Tamar management catchment: baseline length of rivers and estuaries polluted by abandoned metal mines
Published 12 March 2025
Applies to England
© Crown copyright 2025
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This publication is available at https://www.gov.uk/government/publications/abandoned-metal-mines-in-england-baseline-length-of-rivers-and-estuaries-polluted-by-harmful-metals/tamar-management-catchment-baseline-length-of-rivers-and-estuaries-polluted-by-abandoned-metal-mines
This is one of 20 reports, one for each polluted management catchment, on the water quality monitoring undertaken by the Environment Agency to determine the baseline length of rivers and estuaries considered polluted by any of the Environment Act target substances from abandoned metal mines in 2022.
A length of river or estuary is considered polluted where the concentration of one or more of the 6 target substances (arsenic, cadmium, copper, lead, nickel and zinc) exceeds the relevant Environmental Quality Standard (EQS). EQS concentrations are based on ecotoxicology data and set by government at a level that should prevent harmful environmental impacts. When the concentration of a substance in a water sample is higher than the EQS, adverse impacts on the aquatic ecosystem can be expected. The relevant EQS for each target substance are set out in The Water Framework Directive (Standards and Classification) Directions (England and Wales) 2015.
The purpose of calculating this baseline was to enable measurement of the statutory abandoned metal mines target set out in Part 4 of the Environmental Targets (Water) (England) Regulations 2023. This regulation requires that the combined length of English rivers and estuaries polluted by the target substances from abandoned metal mines is, by 31 December 2038, at least 50% lower than the baseline.
In the Tamar management catchment, the baseline length of polluted rivers for the abandoned metal mines water target is 90km. We will aim to identify the key sources of metal pollution in this management catchment by carrying out detailed monitoring investigations.
You can find further background and context on the Environment Act abandoned metal mines water target in the national baseline report which should be read together with this report.
The Tamar management catchment
The Tamar management catchment covers an area of approximately 1,820km2 and includes the western extent of Dartmoor National Park, the Tamar Valley National Landscape, South Devon National Landscape and Cornwall National Landscape. Please go to Tamar Management Catchment on the Catchment Data Explorer for an interactive map showing the 7 operational catchments that make up the management catchment. The boundary of the Tamar management catchment and all 7 operational catchments are highlighted in Figure 1.
Metal mining in the Tamar management catchment
Within the Tamar catchment, there has been evidence of metal mining since before Roman times. Mining in the region expanded from the 12th century onwards, initially with tin and then lead and silver. During the 18th and 19th centuries, mining boomed in the Tamar valley, with the discovery of substantial copper lodes, while arsenic was also produced during the second half of the 19th century. Great Devon Consols, in the Lower Tamar, was a particularly large producer of copper and arsenic. Manganese and tungsten were also mined in the region, albeit in smaller quantities. However, from the late 19th century onwards, many mines closed, with Great Devon Consols closing in 1903, and mining declined within the area, leaving behind a legacy of pollution (visit Mining Heritage in the Tamar Valley for more information). Some tungsten mining continued at Hemerdon mine until 1944. Between 2015 and 2018, the Hemerdon tungsten-tin mine operated before closure (for more information, visit Tungsten West).
Figure 1 shows the locations of mineral veins, known mine water discharges, closed mine waste facilities known to be causing serious environmental harm, and recorded areas of abandoned mine wastes (mining spoil) in the Tamar management catchment.
This information has been gathered from various sources including:
- BGS Geological mapping - GeoIndex - British Geological Survey
- Prioritisation of abandoned non-coal mine impacts on the environment
- Inventory of closed mining waste facilities causing serious environmental impacts
- Defra-funded ‘Source apportionment of pollution from non-coal mines’ research project by Newcastle University and Hull University (unpublished)
- Environment Agency water quality data archive
As we can see in Figure 1, mining mostly occurred towards the south of the Tamar management catchment, in the Tavy, Tamar Lower and Inny, and Lynher operational catchments.
