Research and analysis

Lowland agricultural peat characteristics which influence water quality and peat hydrology: summary

Published 17 August 2026

Applies to England

1. Chief Scientist’s Group report summary

This project investigated the influence of lowland agricultural peat on water quality, the effect peat properties have on water tables, and effective approaches to raising water tables. Literature reviews, field sampling, monitoring and modelling were used to develop new knowledge about peat hydrology and water quality in lowland England. This evidence will help inform sustainable management of lowland agricultural peat that minimises impacts on the water environment.

1.1 Background 

Healthy peatlands are a type of wetland characterised by waterlogged, carbon-rich peat soils made of partially decayed plant matter. Lowland agricultural peatlands account for over a third of England’s peat soils. Drainage of these peatlands for agriculture has caused the peat to degrade, and in doing so, emit greenhouse gases. As a result, lowland agricultural peatlands are the largest source of peat-related greenhouse gas emissions in England, contributing an estimated 2% of the country’s total greenhouse gas emissions.

The main way to reduce emissions from lowland agricultural peat is to raise water tables within the soil. However, the factors influencing water tables in degraded lowland peat soils are poorly understood, so the feasibility and impacts of managing higher water tables in these areas is uncertain. Ditches play an important role in water table management in lowland peat landscapes. They connect fields to the wider drainage network and rivers, meaning that changes in water movement between peat soils and ditches can influence water quality.

1.2 Approach 

Literature reviews were conducted to assess existing data and knowledge gaps on peat properties and water quality in lowland peat areas, informing the project direction. Field data collection included high frequency water table measurements from two locations and water quality measurements from 31 sites representing a wide range of ditches and peats within lowland peat areas. Laboratory analysis generated peat physical property and chemistry data. Modelling was used to explore the influence of peat properties on water table behaviours. A controlled experiment under natural conditions generated experimental data on water quality behaviours associated with raising water tables.

1.3 Results 

Achieving high, stable water tables is likely to be more practical in wetter parts of the country. Water levels in field ditches can influence nearby water tables, but this effect decreases rapidly with distance from the ditch. This means that ditch water levels alone cannot effectively control water table depth across a field. Water tables across a field can vary significantly due to effects of degradation on the physical properties of peat, which reduce its ability to store and move water. Using models, several methods to maintain high, stable peat water tables were explored, including holding ditch water levels high, reduced drain spacing through additional ditches or underdrains, surface or subsurface bunding, and surface irrigation. The best method for an area depends on the local conditions. The study focused on the hydrological effectiveness of different water table management approaches and did not evaluate other considerations, such as their carbon impacts, performance under future climate conditions, or different agricultural water table requirements.

The findings show that water quality in lowland peat areas is context dependent and spatially variable, with water quality differing between places. These differences are influenced by legacy pollution, peat chemistry and type, land use, and water source. Therefore, water quality responses to raised water tables cannot easily be generalised. Concentrations of substances vary through the depth of peat, with evidence of accumulation at depth linked to changes in peat soil oxygen concentration. Raising water tables could lead to the following changes in water quality: reduced concentrations of dissolved organic carbon, nitrate, nitrite and sulfate, and increased concentrations of ammonia, phosphorus, iron and aluminium. Water chemistry data were collected for only part of one season in a single year, preventing assessment of changes in water quality linked to seasonal, annual and interannual variations in substances.

1.4 Conclusions

This project generated comprehensive datasets for surface water and peat chemistry, as well as hydrological and physical properties of lowland agricultural peat. This information provides valuable insight for land managers and policymakers on the feasibility of managing higher water tables in lowland peat areas and the implications for water quality.

1.5 Publication details

This summary relates to information from project SC230026, reported in detail in the following outputs:

• Report: SC230026/R1. Lowland agricultural peat characteristics which influence water quality - literature review

• Report: SC230026/R2. Lowland agricultural peat characteristics which influence peat hydrology - literature review

• Report: SC230026/R3. Lowland agricultural peat characteristics which influence water quality - field and mesocosm studies

• Report: SC230026/R4. Lowland agricultural peat characteristics which influence peat hydrology - in-field water table studies

• Report: SC230026/R5. Lowland agricultural peat characteristics which influence peat hydrology - laboratory and field analysis of peat physical properties

• Report: SC230026/R6. Lowland agricultural peat characteristics which influence peat hydrology - field-scale modelling of water table management

• Report: SC230026/R7. Lowland agricultural peat characteristics which influence peat hydrology - synthesis report

• Science manager: Dr Sian Davies, Chief Scientist’s Group

• Research contractors: University of Liverpool, Cranfield University, UK Centre for Ecology & Hydrology, The Open University and Rigare Ltd.

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