Efficiency of Vegetation Types on Rainwater Infiltration of a Hypothetical Potash Tailings Pile – Results and Recommendations from a Modelling Study

The extraction of potassium salts produces large quantities of solid residues, consisting primarily of sodium chloride and, to a lesser extent, magnesium sulfate, magnesium chloride, and insoluble clay minerals. These saline residues have been deposited on the Earth's surface, forming potash tailings piles that can reach heights of up to 200 meters. In Central Germany, numerous potash waste piles characterize the landscape and are particularly noticeable due to their striking appearance and the usually complete absence of vegetation. When rainwater comes into contact with saline residues, sodium chloride in particular can be dissolved and mobilized. This saline seepage can penetrate the subsurface and reach the groundwater. This poses a risk of salinization of the surrounding aquifers and the impairment of surface waters and adjacent ecosystems. Soil coverings with protective vegetation are a potential measure to reduce contact between rainwater and saline residues. The aim of this research is to assess the efficiency of different vegetation types in order to minimize the negative impact of infiltrated rainwater on groundwater. This is investigated using the numerical simulation software Advanced Terrestrial Simulator (ATS), which enables the coupling of surface and subsurface flow as well as the modeling of evapotranspiration. Results indicate that care must be taken in the definition of the free-outflow boundary condition of the drainage layers. Results also show that vegetation types with a deep root zone and a high Leaf Area Index are most suitable as efficient vegetation cover.