Water quality in cutaway peatland lakes in Seda mire, Latvia

Remediation of industrially-milled peatland is an important task in the sustainable management of natural resources. Several approaches for wetland restoration, depending on local climatic and hydrological conditions, topography, physico-chemical properties of peat, as well as peat mining techniques, have been developed worldwide. However, most of the restoration activities include regulation of hydrological regime and surface topography in order to reintroduce typical bog vegetation, especially, Sphagnum cover, and to restore the peatland’s ecosystem close to its original conditions (Gorham and Rochefort, 2003; Farrell and Doyle, 2003; Lamers et al., 2002). In many countries, a significant part of peat mines are and will be left as seminatural wilderness areas and spontaneous re-vegetation is taking place (Lavoie et al., 2003; Girard et al., 2002). In recent years, creation of shallow lakes (1–2 m depth) in territories of cutaway peatlands is also considered as a valuable management activity. After the cessation of peat harvesting, different areas within a single peat field can vary considerably in terms of depth and type of the residual peat, the underlying soil type and drainage characteristics (McNally, 1998). Previous studies (Lally et al., 2008; Lundin et al., 2008; Higgins and Colleran, 2004) have indicated that, prior to the creation of cutaway lakes, considerable on-site management work should be carried out. Much of the residual peat substrate usually is removed from the cutaway to create a basin, exposing some of the underlying mineral sub-soil (Higgins and Colleran, 2004), but significant amounts of peat mass from highly decomposed peat layers may be left after major peat mining. Depending on the lake depth, size, aquatic chemistry, vegetation and other properties, the created lakes can be used for recreation purposes or can be important sites for wildlife, especially waterfowl conservation (Lamers et al., 2002).