Monitoring in the Wye



Data is key in understanding the environmental challenges within the catchment. The issues are complex, and it will take everybody's effort to improve the Wye to a favourable status. Data evidence will help create a shared understanding of the problems, so everyone can agree the most effective approach and the interventions needed to tackle the issues. Data is being collected at the fastest rate ever as more information is continuously collected through:

  • Monitoring sondes: probes that automatically transmit water chemistry data and turn it into real time information.

  • Autosamplers: devices that collect water samples periodically and are triggered remotely.

  • Remote sensing: the use of drones, aerial photography and satellite images to get a bird's eye view of what is happening on the ground.

  • Citizen science: is scientific research that is carried out by members of the public.

Furthermore, the Environment Agency (EA) routinely monitors the ecological condition of the catchment through:

  • Monthly water chemistry sampling, for chemicals such as phosphorous and nitrogen

  • Twice-yearly (spring and autumn) macroinvertebrate (animals without backbones that can be seen with the naked eye) sampling

  • Twice-yearly (spring and autumn) diatom (a type of microscopic algae) sampling

  • Annual (summer) macrophyte (plants and multi-cellular algae) surveys

  • Monthly growing season (spring-autumn) RAPPER multi-cellular algae surveys.

  • Monthly growing season free-floating (microscopic) water column algae sampling.

  • Fish population surveys using methods such as electric-fishing and seine netting.

All this data contributes to the overall picture of what is happening in the catchment. The evidence can be shared to make evidence-based decisions, and prioritise resources, and actions.

Find out more about algae and algal blooms check out Ecology in the Wye


Image: Sonde in the Wye
River Wye 2023 growing season - Monitoring summary report


This report is an overview of the Environment Agency’s (EA) survey work in the River Wye during the 2023 growing season, which runs from March to September. It focuses on key findings from this year’s water chemistry and algae surveys. This report feeds into our annual Data Analysis Report.

The report found that the 2023 growing season was considerably wetter and cooler than the 2022 growing season, except for May and June. Cooler water temperatures led to reduced levels of filamentous and free-floating algae compared to 2022, which saw prolonged blooms during the summer.

There were 2 dead Atlantic Salmon found in 2023, compared to 64 in 2022. It is likely that cooler water temperatures and increased river volume have reduced the abundance of competitive algae in the Wye and provided better conditions for migrating Atlantic Salmon.

Phosphate levels remain similar to those recorded in 2022, with lower concentrations present in the upper River Lugg in 2023.


The image shows that weather has an impact on the environment. 2022 was warmer and dryer than 2023 and the river volume were lower and river temperatures warmer. In 2022 there were several prolonged algal blooms and sixty four recorded dead Atlantic salmon. However in 2023 the was a lower number of filamentous and free floating algae and only two dead salmon recorded. Years had similar phosphate levels with low concentrations present in the upper river lugg in 2023

You can read the full Growing Season report for 2023


Data Analysis Report for 2023

Our River Wye Data Analysis Report is released annually. The report captures our monitoring data in the Wye Management Catchment, helping to improve our understanding of the causes of changing conditions in the Wye. Our first report was published in 2022 and can be found here.

The 2023 report currently concludes the following:

  • 2023 had cooler river temperatures and was wetter compared to 2022. These conditions resulted in fewer competitive algal groups that thrive off increased temperature and nutrients.
  • Ongoing work suggests that water temperature has a greater influence upon algal communities and blooms in the River Wye than nutrient pollution.
  • The EA only received 2 reports of dead Atlantic salmon in the Wye for 2023, compared to 64 in 2022. Ongoing declines in Atlantic salmon and brown trout populations are apparent in the catchment, declines in Salmon populations are not isolated to the Wye, and a combination of factors including climate change, habitat degradation and pollution are likely to be contributing.
  • Phosphate levels within the main River Wye in England are meeting their target for Special Areas of Conservation (SAC) compliance. However, the River Lugg continues to exceed its target.
  • The latest Water Framework Directive (WFD) classifications were published in 2023, for the period of 2019 to 2022, which indicate a decline in the phosphate status in 11 waterbodies within the English management catchment, all within the Arrow, Lugg and Frome Operational Catchment, whilst 9 waterbodies have improved in status.
  • Water quality data collected by the Wye Alliance citizen scientist groups has been compared with EA data, and although there are some differences, similar phosphate, and nitrogen ‘hotspots’ have been identified with both datasets.
  • The Wye supports a highly significant aquatic macroinvertebrate community in terms of biodiversity and conservation value. With a high diversity of species present, containing many rare and localised species.

