River Wye Water Quality

Closes 31 Mar 2024

Opened 5 Apr 2022


Welcome to this information page which explains the Environment Agency’s analysis, activities and plans to improve water quality, reduce excess nutrients, and help improve environments in the Wye and Lugg river catchments.  

Whilst this focuses on the Environment Agency’s work, there are many key organisations and community groups involved. They are helping monitor water quality, planning and taking actions to reduce nutrients and support river recovery, and supporting others to have a role. Links are provided below to our partners’ websites. 

This page will be updated with new data (quarterly), actions taken, trends, information and case studies on the Environment Agency’s work. 

To report a pollution incident, if you observe an algal bloom or if you see fish in distress: call the EA’s incident hotline: 0800 80 70 60 or email ics@environmentagency.gov.uk with details of the issue, location and ideally photographs. 

Information for citizen scientists sampling water quality is below.


Latest news

Current situation

Which organisations are working together?

Role of the Environment Agency, Natural England and Natural Resources Wales


Actions ongoing

Citizen Science Programme

Additional information / FAQs

Latest news

  • In April 2022 we released our latest quarterly monitoring report – (River Wye Management Catchment Integrated Data Analysis Report) - see below.
  • See our 2021 agricultural regulation enforcement outcomes – below.
  • We are monitoring for possible algal blooms as warmer weather approaches.

More Information

  • Algae occur naturally in inland waters such as rivers, streams and lakes.
  • Algal blooms as seen on the River Wye and River Lugg are caused by a number of factors that include nutrient enrichment, environmental factors (sunny warm weather and low flows), hydrodynamics, microbes and biodiversity.
  • The Environment Agency is continuing to monitor the river. We have equipment specifically deployed recently to monitor river temperatures and quality – in addition to routine monitoring. We continue to work with partners on long term actions to improve water quality.
  • During a bloom, the water becomes less clear and may look green, blue-green or greenish-brown. Scums can form during calm weather when several bloom forming species rise to the surface. This can look like paint, mousse or small clumps. Algal blooms block sunlight from reaching other plants in the water. They also use up oxygen in the water at night which can suffocate fish and other wildlife. Oxygen is also used up when the bloom decays.
  • Cyanobacteria or ‘blue-green algae’, a type of blooming algae, can produce toxins. Blue-green algae is a naturally occurring environmental phenomenon that becomes more likely to occur during periods of warm, settled, dry weather or after periods of heavy rain. The algae poses a small risk to human health if a person comes into direct contact with it, however it can pose risk to animals such as dogs if they drink or swim in affected water.
  • Please keep pets and children away from the water and avoid skin contact with the water or algae.
  • If you suspect blue-green algae or see dead fish / fish in distress please contact the Environment Agency’s 24-hour incident hotline on 0800 80 70 60 so that we can inform relevant landowners and ask them to take the necessary steps to warn the public of potential dangers.
  • Advice on algal blooms for landowners and members of the public is available here

Current situation

The Environment Agency is concerned about high phosphate levels in the Wye and Lugg catchments. We are working closely with a range of stakeholders and partners to address these concerns.  

Phosphate originates from two main sources. These are discharges from sewage treatment works which are regulated through Environmental Permits and from diffuse agricultural pollution, principally from livestock manure and nutrients washing into the river during rainfall events. More than 60% of phosphate (varying across the catchment) entering rivers is from agriculture

Which organisations are working together?

The Environment Agency, Natural England, Natural Resources Wales, Herefordshire Council, Powys Council, and Dwr Cymru Welsh Water all work together on the River Wye Nutrient Management Plan (NMP) (and associated Action Plan). The NMP Board and Technical Advisory Group involves key stakeholders (including water companies and farming support organisations and local authorities). 

We are working together to address the causes and impacts of high phosphate levels, through a combination of advice and guidance, regulation and the delivery of projects to reduce phosphate inputs. 

As part of our advisory role, the Environment Agency is a partner in Farm Herefordshire - a group of organisations set up to support the farming community in delivering Nutrient Management Plan objectives, particularly from agricultural diffuse pollution. Further details can be found here: http://wyecatchment.org/farm-herefordshire/   

We also regulate the agriculture and water industries so our work includes targeted agricultural visits and working with Dwr Cymru Welsh Water to reduce phosphate in the catchment from sewage treatment works. 

