Aire and Calder 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 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 Aire and Calder management catchment, the baseline length of polluted rivers for the abandoned metal mines water target is 2km. 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 Aire and Calder management catchment
The Aire and Calder management catchment covers an area of approximately 2,017km2. The catchment stretches from the southern edge of the Yorkshire Dales National Park through the upper Calder valley, down through the cities of Bradford, Leeds and Wakefield. Go to Aire and Calder 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 Aire and Calder management catchment and all 7 operational catchments are highlighted in Figure 1.
Metal mining in the Aire and Calder management catchment
There is evidence of lead mining in the Yorkshire Dales since pre-Roman times. The main area of interest is Cononley Beck which is located in the Aire Upper Catchment. The lead mine at Cononley was opened during the 1800s, closing in the late 1800s. The mine was then re-opened in the 1920s and 1930s and mined for the mineral barytes which were re-worked from the spoil heaps. For further information please visit Cononley Mine - Northern Mine Research Society.
Figure 1 shows the locations of mineral veins, known mine water discharges, closed mine waste facilities known to be causing serious environmental harm, and areas of abandoned mine wastes (mining spoil) in the Aire and Calder 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 from Figure 1, historical mining activities in the Aire and Calder management catchment were concentrated in the Aire Upper operational catchment in the area around Glusburn Moor approximately 1km to the south west of Cononley village.
Figure 1. Map showing the abandoned metal mines, mineral veins and baseline river monitoring sites in Aire and Calder 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 Aire and Calder 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 waterbody catchment. The Environment Agency is continuing to investigate point and diffuse sources within the Aire and Calder management catchment by undertaking a series of catchment characterisation studies. This will help us identify which sources of metals need to be tackled to achieve the long-term statutory target.
Aire Upper 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 Aire Upper operational catchment.
Table 1. Summary of metal pollution sources in the Aire Upper operational catchment
| Catchment (Surface water body) | Point sources of pollution | Diffuse sources of pollution |
|---|---|---|
| River Aire (Eshton Beck to R Worth) including Cononley Beck | 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 Aire and Calder management catchment, water quality monitoring was undertaken in one of the 7 operational catchments (Aire Upper). This is highlighted 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, 4 monitoring sites were selected across the Aire and Calder 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 Aire and Calder management catchment since 2022.
Water quality monitoring results
In the Aire and Calder 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 and knowledge of the local geology across the catchment indicated that 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: Aire and Calder management catchment
Our detailed monitoring across a range of flow conditions between January 2022 and March 2024 shows that in the Aire and Calder management catchment, the baseline length of polluted rivers for the abandoned metal mines target is 2km.
Figure 2 shows the rivers in the Aire and Calder 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 Aire and Calder management catchment is 2km
© Environment Agency
It should be noted that due to close proximity of some of the sampling points to each other, some of the sampling point markers on this map (blue squares) may overlap.
Table 2 shows the river length (in km) that are polluted by each of the target substances within the Aire and Calder management catchment. In general, the most polluted rivers are impacted by more than one target substance.
Table 2. River length (in km) polluted by each of the target substances within the Aire and Calder 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) | 2 | 0 | 0 | 2 |
| Lead (Pb) | 2 | 2 | 0 | 0 |
| Nickel (Ni) | 0 | 0 | 0 | 0 |
| Zinc (Zn) | 2 | 0 | 0 | 2 |
| Copper (Cu) | 0 | 0 | 0 | 0 |
Rivers polluted by abandoned metal mines: Aire and Calder management catchment
Aire Upper operational catchment: baseline polluted rivers
Cononley Beck is polluted by zinc, lead and cadmium along its length from its source at the former Cononley lead mine down to its confluence with the River Aire. The River Aire downstream of the confluence is not polluted for any of the target substances. The monitoring point on the River Aire at Cononley, which is located upstream of the confluence with Cononley Beck is also compliant and not polluted.
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 Aire and Calder operational catchment is 2km
© Environment Agency