Following on from our 2023 report we continue to:

  • Work with the farming community, agricultural supply chain and partners to reduce nutrient input. Significant reduction in nutrients from all sources is required across the whole catchment to contribute to the recovery of river.
  • Carrying out targeted and evidence-based farm inspections and ensure compliance with the regulations.
  • Work with the Wye Alliance to inform our priorities and regulatory activity within the catchment. You can find out more about this on our Citizen Science section.
  • Work with partners on projects to improve river health and water quality, including, research, education, collaboration and delivery across the catchment.
  • Monitor algal blooms in the Wye using sonde data and monitor for any signs of impact on the environment.



Monitoring temperature and algal blooms

  • The EA collect data from the River Wye using sondes. We currently have 4 sondes in the Wye and 1 in the Lugg which provide continuous water quality data. You can see our live sonde data at the following link: MDC - Meteor Data Cloud (telemetry-data.com)

  • The EA continue to monitor water quality throughout the summer months, until the end of September.

Magnified image of the diatom Stephanodiscaceae (showing spines) Read the blog: Environment Agency boosts water quality monitoring to help tackle pollution on the River Wye


RAPPER Surveys and Water Sampling


Monthly Rapid Assessment of PeriPhyton Ecology in Rivers (RAPPER) surveys are a method that is used to identifying macroalgae (algae that can be recognised with the naked eye) growing on the riverbed in a 10metre section of river. In addition to the RAPPER surveys we also take water samples to test for microscopic, free-floating algae and cyanobacteria (blue-green algae), which can turn the water green or brown when present.

RAPPER surveys and free-floating algae surveys take place from May to October within the Wye catchment and the results of these gives us an overall picture of the nutrient enrichment within the water. We undertake these surveys monthly at the same locations as the sondes on the main River Wye. We also use chlorophyll, dissolved oxygen and temperature data collected by the sondes to check for evidence of algal blooms and carry out extra surveys if we suspect an algae bloom is present.


EA officers taking samples in the Wye


Image: A) Bloom forming, free-floating green alga (Dictyosphaerium) present in July 2022; B) A selection of channel bed algae recorded from a RAPPER survey

Graph: Sonde data during an algal bloom (Dictyosphaerium), the increase in chlorophyll levels recorded by the sonde allowed us to detect and sample the bloom.








Data is key in understanding the environmental challenges within the catchment. The issues are complex, and it will take everybody's effort to improve the Wye to a favourable status. Data evidence will help create a shared understanding of the problems, so everyone can agree the most effective approach and the interventions needed to tackle the issues. Data is being collected at the fastest rate ever as more information is continuously collected through:

  • Monitoring sondes: probes that automatically transmit water chemistry data and turn it into real time information.

  • Autosamplers: devices that collect water samples periodically and are triggered remotely.

  • Remote sensing: the use of drones, aerial photography and satellite images to get a bird's eye view of what is happening on the ground.

  • Citizen science: is scientific research that is carried out by members of the public.

Furthermore, the Environment Agency (EA) routinely monitors the ecological condition of the catchment through:

  • Monthly water chemistry sampling, for chemicals such as phosphorous and nitrogen

  • Twice-yearly (spring and autumn) macroinvertebrate (animals without backbones that can be seen with the naked eye) sampling

  • Twice-yearly (spring and autumn) diatom (a type of microscopic algae) sampling

  • Annual (summer) macrophyte (plants and multi-cellular algae) surveys

  • Monthly growing season (spring-autumn) RAPPER multi-cellular algae surveys.

  • Monthly growing season free-floating (microscopic) water column algae sampling.

  • Fish population surveys using methods such as electric-fishing and seine netting.

All this data contributes to the overall picture of what is happening in the catchment. The evidence can be shared to make evidence-based decisions, and prioritise resources, and actions.

Find out more about algae and algal blooms check out Ecology in the Wye


Image: Sonde in the Wye
River Wye 2023 growing season - Monitoring summary report


This report is an overview of the Environment Agency’s (EA) survey work in the River Wye during the 2023 growing season, which runs from March to September. It focuses on key findings from this year’s water chemistry and algae surveys. This report feeds into our annual Data Analysis Report.

The report found that the 2023 growing season was considerably wetter and cooler than the 2022 growing season, except for May and June. Cooler water temperatures led to reduced levels of filamentous and free-floating algae compared to 2022, which saw prolonged blooms during the summer.

There were 2 dead Atlantic Salmon found in 2023, compared to 64 in 2022. It is likely that cooler water temperatures and increased river volume have reduced the abundance of competitive algae in the Wye and provided better conditions for migrating Atlantic Salmon.

