Indicative catchment statistics for nutrient pollution: executive summary
Updated 1 October 2024
Applies to England
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The Environment Agency has provided indicative, catchment-scale source apportionment and estimated diffuse sector reductions required to meet protected area water quality targets. This is to support a general understanding of catchments and is not intended to give the level of detail needed to inform specific on-the-ground measures. This will help those designing or co-ordinating nutrient mitigation schemes, working on diffuse water pollution plans (DWPPs) and working on site restoration.
We have highlighted the dominant sources of nutrients under the ‘recent’ scenario, to closely represent what is currently happening in catchments. The results should be regarded as indicative. They will be superseded by further modelling work for DWPPs where indicated, which will also incorporate the ‘at permit’ scenario simulations of the point sector fully utilising all permit headroom and the benefits of water industry investment to reduce point source pollution since 2020 (AMP7) and in the future (PR24).
We used Simcat SAGIS models calibrated using monitoring data up to 2020. We applied the revised ‘polluter pays principle’ methodology to define the ‘fair share’ percentage reduction required by each broad sector. We compared the diffuse sector figures to outputs from Farmscoper, which show what may be achieved by improvements to land management.
We have also presented the reduction required by the point sector for each catchment. However, this report does not set out the reductions that have been achieved by the AMP7 water company investment measures nor future PR24 schemes, including the proposed improvements to wastewater treatment works to comply with the Levelling up and Regeneration Act. The work for the DWPPs will consider these further.
We have not quantified the additional nutrient contributions from any future development and growth including housing. Any additional future nutrient load will be assessed through the planning process led by the local planning authority or through our permitting process.
The results show that rural land use sources of nutrients dominate most catchments, particularly the rivers. A small number of catchments have diffuse urban sources indicated and point sources are important in most catchments.
In almost all catchments, we estimate the ‘fair share’ reduction required by the diffuse sector to be several times greater than the estimated reduction in losses achieved when applying catchment-wide rural land management measures. This is where additional or alternative measures would need to be explored to achieve the diffuse sector share of the target.
For more information, read the full report.