How to find water for groundwater table management in cultivated peatlands? – Catchment based approach

Cultivated peatlands cause greenhouse gas emissions and nutrient leaching into water courses but are often important for local agriculture. Water table management, namely raising the water table (WT) in the soil horizon with controlled drainage or subirrigation, has been suggested as the most important management option for minimizing environmental impacts while continuing conventional agriculture. However, in many regions, including the Finnish west coastal areas near Bothnian Bay, it is difficult to obtain sufficient water volume for subirrigation purposes. Even with a flat topography and positive annual water balance, many cultivated fields require additional water input (subirrigation) if a higher-than-normal water table is desired during the summer. In areas with low lake percentages, this would require utilization of runoff from the upper catchment areas or storage of springtime excess water if summertime runoff is insufficient.

This project aims to improve practical knowledge and form an analytical framework to assist water management in cultivated peatlands. We measure WT fluctuations and soil physical properties, bulk density, and loss on ignition from 11 cultivated peatlands in the North Ostrobothnian region, and analyze the upper catchment properties, including the catchment area, soil surface, land use, and flow network for individual fields. We use WT and soil property measurements to analyze potential subirrigation needs for study fields, and catchment data to calculate the potential for upper catchment areas to produce or store the required water volumes. This analysis is used to form a practical framework for using a catchment-scale approach to address water management challenges in cultivated peatlands.