Helping transform abandoned mining pits into a lake district

With the right strategies and tools, abandoned mining pits can be turned from lifeless landscapes into prosperous manmade lake districts. This is what has been done in Eastern Germany, where we provided accurate analyses and appropriate strategies for creating a new pit lake.

Large parts of Southern Brandenburg and Saxony in Eastern Germany are characterised by enormous industrial mining zones, where lignite has been mined and used for electricity generation. Although mining activities are still on-going and three large power stations continue to produce electricity, much of the industrial mining activities are planned to be phased out by 2015.

A number of old pits left behind by the mining process have already been transformed into a new landscape, creating a massive new lake district never before seen in this region. In connection with the development of a new pit lake (Cottbus See) with a surface area of approximately 19 km², Vattenfall Europe Mining AG contacted us to optimise the mine closure plan through accelerated flooding of the pit lakes.

To do this, we used integrated groundwater and surface water modelling. We based our studies on the following modelling components:

• a 3D FEFLOW groundwater model
• a MIKE 11 surface water model to describe different options for the outflow to the river Spree
• a WBalMo water and allocation model to identify long-term and optimal water allocations

With our comprehensive modelling studies, we helped in:

• reliable prediction of river flows that could be sustainably diverted into the pit
• reduction of pit flooding time frame by seven years from the original mine closure plan