Hydrological Mine Reclamations in the Anthropogenically Affected Landscape of North Bohemia

Abstract

The surface mining of brown coal has long burdened the landscape of the northern part of the Czech Republic (the Most Basin). A total of 31.07 million tons of coal were mined in this area in 2016, and since the year 2005, 432.7 million tons have been mined there so far. The area is disturbed by surface quarries, external spoil tips and related anthropogenic interventions in the territory and its vegetation. Most of these interventions resulted in the removal of vegetation and were connected with the distortion of the natural dynamics of surface water and groundwater. Short water cycles caused by natural succession were disturbed and with them the conditions for the healthy functioning of the basin area ecosystems. Hydrological mine reclamations are one way of using the residual quarry after the end of coal mining. They are an essential part of a newly formed landscape. They have a technical, ecological and also aesthetic function. Their presence increases ecosystem diversity and creates significant biocenters and biocorridors. Technical measures (ditches, terraces, retention tanks, detention basins) for hydrological stabilization must be implemented within the reclaimed sites. Significant hydrological mine reclamations of local character are usually located where the surface mining has taken place, but depressions that are being developed during spoil tip creation could be spaces for small aquatic areas and wetlands. The flooding of the remaining quarries was finished in case of smaller mining areas. Examples are the Benedikt quarry and the Vrbenský quarry where the artificial Lake Matylda is currently located. The first, more massive artificial lake was made by flooding the Chabařovice quarry, which was filled with water during the period from 2001 to 2010. This 252 ha lake is now called Milada and is used for recreational purposes. Another large hydrological mine reclamation was created by flooding the Most quarry, where the filling was completed in 2014. This lake is 316 ha in size, but the final terrain works are still to be completed, so the lake is not yet accessible to the public. This form of mine reclamation will become more important in the future. There are planned hydrological mine reclamations for the Vršany and Bílina quarries and the ČSA (Czechoslovak Army) quarry, which will be 1259 ha in size after the flooding. The assumption is that these newly created and deep lakes will be permanently oligotrophic with high water quality. The realization of hydrological mine reclamation is connected with a series of tasks and measures. It is necessary to solve the area’s geomechanical and hydrogeological conditions to avoid slippages and to ensure slope stability. The coal deposit, lake bed, and permeable horizons must also be sealed before flooding the quarry. The appropriate technical and biological measures ensure the stability of the shoreline. Final work consists of monitoring the water quality and the realization of other measures within the conditions issued for implementation. The mine reclamation has been conceptually designed for decades to create a landscape with a proportional share of forests, agriculturally usable areas, aquatic areas and areas suitable for nature and various types of construction. The resulting landscape is then ecologically productive, economically active and perfectly habitable, while at the same time usable for local and regional recreation. This chapter deals with the techniques used in the hydrological mine reclamations, focusing on individual examples in the monitoring area. It also describes the importance of newly created aquatic areas for the aquatic regimen of an anthropogenically affected landscape.