Role of the Environment Agency, Natural England and Natural Resources Wales

The Environment Agency's role is to:

  • To regulate the activities that have the biggest effect on water quality in our rivers, primarily the water and sewerage companies, farmers and industry. 
  • To set permitting rules of water companies (and others) and monitor and enforce these.  
  • Monitor data and track intelligence to target agricultural regulatory and enforcement activity.  
  • Understand and track the quality of the river.  
  • Work with farmers to drive better compliance and tackle inadequate farm infrastructure and poor soil and nutrient management.  
  • To be involved in partnership projects, protecting and enhancing water quality through Water Framework Directive and River Basin Management Plans.

More Information

  • To monitor the condition of the River Wye and ensure habitat features are in a healthy state and being conserved by appropriate management.  

  • To assess whether proposals to carry out operations within a SSSI have a positive or negative effect on the condition of a site. 

  • Advise Herefordshire Council and Gloucestershire County Council on their Local Nature Recovery Strategy. 

  • Advice and approval for grants to delivery improvements for air and water quality through the joint Natural England/Environment Agency Catchment Sensitive Farming Programme, as well advice to farmers through Agri-environment agreements.  

  • See Designated Sites information

More Information

  • To manage the environment in the most beneficial way, taking account of social, economic and environmental needs.  

  • To regulate and to protect people and the environment by ensuring that businesses and individuals operate within the law when their actions impact on the environment. For water quality this means setting rules and regulating water companies, farmers, developers and industry, 

  • As a statutory consultee for planning applications, providing advice on how a development may affect the environment. This includes possible damage to important habitats, wildlife, rivers and landscapes,. 

  • To gather evidence to develop our knowledge of the environment in Wales, in conjunction with a wide range of partners. This includes running sampling and monitoring programmes  

  • Advise the Welsh Government, to industry and to the wider public and voluntary sector - advising on​ how new policies, legislation, developments and their day to day work affects the environment.  

  • See Water Watch Wales maps 


To appropriately focus everyone’s resources and actions on reducing nutrients entering the rivers, we need to understand nutrient levels and how phosphate is moving - runoff from fields but also through drainage systems. The soil chemistry is another area under investigation – for example even if we stopped adding more phosphate immediately phosphate could still be leaching out for many years. 

The Environment Agency will release a quarterly report analysing catchment data from multiple sources. This is vital evidence to show what is happening in the catchment and determine priority actions. 

We recognise – and are grateful – that many people are keen to support efforts to improve the water in the Wye and Lugg catchments through Citizen Science initiatives.  

The data obtained by Citizen Science groups will complement existing Environment Agency monitoring and data.   

Citizen science data has not been analysed for the April 2022 report as the Environment Agency received the data after the data-cut-off date for this report. It will be included in future reports. 

All the information, from the Environment Agency and Citizen Scientists, will inform how we plan and prioritise activity across the entire catchment and will determine the locations where our resources are most needed and can have the most impact. 

We have also sought independent evidence through the recent RePhoKus project by Lancaster University which carried out a system level analysis of phosphate in the catchment. Details are due to be published soon.  

The Environment Agency’s River Wye Management Catchment Integrated Data Analysis Report 

We will bring data from monitoring sondes and autosamplers together with existing datasets four times a year to answer the following questions to contribute to a shared understanding and ownership among all stakeholders of the issues and actions required:  

   1. What are the main variables contributing to algal blooms in the Wye?  

   2. What other ecological and water quality issues does the data show?  

        a. When did these occur?  

        b. Where did these occur?  

   3. Which locations, sectors and activities were responsible for the ecological and water quality issues identified in the data?  

   4. What recommendations can be made for regulatory, partnership and industry sector actions to prevent the reoccurrence of ecological and water quality issues identified in the data?  

The full report can be downloaded here. A detailed summary is below (after the visual summary) .


A simplified visual summary of the River Wye Management catchment Integrated Data Analysis Report.    Please refer to the full report to understand the detail and areas of uncertainty. For this report, the Environment Agency analysed data made available to us up to the cut-off date of 31st October 2021.   Based on that data we can conclude that increases in arable land cover, extreme water temperatures and sewage discharges are contributing to algal blooms on the Wye.   Nitrogen concentrations are increasing throughout the catchment.   Phosphate concentrations are increasing in tributaries of the main Wye.   Salmon populations are declining throughout the catchment.   Aquatic plants are affected by eutrophication throughout the catchment.   Regulators, catchment partners and industry sectors need to work together to reduce nutrient inputs from all sectors, increase river shade, collect and share more data and target upstream catchments

More Information

  • Additional data and analysis 

    There is a large amount of citizen science monitoring that has taken place within the Wye catchment by third parties in the past year. This data was not made available to the Environment Agency in time for this report. In the future, citizen science data needs to be analysed to increase the temporal and spatial resolution of orthophosphate data in the catchment. We will include as much citizen science data as possible in future reports.  

