Regional Impact of Uranium Mining on Piezometric Surfaces in a Multi-layered Water-bearing System, Bohemian Cretaceous Basin, Czech Republic
Abstract
The former mining of uranium in Cenomanian sandstone sediments has had a tremendous impact on natural groundwater flow in a multilayered water-bearing system within both the Bohemian Cretaceous Basin and the Czech Republic. Newly created graphs and maps of piezometric surfaces provide insight into the dynamics of the basin's water-bearing system and give an idea of long-term groundwater heads and flow directions in the area, despite the fact that this study was simply an interpolation of monitoring data.
Maps and grids of piezometric surfaces were used to calibrate hydraulic models. The piezometric surface of the Cenomanian aquifer in the StraA 3/4 block was lowered by 170 m by underground uranium mining, with the affected area extending more than 50 km along the regional flow direction.
The extent of the piezometric surface affected (600-700 km(2)) is much larger than the area directly affected by the chemicals that were used for acid in-situ leaching (24-27 km(2)). Other aquifers, especially the Turonian aquifer, which is widely used as a water supply, have not been seriously affected.
At the current rate of flooding of the residual depression, the piezometric surface may reach the pre-mining state within several decades. The possibility of returning to the natural groundwater regime in the in-situ leaching area and its forefield depends on the remediation technology that will be used at those sites in the future.
Such an extensive intervention into the groundwater regime has to be seen in context of its long-term development. Based on the recorded far-reaching influence of mine dewatering and flooding on the piezometric surface of the Cenomanian aquifer towards the southwest, it is appropriate to refer to the entire Boleslav-Mlnik water-bearing system adjacent to the StA (TM) edohoA (TM) i fault zone (from the infiltration area at LuA 3/4 ice fault to the drainage area in the Labe river valley) as the StraA 3/4 block.