Research and analysis

National groundwater nitrogen inventory and heat maps for England: summary

Published 17 March 2026

Applies to England

1. Chief Scientist’s Group report summary

This project developed and applied an approach to quantify the amount of nitrogen that is at risk of being lost (by leaching) to groundwater each year from a variety of sectors. This work will support the Environment Agency’s approach to fair, evidence-led regulation across the sectors it regulates.

1.1 Background

Elevated nitrogen levels in groundwater remain the primary reason groundwater bodies in England fail to meet chemical quality standards under the Water Framework Directive. Nitrogen in groundwater originates from both agricultural and non-agricultural sources. These includes livestock, application of fertilisers and organic manures, urban sources, and industrial spills.

1.2 Approach

Working with a range of experts from academia and industry, Environment Agency specialists produced a national inventory of the sources and annual amounts of nitrogen leaching to groundwater. The inventory considered thirty-four sectors, subsectors or land use types and collated various data including national statistics, published literature, reports, spreadsheets and maps. The inventory was used to create maps of where nitrogen is at risk of leaching to groundwater in England, for individual sectors and for their combined total.   

1.3 Results

The estimated total nitrogen at risk of leaching to groundwater in England was 665 kilo tonnes of nitrogen (kT N) for 2020.  The largest contribution was from agriculture (549 kT N), with approximately 45% of that from inorganic fertiliser, and 22% from cattle. However, there is considerable uncertainty, with estimates for agriculture ranging from 209 kT N to 888 kT N depending on the analysis methods used. Estimates from the biowaste sector are particularly uncertain due to the wide variability in feedstock composition, processing methods, and data availability across facilities.

The total nitrogen leaching from non-agricultural sectors was estimated to be 116 kT N/yr, with landfill contributing an estimated 45 kT N/yr and industrial spills and leaks contributing 32 kT N/yr. The maps show greater levels of nitrogen leaching from agricultural sources in rural areas. The highest levels from non-agricultural sources were found in heavily urbanised areas such as London, Birmingham, Manchester and Liverpool.

1.4 Conclusions

This work provides the Environment Agency with improved insight into the relative contribution of regulated sectors to groundwater nitrogen. The findings can contribute to wider discussions on reducing nitrogen losses to groundwater. Together, these insights support the Environment Agency approach to equitable and proportionate regulation.  

1.5 Publication details

This summary relates to information from the following project:

• Report: SC210008
• Title: National groundwater nitrogen inventory and heat maps for England                       
• Project managers: Natalie Kieboom and Heidi Bignell, Land Research, Chief Scientist’s Group
• Research contractor: Wardell Armstrong LLP (part of SLR)

This project was commissioned by the Environment Agency’s Chief Scientist’s Group, which provides scientific knowledge, tools and techniques to enable us to protect and manage the environment as effectively as possible.

Enquiries: research@environment-agency.gov.uk.

© Environment Agency