Findings from flooding residual pits remaining after coal mining in the Czech Republic

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F25173154%3A_____%2F16%3AN0000035" target="_blank" >RIV/25173154:_____/16:N0000035 - isvavai.cz</a>

Result on the web

<a href="https://www.imwa.info/docs/imwa_2016/IMWA2016_Prikryl_131.pdf" target="_blank" >https://www.imwa.info/docs/imwa_2016/IMWA2016_Prikryl_131.pdf</a>

DOI - Digital Object Identifier

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Result language

angličtina

Original language name

Findings from flooding residual pits remaining after coal mining in the Czech Republic

Original language description

he work summarizes more than twenty years of experience in designing reservoirs in residual pits remaining after mining of brown coal in the Czech Republic, monitoring their flooding and development of lakes after filling. There are currently 3 artificial lakes in residual pits with a water surface of 225 to 496 hectares. In the future there will be another 5 lakes covering area in the range from 390 to 1,300 hectares. The beginning of their flooding is expected mostly after year 2035. Due to complete lack of natural lakes in the Czech Republic, the main expected use of these artificial lakes is recreation, including sport fishing. Rehabilitation projects of mined areas are processed for many decades prior to the termination of mining. This planning gives the possibility to optimize the morphology of the residual pit with minimal cost. Subsequently, studies have repeatedly supplemented and corrected. However coal mining is currently associated with the risk of early termination of mining, when the residual pit does not have the optimal morphology. This also concerns all residual pits with regulated flooding in the Czech Republic. The stabilization of residual pit slopes is associated with the greatest cost and problems, which are mainly the consequences of water saturation of soils that had been drained for decades. Especially expensive is the fortification of shoreline at the final water level. Abrasion during lake filling is confined to a strip not exceeding 2 m around the perimeter surface and does not affect the overall stability of the slopes. For flooding the preferred option is water with the least contamination. There are enough data on the quantity and quality of water selected to flood the residual pits. On the contrary little data are available about the quantity and quality of water flowing from the slopes of the quarry. It is crucial for the development of the water quality of lakes in the period after of their filling. Water quality is not a problem in the Czech conditions. The resulting pH of lake water in all cases is slightly alkaline. This, together with good oxygenation of the water leads to a drop in metal concentrations below the limits for surface water even during filling. Nowhere was found significant contamination by chemicals or bacterial contamination. Trophic state is adapted to the amount of inflowing nutrients and depth of reservoirs within a few months. Residues of mine water on the bottom of the pit cause short-term or long-term meromictic state. In one lake is formed near the bottom anaerobic state, which on the end of November, affects about one third of the lake area. The concentration and species composition of plankton, benthos and fish is strongly influenced by very low water trophy. Problems with cyanobacteria water blooms were not observed and this situation is sustainable. Submerged vegetation develops rapidly and large reservoirs are attractive for water birds. There is no clear definitive future owner of the lakes due to fears of the high costs associated with the maintenance of the lakes.

Czech name

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Czech description

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Type

D - Article in proceedings

CEP classification

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OECD FORD branch

10503 - Water resources

Project

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Continuities

N - Vyzkumna aktivita podporovana z neverejnych zdroju

Publication year

2016

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Article name in the collection

IMWA 2016 Annual Conference Mining meets Water - Conflicts and Solution

ISBN

978-3-86012-533-5

ISSN

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e-ISSN

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Number of pages

8

Pages from-to

201-208

Publisher name

TU BERGAKADEMIE FREIBERG, INST MINING & SPECIAL CIVIL ENG

Place of publication

Leipzig

Event location

Leipzig, Germany

Event date

Jul 11, 2016

Type of event by nationality

WRD - Celosvětová akce

UT code for WoS article

000402663400036