Mining activity impacts on soil erodibility and reservoirs silting: Evaluation of mining decommissioning strategies

Abstract

This study focuses on the nexus between coal mining and water storage, analyzing the strategies to reduce the negative effects of exhausted/abandoned mining sites on catchments where water reservoirs are located.Sediment management represent a key point to promote sustainable water resources development and it is strictly connected with the proper management of land use change, especially in the areas devoted to mining activities. The presence of a reservoir represents a major challenge because these structures are threatened by the rapid loss of storage volume due to excessive sedimentation.The case of San Cipriano reservoir in central Italy represents an ideal set to explore the effects of mining on water storage because it is located at the outlet of a catchment strongly influenced by one of the most important lignite mine in central Italy. The Soil Water Assessment Tool (SWAT) is used to evaluate different scenarios of mine decommissioning, aiming at supporting the identification of the best strategies to avoid reservoir sedimentation. Two scenarios of environmental restoration of the mining area are evaluated. In the first case, the ongoing reforestation with native plants like oaks and deciduous trees is analyzed. In the second scenario the authors focus on the evaluation of a wider landscape restoration project (including reforestation and river bodies rehabilitation) recently drafted by local institutions.The results provide a quantitative evaluation of the effectiveness of the proposed strategies in reducing the impacts of existing mining sites from a hydrological perspective. In particular, the analyzed scenarios show that afforestation and river restoration lead to a strong reduction of sediment yield while downward trend occurred for water yield.