    Further investigations into the species of algae involved in blooms on the Wye are required to determine more conclusively whether free floating or benthic algae is more of a problem and whether this interaction changes over the course of a bloom event. We are developing an algal monitoring programme to do this during 2022. 

    Further work is also required to assess the sources of nutrient uptake to macrophytes and algae which are not detectable by water column monitoring. Sediment sampling especially, should be explored to fill this gap in understanding. We will pursue all available funding and delivery routes for this, including asking for support from partners where our resources do not allow us to undertake the desired sampling. 

    Describing the habitat through Habscore and River Habitat Surveys would help in understanding the interplay between the physical conditions and biological communities and contribute to understanding the impacts of climate change on habitat availability. 

    Our future analysis of invertebrate data will involve Hydroecological validation (HEV).  By incorporating hydrological data, we can analyse patterns in measured flow and the condition of the ecological community. We can also use HEV to infer the effect of other pressures, such as sediment and morphology on the invertebrate population. 

    More detailed time series data on volumes spilled by Combined Sewer Overflows (CSOs) is required to rigorously assess the relative contribution that such sources play. We will ask for support from partners, particularly Dwr Cymru Welsh Water to contribute this information to the shared understanding in the catchment. 

    Targeting Regulatory and Partnership Action  

    While more information is still required to provide more detailed recommendations to support targeted action, we can recommend the following:  

    Efforts to increase shade by tree planting and better management of riparian trees could help mitigate high temperatures.   

    Extreme reduction in nutrient input from all sources is required across the whole catchment to contribute to the recovery of river macrophytes.  

    Taking a catchment-based approach, all contributing partners in the Wye Management Catchment could target investigations, analysis and remedial actions in key focus catchments that meet the following criteria:  

    • As far upstream as possible  

    • High phosphate concentrations relative to the wider catchment  

    • A high proportion of the following factors and drivers are present:  

    • Arable land use  

    • Maize  

    • Poultry sheds  

    • Anaerobic digesters  

    • Sewage treatment works  

    • Combined sewer overflows  

    • Macrophytes status less than good and indicative of eutrophication  

    • Declining Atlantic salmon populations  

    • Land allocated for development to which Nutrient Neutrality guidance applies  

    • Active citizen science groups  

    • Active partnership projects  

    Based on these criteria the following functional groups of waterbodies seem most suitable initially:  

    1. River Arrow near Kington  

    1. River Arrow near Pembridge and Curl Brook  

    1. River Lugg and tributaries near Presteigne  

    1. Little Lugg and Withington Marsh Brook  

    1. River Frome  


    Summary of Conclusions  

    We can currently conclude, based on the latest available data, tha

    1. What are the main variables contributing to algal blooms in the Wye?   
    • Significant algal growth occurs on the main River Wye during the summer. A large amount is filamentous algae and diatoms covering the riverbed. The relative proportion of riverbed to free floating algal growth is currently unknown. 
    • Excessively high summer water temperatures on the main River Wye are a major contributing factor to this algal growth. 
    • Water column phosphate concentrations are low where the algal blooms have been recorded. More frequent and widespread orthophosphate, total phosphorus, and sediment nutrient data is required in partnership, to test whether this means other factors are more important triggers of algal blooms. 
    • Water column nitrogen concentrations are too high everywhere in the catchment but would not trigger algal blooms if phosphate availability to aquatic plants were low enough to limit growth. 


    1. What other ecological and water quality issues does the data show?   
    • Salmonid fish populations have declined over the last 10 years, and there has been a shift to the headwaters of the Lugg for the main Atlantic salmon population in the English sections of the Wye. 
    • Invertebrate populations currently appear to be healthy, although additional metrics need to be explored. 
    • Macrophyte communities sampled in 2021 show evidence of eutrophication across the whole catchment. 
    • Nutrients within the water column are a bigger problem in tributaries than the main Wye. Sediment analysis is needed to build a more complete understanding. Since 2010, there has been an increasing trend in orthophosphate on tributaries of the Wye and an increasing trend in nitrogen across most of the catchment. 


