Hydrology and water quality in managed peatlands of northern Finland: effects of peat thickness and water table management
Thesis event information
Date and time of the thesis defence
Place of the thesis defence
OP-Pohjola auditorium (L6), Linnanmaa Campus
Topic of the dissertation
Hydrology and water quality in managed peatlands of northern Finland: effects of peat thickness and water table management
Doctoral candidate
Master of Science Tung Pham
Faculty and unit
University of Oulu Graduate School, Faculty of Technology, Water, Energy and Environmental Engineering
Subject of study
Environmental Engineering
Opponent
Senior Researcher Per-Erik Mellander, Teagasc – the Agriculture and Food Development Authority, Ireland
Custos
Professor Hannu Marttila, University of Oulu
Hydrology and water quality in managed peatlands of northern Finland: effects of peat thickness and water table management
Peatlands are commonly drained for crop cultivation, but drainage also changes how water moves through the soil. This can increase the amounts of nutrients, organic carbon and acidifying substances reaching nearby waters, potentially harming water quality. Understanding how peat thickness and changing water levels affect these losses can help reduce the environmental impacts of agriculture on peat soils.
This dissertation combined several years of monitoring at a cultivated peat field in northern Finland with a laboratory experiment using intact peat samples from areas with different land uses. The field had controlled subsurface drainage, peat of varying thickness and sulfur-rich material beneath the peat that can produce acidity when exposed to oxygen. The studies examined how peat thickness and water-level changes influence water flow, chemical processes within the peat, and the quality of drainage water.
Most water left the field via subsurface drains. The greatest losses of nutrients and other substances occurred during spring snowmelt, winter thaws and wet autumn periods. Nitrogen losses were substantial, mainly as nitrate, especially where the peat was thicker and the soil was bare or crops were still developing. Nitrate concentrations and losses declined considerably under established perennial grass cover. Phosphorus losses through the drains were relatively small, but water flowing over the soil surface could carry a substantial share of the total phosphorus lost from the field. Organic carbon losses increased with peat thickness. High sulfate and acidity loads suggested oxidation of sulfur-rich soil beneath the peat during periods of low groundwater levels.
In the laboratory experiment, changing water levels affected dissolved organic carbon, iron and sulfate. Nutrient levels in water within the peat differed between soil layers, but the water draining from the samples contained low concentrations of inorganic nitrogen and phosphorus.
Overall, the findings show that water quality impacts from cultivated peatlands depend on several interacting factors: changing water levels, peat thickness, vegetation, the underlying soil and season. Drainage and water-level management should consider local field conditions to reduce nutrient losses and acidification risks.
This dissertation combined several years of monitoring at a cultivated peat field in northern Finland with a laboratory experiment using intact peat samples from areas with different land uses. The field had controlled subsurface drainage, peat of varying thickness and sulfur-rich material beneath the peat that can produce acidity when exposed to oxygen. The studies examined how peat thickness and water-level changes influence water flow, chemical processes within the peat, and the quality of drainage water.
Most water left the field via subsurface drains. The greatest losses of nutrients and other substances occurred during spring snowmelt, winter thaws and wet autumn periods. Nitrogen losses were substantial, mainly as nitrate, especially where the peat was thicker and the soil was bare or crops were still developing. Nitrate concentrations and losses declined considerably under established perennial grass cover. Phosphorus losses through the drains were relatively small, but water flowing over the soil surface could carry a substantial share of the total phosphorus lost from the field. Organic carbon losses increased with peat thickness. High sulfate and acidity loads suggested oxidation of sulfur-rich soil beneath the peat during periods of low groundwater levels.
In the laboratory experiment, changing water levels affected dissolved organic carbon, iron and sulfate. Nutrient levels in water within the peat differed between soil layers, but the water draining from the samples contained low concentrations of inorganic nitrogen and phosphorus.
Overall, the findings show that water quality impacts from cultivated peatlands depend on several interacting factors: changing water levels, peat thickness, vegetation, the underlying soil and season. Drainage and water-level management should consider local field conditions to reduce nutrient losses and acidification risks.
Created 15.10.2026 | Updated 16.10.2026