Figure 1. Map showing the abandoned metal mines, mineral veins and baseline river monitoring sites in the Tamar management catchment
© Environment Agency
The tables below list the catchments (surface water bodies) that are polluted by target substances from abandoned metal mines in the Tamar management catchment. These tables highlight where there are known point sources (mine adits or mine drainage levels) and diffuse sources (mine wastes or spoil heaps) within the catchment. The Environment Agency is continuing to investigate point and diffuse sources within the Tamar management catchment by undertaking a series of catchment characterisation studies. These studies will help us identify which sources of metals need to be tackled to achieve the long-term statutory target.
Tavy operational catchment: sources of metal pollution
Table 1 summarises which type of pollution sources from abandoned metal mines have been identified within the catchments (surface water bodies) in the Tavy operational catchment.
Table 1: Summary of metal pollution sources within the Tavy operational catchment
| Catchment (Surface water body) | Point sources of pollution | Diffuse sources of pollution |
|---|---|---|
| Upper River Tavy | Yes | Yes |
| Burn (Tavy) | Further investigation required | Further investigation required |
Tamar Lower and Inny operational catchment: sources of metal pollution
Table 2 summarises which type of pollution sources from abandoned metal mines have been identified within the catchments (surface water bodies) in the Tamar Lower and Inny operational catchment.
Table 2: Summary of metal pollution sources within the Tamar Lower and Inny operational catchment
| Catchment (Surface water body) | Point sources of pollution | Diffuse sources of pollution |
|---|---|---|
| Lower River Tamar | Yes | Yes |
| Cotehele Stream | Yes | Yes |
Lynher operational catchment: sources of metal pollution
Table 3 summarises which type of pollution sources from abandoned metal mines have been identified within the catchments (surface water bodies) in the Lynher operational catchment.
Table 3: Summary of metal pollution sources within the Lynher operational catchment
| Catchment (Surface water body) | Point sources of pollution | Diffuse sources of pollution |
|---|---|---|
| Lower River Lynher | Yes | Yes |
Baseline monitoring
The objective of the baseline monitoring was to establish the upstream and downstream extent of surface waters polluted by the target substances from abandoned metal mines. We selected the baseline monitoring sites by first completing a desk study to review previous water quality data, maps and reports. We then made initial site visits to collect samples and to assess the suitability of the site for continued sampling. Generally, at least twelve water quality samples were then collected from each monitoring site.
Within the Tamar management catchment, water quality monitoring was undertaken in 3 of the 7 operational catchments, with these being the Tavy, Tamar Lower and Inny, and Lynher operational catchments. These catchments are shown in Figure 1. We did not carry out monitoring in operational catchments where there is either no historical metal mining within the catchment or a combination of current and historical monitoring data shows that waterbodies within these catchments are not polluted by abandoned metal mines.
In total, 73 monitoring sites were selected across the Tamar management catchment to determine the baseline length of rivers polluted by target substances from abandoned metal mines. The locations of these monitoring sites are shown in Figure 1.
Water quality data collected between 1 January 2022 and 31 March 2024 have been used to determine and validate the baseline length of rivers and estuaries considered polluted in 2022. The length of rivers polluted by abandoned metal mines fluctuates in response to natural variation in rainfall and river flows. However, this length will not materially change unless remediation measures like mine water treatment schemes or diffuse interventions are installed to decrease inputs of metals. Therefore, data collected after 31 December 2022 are considered to be representative of rivers, provided no new remediation measures had been constructed since 2022. No new remediation measures have been constructed in the Tamar management catchment since 2022.
Water quality monitoring results
In the Tamar management catchment, the target substances measured were cadmium, copper, lead, nickel and zinc. We did not undertake testing for arsenic in this management catchment since historical monitoring data showed that whilst there is elevated arsenic in some mine water discharges, no rivers are polluted by arsenic in this management catchment.
The baseline water quality data for all monitoring sites are available on the Environment Agency’s public water quality archive.
For a river water quality sample to be considered polluted, concentrations of one or more of the target substances must exceed the relevant EQS set by government when assessed as an “annual average”. The EQS are set out in The Water Framework Directive (Standards and Classification) Directions (England and Wales) 2015.
The EQS are derived using ecotoxicology data and set at a level that should prevent harmful environmental impacts. When the concentration of a substance in a water sample is higher than the EQS, adverse impacts on the aquatic ecosystem can occur, and the sample is considered to be polluted.