    1. Which locations, sectors and activities were responsible for the ecological and water quality issues identified in the data?  
    • Arable agriculture, particularly maize and autumn sown crops like winter wheat on permeable soils contribute significantly to orthophosphate concentrations. 
    • There has been an extreme increase in the proportion of land managed as arable since 2016, particularly maize and potato crops, which are more susceptible to soil loss. 
    • Sewage treatment works (STW) and combined sewer overflow (CSO) discharge rates are significant contributing factors to orthophosphate concentrations. STW phosphorus limits are effective in reducing the contribution to orthophosphate concentrations, however, CSOs and agriculture appear to contribute towards target exceedance where phosphate limits are in place. 
    • The number of poultry units in a catchment does not show a clear correlation with orthophosphate levels but does appear show a link with nitrogen levels and total phosphorus. Total phosphorus data is currently too sparse to demonstrate a causal relationship and this analysis does not account for pathways of impact outside the unit such as spreading of manure or digestate on fields outside the catchment where the poultry units themselves are located. Further investigation is needed to demonstrate that this is a cause and confirm the pathways. 
    • Sewage discharge and agriculture account for the largest share of environmental incidents reported to the Environment Agency in the Wye Management Catchment between 1 November 2020 and 31 October 2021. 


    1. What recommendations can be made for regulatory, partnership and industry sector actions to prevent the reoccurrence of ecological and water quality issues identified in the data?  
    • Efforts to increase shade by tree planting and better management of riparian trees could help mitigate high temperatures. 
    • Extreme reduction in nutrient input from all sources is required across the whole catchment to contribute to the recovery . 
    • Taking a catchment-based approach all contributing partners in the Wye Management Catchment could target key focus catchments based on criteria identified in this report. 

Public access to our monitoring and environmental data is available at: https://environment.data.gov.uk/water-quality/view/explore  

All our open data is available at: Defra Data Services Platform  

This page has a gallery of easy to use apps for viewing our various open data sources Defra Data Services Platform 


Actions ongoing

The Environment Agency’s role is to regulate the water and agricultural industries and monitor water quality.


Dwr Cymru Welsh Water is taking action to reduce phosphate in the catchment from sewage treatment works:

  • Dwr Cymr Welsh Water have a funded programme of investment on a number of sewage works in the catchment which will significantly reduce the contribution from sewage works by 2025.
  • Larger sewage treatment works currently have (or will have by 2025) phosphate limits – and for example are adding phosphate strippers.
  • With smaller works, initiatives such as the development of integrated wetlands are helping reduce their phosphate load.

The Environment Agency adopts a targeted regulatory approach – in line with our enforcement and prosecution policy / guidelines and because it is not possible to check every one of the thousands of farms in the catchment.

Our agricultural compliance and regulatory activity uses monitoring data, real time satellite and drone information, runoff-risk maps and intelligence from previous incidents and public reports to identify and target locations at high risk of contributing to nutrient and soil pollution.

  • The New Farming Rules for Water for all farmers in England were introduced by Defra in 2018. The rules are designed to help protect water quality by standardising good farm practices and require farmers to: keep soil on the land; match nutrients to crop; and soil needs; and keep livestock; fertilisers and manures out of the water.
  • Environment Agency farm inspections are advice-led, with officers taking a proportionate approach that uses advice and guidance first, reflects individual circumstances and only seeks sanction where farmers repeatedly fail to take necessary action. 
  • We have reminded farmers that they are legally obliged to test soils and to prevent significant run-off. Any breach of the regulations may result in an investigation and enforcement action being considered.  
  • Defra funding nationally has allowed the recruitment of additional office to regulate agricultural activity – including 4 permanent posts focused on the River Wye catchments. Officers will be increasing farm visits, focusing on high-risk locations and previously non-compliant businesses.  

An extensive programme of advisory and support work is delivered by catchment Sensitive Farming and catchment partners, including the Wye and Usk Foundation, Herefordshire Wildlife Trust and Farm Herefordshire to reduce agricultural sources of pollution to the River Wye. 

Project Tara:

We are working with the poultry industry to understand the scale of poultry manure production and use in the River Wye catchment. We are also working with the anaerobic digestion and dairy industries for a similar purpose with regards to their manure production and use. We are carrying out regulatory assessments to ensure compliance with the Reduction and Prevention of Agricultural Diffuse Pollution Regulations and the Nitrate Pollution Prevention Regulations. These checks aim to ensure that the nutrients within the poultry manure are being utilised effectively for crop production and do not pose a risk of causing diffuse pollution.


Across the Wye and Lugg catchments in 2021 we carried out 137 inspections in areas at risk of causing diffuse agricultural pollution. The areas were identified using our monitoring network (such as satellite data, Lidar, and drones) and reports of pollution.  

