is going to be more accessible to the monitoring team and should provide more reliable data; the sensor stays in the water and they don’t move about in the riverbed. Describing the new system, Holly explained that “There will be fewer probes, but they will measure more stuff. It’s a more compact survey and the downstream sensor locations will be moved up from Cod Wood to Clifford Bridge”

As the team split up and moved to different parts of the catchment, Simon and Ian continued to install the Troll sensors along the streams. Holly and Lydia gathered their tools, picked up a different set of sensors and moved on to Rivermead, the meadow just above Clifford Bridge. This is a part of Fingle where potential for habitat improvements includes the restoration of a floodplain meadow. It was planted with birch, willow and alder over 25 years ago but the beneficial effects on the ecosystems could be further improved if temporary flooding was encouraged with a Natural Flood Management (NFM) scheme. While they propelled their auger into the ground, they explained, “We are setting up soil moisture meters here, they are in a line across the meadow and will show us a profile of the soil moisture in the floodplain. They will work even if the meadow becomes flooded, once the water has receded, they will be accessible again. They are quite nifty”, Holly added.

Holly and Lydia using an auger to install soil moisture sensors in soil

There will be three more of these soil moisture probes by the existing NFM in Halls Cleave to show if the groundwater levels are changing next to the dams. This is another addition to the previous survey in response to the Westcountry Rivers Trust report that stated, “Soil moisture probes placed at given distances from a dam can give information on how effective the surrounding soils are able to absorb water as it backs up and spreads out into the flood plain behind a dam.”

This blog is written in memory of Martin Beney – his bench overlooks Halls Cleave where he spent many hours working as a skilled volunteer on the water monitoring system

by Matt Parkins


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