Phosphate levels remain similar to those recorded in 2022, with lower concentrations present in the upper River Lugg in 2023.


The image shows that weather has an impact on the environment. 2022 was warmer and dryer than 2023 and the river volume were lower and river temperatures warmer. In 2022 there were several prolonged algal blooms and sixty four recorded dead Atlantic salmon. However in 2023 the was a lower number of filamentous and free floating algae and only two dead salmon recorded. Years had similar phosphate levels with low concentrations present in the upper river lugg in 2023

You can read the full Growing Season report for 2023


Data Analysis Report for 2023

Our River Wye Data Analysis Report is released annually. The report captures our monitoring data in the Wye Management Catchment, helping to improve our understanding of the causes of changing conditions in the Wye. Our first report was published in 2022 and can be found here.

The 2023 report currently concludes the following:

  • 2023 had cooler river temperatures and was wetter compared to 2022. These conditions resulted in fewer competitive algal groups that thrive off increased temperature and nutrients.
  • Ongoing work suggests that water temperature has a greater influence upon algal communities and blooms in the River Wye than nutrient pollution.
  • The EA only received 2 reports of dead Atlantic salmon in the Wye for 2023, compared to 64 in 2022. Ongoing declines in Atlantic salmon and brown trout populations are apparent in the catchment, declines in Salmon populations are not isolated to the Wye, and a combination of factors including climate change, habitat degradation and pollution are likely to be contributing.
  • Phosphate levels within the main River Wye in England are meeting their target for Special Areas of Conservation (SAC) compliance. However, the River Lugg continues to exceed its target.
  • The latest Water Framework Directive (WFD) classifications were published in 2023, for the period of 2019 to 2022, which indicate a decline in the phosphate status in 11 waterbodies within the English management catchment, all within the Arrow, Lugg and Frome Operational Catchment, whilst 9 waterbodies have improved in status.
  • Water quality data collected by the Wye Alliance citizen scientist groups has been compared with EA data, and although there are some differences, similar phosphate, and nitrogen ‘hotspots’ have been identified with both datasets.
  • The Wye supports a highly significant aquatic macroinvertebrate community in terms of biodiversity and conservation value. With a high diversity of species present, containing many rare and localised species.

Following on from our 2023 report we continue to:

  • Work with the farming community, agricultural supply chain and partners to reduce nutrient input. Significant reduction in nutrients from all sources is required across the whole catchment to contribute to the recovery of river.
  • Carrying out targeted and evidence-based farm inspections and ensure compliance with the regulations.
  • Work with the Wye Alliance to inform our priorities and regulatory activity within the catchment. You can find out more about this on our Citizen Science section.
  • Work with partners on projects to improve river health and water quality, including, research, education, collaboration and delivery across the catchment.
  • Monitor algal blooms in the Wye using sonde data and monitor for any signs of impact on the environment.



Monitoring temperature and algal blooms

  • The EA collect data from the River Wye using sondes. We currently have 4 sondes in the Wye and 1 in the Lugg which provide continuous water quality data. You can see our live sonde data at the following link: MDC - Meteor Data Cloud (telemetry-data.com)

  • The EA continue to monitor water quality throughout the summer months, until the end of September.

Magnified image of the diatom Stephanodiscaceae (showing spines) Read the blog: Environment Agency boosts water quality monitoring to help tackle pollution on the River Wye


RAPPER Surveys and Water Sampling


Monthly Rapid Assessment of PeriPhyton Ecology in Rivers (RAPPER) surveys are a method that is used to identifying macroalgae (algae that can be recognised with the naked eye) growing on the riverbed in a 10metre section of river. In addition to the RAPPER surveys we also take water samples to test for microscopic, free-floating algae and cyanobacteria (blue-green algae), which can turn the water green or brown when present.

RAPPER surveys and free-floating algae surveys take place from May to October within the Wye catchment and the results of these gives us an overall picture of the nutrient enrichment within the water. We undertake these surveys monthly at the same locations as the sondes on the main River Wye. We also use chlorophyll, dissolved oxygen and temperature data collected by the sondes to check for evidence of algal blooms and carry out extra surveys if we suspect an algae bloom is present.


EA officers taking samples in the Wye


Image: A) Bloom forming, free-floating green alga (Dictyosphaerium) present in July 2022; B) A selection of channel bed algae recorded from a RAPPER survey

Graph: Sonde data during an algal bloom (Dictyosphaerium), the increase in chlorophyll levels recorded by the sonde allowed us to detect and sample the bloom.






Page last updated: 16 Aug 2024, 10:08 AM