Abstract: Cover systems consist of soil layers with different properties and different functions.They are exposed to the atmosphere and to vegetation.The water content of the soils varies with seasons and weather conditions.In winter,the degree of saturation of the soils increases,and in summer the water content is reduced while the matric suction increases.If the matric suction in the compacted clay layer exceeds a limiting value,desiccation cracks occur,and the sealing function is impeded.In order to examine the performance of mineral cover systems,two large scale test fields were installed with different thickness of the restoration profile.Preliminary results of these investigations were presented including data of water flow,matric suction and soil temperature.The role of the restoration profile for the water balance of the cover systems was focussed on.