There are two different aftercare strategies implemented by the LMBV to prevent the natural acidification of post-mining lakes in Central Germany: The discharge of alkaline river water if applicable (Lake Zwenkau) and the location-independent ship-based liming (Lake Hain and Lake Störmthal).

After German Reunification in 1990, the LMBV is responsible for decommissioning and rehabilitation of no longer profitable open-cast lignite mines of the GDR. This includes flooding and aftercare of the resulting post-mining lakes in Central Germany, most noteworthy Lake Zwenkau, Lake Hain and Lake Störmthal. After decommissioning of the LMBV flooding pipeline at the end of 2018, the LMBV is forced to use alternative aftercare strategies to ensure the water quality of post-mining lakes. At Lake Zwenkau an inlet of alkaline river water of the Weiße Elster river is available. Therefore, aftercare of the water body´s quality can be realized primarily by using this alkaline river water. If necessary, the ship-based liming is also an additional option for application on short notice.Lake Hain and Lake Störmthal do not feature any noteworthy inlets of external surface water, leaving limestone treatment by ship as the only feasibly option for aftercare treatment purposes. Without aftercare treatment, due to Oxidization of iron-sulfate-minerals (pyrite) in corresponding dumps, the pH values would decrease and cause high iron and aluminium concentrations in the groundwater and ultimately in the Lake´s water bodies. According to the post-mining lake´s legal plan approval decisions (PAD), for environmental reasons the water bodies and its discharge are required feature a pH-value between 6.0 and 8.0.

Every lake has a different alkalinity demand, based on the individual dump´s geology and groundwater flow direction. The actual amount of limestone input for aftercare is determined based on the continual Lake monitoring data. Over the last 5 years (2019 – 2023) no ship-based liming was necessary at Lake Zwenkau due to sufficient alkaline river Water discharge from the Weiße Elster River, meeting the annual alkalinity demand of about 40 M mol_Alk. Over the same period, Lake Störmthal (estimated alkalinity demand about 22 M mol_Alk/a) required aftercare treatment with about 7,500 tonnes of limestone, and Lake Hain (estimated alkalinity demand about 12 M mol_Alk/a) 2,900 tonnes respectively.

By applying the discharge of alkaline river water and the location-independent ship-based liming, the LMBV has two distinct aftercare strategies to counter natural acidification and therefore ensure the water quality of post-mining lakes in Central Germany.

Geospatial technologies have been shown to be a critical tool within the mining and reclamation sector to monitor and analyze changes on the landscape. One of the newest ways to collect high temporal and spatial resolution data is with unmanned aerial vehicles (UAVs) or drones. Our study highlights the available benefits of using UAV imagery to map and analyze legacy issues with former mine lands. The data that can now be collected over hundreds of acres provides site level modeling to plan for both the reclamation and future development of former mine lands.

Our approach is unique in the capture of engineering-level site measurements using a fixed-wing UAV at a former mine land site in the southern coalfields of WV. The information once collected and processed included an orthophoto, a digital surface model (DSM), and a digital elevation model (DEM) for each of the flights. The ability to have this information in a timely high resolution (4cm) manner provided for a quick analysis of disturbed areas. Models could be built of overland drainage and topographic constraints to help in the planning of development options

We found the UAV data collection approach with a specific fixed wing unit allowed a small crew to effectively and efficiently capture information that resulted in a major time and cost savings compared to tradition field sampling and analysis. We were able to construct bare earth as well as vegetation height models to help us identify sites at the former mine land where development options could be compared with costs associate with cut/fill and other volumetric analysis needed for access and development. The detail of the surface model provided a way to track overland flow across the landscape and account for drainage paths. The high-resolution imagery overlaid on the surface models allowed for development renditions in a landscape context. These site plans remove uncertainty in the construction process for post mining development options.

The remediation of the legacies of uranium mining in eastern Germany has been carried out by WISMUT since 1991 and is accompanied by an environmental monitoring. The status of remediation after approximately 30 years varies. While the majority of the waste rock dumps have already been remediated and are undergoing aftercare, work on the industrial tailings ponds has not yet been completed. A long-term task remains the regulation of flooded mines and the water treatment at several sites.

Environmental monitoring includes all compartments, as surface and groundwater, air and solids. Monitoring of particulate matter as a preliminary stage to sediment takes place particularly in the area of discharges from the water treatment plants. However, other point and diffuse inputs are also recorded, which ultimately characterize the respective remediation site. For the investigation of suspended matter, sediment traps have been installed. Key analytical parameters along the water and sediment path are uranium and radium-226. In addition to this, arsenic, iron, manganese, nickel, zinc and TOC are of interest depending on the specific sites. Over the 20-year observation period, the quality of these suspended solids is well described. The assessment of river quality is guided by both German and European (EU WFD) regulations, which for some elements (e.g. arsenic) focus exclusively on the quality of suspended solids or sediments.

The water treatment plants run by WISMUT prevent pollutants from entering the respective river section, which is also of trans-regional importance due to the sediment transport along the rivers. Thereby, water management thus also represents a sediment management.

All remediation sites of WISMUT are located in the catchment area of the Elbe, which has its source in the Czech Republic, then flows through eastern and northern Germany into the North Sea. The low mountain ranges are characterized by high rock diversity, polymetallic deposits and mining. This already leads to elevated geogenic background concentrations in water and sediments in the tributaries. The pollution situation of the Elbe and its tributaries has been substantially improved by a variety of measures since the beginning of the 1990s until today. Due to the transport of pollutants along the watercourses and the sediment property as a long-term memory of a river, measures at the source (as at WISMUT) are in principle of particular interest and will be demonstrated with case studies.