Page 14 - Tallinna Ülikool

5.
Restoration increases the role of mires in the hydro- logical cycle
By closing ditches in drained mires we improve groundwater supply and reduce extremes of the surface water – increase water level in dry periods and decrease extreme floods.
By restoring mires in Estonia we can increase the naturalness of the hydrological systems there.
Mires are part of a hydrological network that links streams, rivers, lakes, water ows, water levels and water quality. Mires o en reduce the extent and intensity of oods. Dry peat absorbs water, thus reducing the damage caused by high water. On average there is only 5% dry matter in peat; 95% of the peat is lled with water. During dry weather, the peat grad- ually releases water, which can continue for
a long time. However, if the peat is saturated with water, rainwater or snowfall moves into ditches, streams and rivers, increasing their ow and raising water levels.
As peat formation in mires requires high wa- ter levels during most of the year, on drained peatlands the surplus water drains quickly in times of abundant water supply. Intensively drained peatlands and severely degraded peat soils, on the ohter hand, will increase peak charge rates again. Only undrained mires can store a large quantity of water at the surface and have a bu ering e ect on catchment hydrology.
Kukka springfen in Hiiumaa / T. Leito
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TEN REASONS TO RESTORE ESTONIAN MIRES / 2019