Pentti Åman, Jonna Partanen
Proceedings of the 14th International Peat Congress
ditching-of-mires, mire-lakes, peat-production, water-quality
Theme I. Inventory, stratigraphy and conservation of mires and peatlands
The effects of ditching on water levels and water quality in mire lakes were studied on seven mires located close to peat production areas, six of which possessed a mire lake. The work was carried out chiefly in 2006–2007, although some monitoring results covering several years were included in the data. Groundwater gauges were installed on transects across two mires in order to assess the distance over which ditching affected the mire surface. This parameter was studied more precisely in the case of one of the lakes, Lake Vähä-Karsikkolampi. Water levels were measured in the six lakes, water samples were taken and precipitation was measured throughout the period concerned. Conditions were particularly suitable for such research, as summer 2006 proved to be exceptionally dry.
The results indicate that although the influence of ditching on the surface horizons of the mire extended between 24 m – 38 m from the ditching site, no permanent lowering of the water level could be detected in any of the lakes. Water levels in the lakes and on the mires dropped during summer 2006 on account of the general groundwater situation, but returned to normal with the heavy rains in the autumn. The observations bore witness to the high water retention capacity of peat. No appreciable changes in the water quality of Lake Vähä-Karsikkolampi were detected over the period of peat production.