To understand the severity of pollution, we calculated a numeric “pollution level” by dividing the measured concentration of the target substances by the EQS. If the pollution level is greater than 1, the monitoring site is considered polluted by that target substance. Therefore, the higher the numeric pollution level, the greater the likelihood of harm to aquatic life.
Baseline polluted river length: Tamar management catchment
Our detailed monitoring across a range of flow conditions between January 2022 and March 2024 shows that in the Tamar management catchment, the baseline length of polluted rivers for the abandoned metal mines target is 90km.
Figure 2 shows the rivers in the Tamar management catchment that are polluted by target substances from abandoned metal mines.
Figure 2. The baseline length of rivers polluted by target substances from abandoned metal mines in the Tamar management catchment is 90km
© Environment Agency
Table 4 shows the river length (in km) that are polluted by each of the target substances within the Tamar management catchment. In general, the most polluted rivers are impacted by more than one target substance.
Table 4. River length (in km) polluted by each of the target substances within the Tamar management catchment.
| Target substance | Polluted river length (km) | Pollution level: less than 3 times | Pollution level: 3 to 5 times | Pollution level: greater than 5 times |
|---|---|---|---|---|
| Cadmium (Cd) | 62 | 28 | 14 | 20 |
| Lead (Pb) | 10 | 5 | 3 | 2 |
| Nickel (Ni) | 4 | 3 | 1 | 0 |
| Zinc (Zn) | 82 | 36 | 7 | 39 |
| Copper (Cu) | 67 | 40 | 7 | 20 |
Rivers polluted by abandoned metal mines: Tamar management catchment
Tavy operational catchment: baseline polluted rivers
The main River Tavy is not polluted by metals from abandoned metal mines. However, several tributaries of the River Tavy are polluted by metals. Cholwell Brook is polluted by copper, zinc, lead, and cadmium downstream of the former Wheal Betsy mine. The River Burn tributary is polluted by zinc and cadmium from downstream of the former West Friendship mine to the confluence with the Tavy.
Figure 3 shows the baseline polluted rivers in this operational catchment.
Figure 3. The baseline length of rivers polluted by target substances from abandoned metal mines in the Tavy operational catchment is 10km
© Environment Agency
Tamar Lower and Inny operational catchment: baseline polluted rivers
The lower River Tamar is not polluted by metals from abandoned metal mines.
There are however several tributaries that are polluted by the target substances within the catchment. The Luckett Stream is one such tributary, which is polluted with copper, zinc and cadmium across most of the waterbody. However, it is not polluted in its headwaters above Old Mill. Latchley Brook is polluted by copper at its downstream monitoring location. Portontown Stream is polluted by copper, zinc and cadmium in its lower reach before the confluence with the River Tamar. The Cotehele Stream is polluted by target substances throughout most of the catchment, with high copper concentrations present in the Harrowbarrow and Metherell Streams. However, the Burraton and St Dominick Streams are not polluted by metals from historical mining activities.
Figure 4 shows the baseline polluted rivers in this operational catchment.
Figure 4. The baseline length of rivers polluted by target substances from abandoned metal mines in the Tamar Lower and Inny operational catchment is 30km
© Environment Agency
Lynher operational catchment: baseline polluted rivers
The River Lynher is not polluted upstream of the Darleyford Stream tributary but is then polluted by copper and zinc until the tidal limit at Notter Mill.
The Darleyford Stream is polluted by copper, zinc, and cadmium throughout its length, with very high copper concentrations present around the former Phoenix Mine site at the top of the stream. The Marke Valley Stream is also polluted by copper throughout the waterbody, with additional failures for zinc and cadmium in the lower stretches of the stream. Copper, zinc, and cadmium pollute the Tokenbury Stream, except in the Penharget tributary. The Haye Valley Stream and its tributaries are also polluted by target substances, especially zinc and cadmium, with a discharge from Redmoor Mine being a major pollution source.
Figure 5 shows the baseline polluted rivers in this operational catchment.
Figure 5. The baseline length of rivers polluted by target substances from abandoned metal mines in the Lynher operational catchment is 50km
© Environment Agency