This included: 

  • 101 Farming Rules for Water inspections of high-risk fields and sites  
  • 15 integrated farm inspections including a project focusing on dairy and anaerobic digestion sites  
  • 21 intensive farm inspections including a project focusing on poultry regulation.  

Of the 137 inspections, we used regulatory powers in 36 instances to require land managers to come into compliance. This included providing regulatory advice and guidance and signposting to additional support offered by partner organisations such as the Wye and Usk Foundation. In total we issued ten warning letters.  

We recruited several new officers in the latter half of 2021 to enable more farm visits.

See below Frequently Asked Questions section for more on our monitoring role and our role in intensive poultry units.


Citizen Science Programme

We are working with a variety of partners in the development and delivery of a Citizen Science monitoring programme. This additional resource will be used to collect water quality data throughout the Wye catchment and will help to identify and prioritise where measures can be targeted to reduce inputs of pollution.  

We politely request Citizen Scientists to follow our data collection and reporting guidance to ensure the data can be used effectively

Where Citizen Science groups identify pollution incidents (including algal bloom, dead fish or fish in distress) these should be reported to the Environment Agency via the 24hr Incident Hotline: 0800 80 70 60.

Please do not report high phosphate readings to the incident hotline – report them as usual through the collector app.

Please note the Environment Agency will only attend incidents which are categorised by the Common Incident Classification Scheme (CICS) as serious/significant. Less severe environmental incidents will be recorded on our data systems and used to target investigations, regulation, campaigns, water quality planning, projects and partnership working.

Additional information / FAQs

What is the Environment Agency’s role in monitoring?

The Environment Agency has long term data and trend information on water quality in the English Wye and Lugg and will continue to prioritise this baseline information in the Special Area of Conservation (SAC) waterbodies to support our working.

We aim to be more flexible and agile in where we focus monitoring and investigative resources throughout the wider catchment and we are continuing to develop bespoke monitoring programmes to allow better identification of hotspots and cross-border issues. 

This will enable us to respond more rapidly and effectively when at-risk areas are identified through intelligence from satellite images and other environmental monitoring (for example water quality issues identified during invertebrate and other catchment surveys or use of use of phosphate sondes detectors). 

We plan to also use the results of citizen science and third- party monitoring to add to our catchment knowledge.  

Our data analysis and identification and investigation of how moves through the catchment will allow all partners to plan appropriate advice and regulation measure.  

The Nutrient Management Plan Board considers cross border matters and recognises the need for a coordinated approach to data analysis and monitoring across the Wye/Lugg catchments. Discussions between Environment Agency and Natural Resources Wales are underway to develop a suitable programme.    

Intensive Poultry Unitswhat is the Environment Agency’s role?

The planning process is the responsibility of the local planning authority, such as Herefordshire Council for the English part of the River Wye.

The Environment Agency regulates intensive poultry units. Operators must also apply to the Environment Agency for an environmental permit if they rear poultry intensively, defined as an installation with more than 40,000 places for poultry.

The Environment Agency’s decision whether to grant an environmental permit is separate from the planning process.   

A new development will need to have both planning permission and an environmental permit before it can operate.   It is possible for a site to be granted planning permission and not granted an environmental permit or vice versa.   

Frequently Asked Questions

We have developed these answers to frequenly asked questions that are currently being asked by citizen scientists.


If you have questions or queries, or you would like to provide feedback to us on any of the information above, you can get in touch with us at enquiries_westmids@environment-agency.gov.uk


  • Recreational and commercial river users
  • Fishing clubs and representative associations
  • Members of the public with an interest in the river, the species and conservation
  • Businesses
  • Charities
  • Statutory organisations
  • NGOs
  • Members of the public
  • Elected representatives, including MPs
  • Local councils
  • Academics
  • All water abstractors
  • Environment Agency customers
  • Net fishing license holders
  • River based salmon angling owners/fishing clubs/organisations
  • Individual migratory salmonid licence holders
  • Business that buy salmon/supported by salmon net and rod fishing
  • National based fishery, conservation and landowner organisations
  • Government family organisations
  • IDBs
  • Local authorities
  • District and parish councils
  • Environmental bodies
  • Land owners
  • Farming associations
  • Drainage associations
  • RFCCs
  • Elected representatives, including MPs
  • Water companies
  • Members of the public
  • Recreational and commercial river users
  • Community groups
  • Flood action groups
  • Environment Agency colleagues


  • Water quality
  • Habitats and wildlife