Discrepancies on the spilled volume in the Aznalcóllar mine disaster

Abstract

The failure of the pond that stored the tailing of the mining activity of Aznalcóllar (1998) supposed one of the most catastrophic mine disasters ever worldwide. More than 400 scientific publications, including two special issues and two reviews, attempt to clarify the causes and the environmental consequences of the spill. However, some hydraulic aspects were analysed in less detail, and nowadays several uncertainties and inconsistencies still persist. The spilled volume was officially determined to be 4.5 hm 3 , and later on increased up to 6 hm 3 . Despite that, in the literature this value ranges from 0.45 to 10.32 hm 3 , being increased up to 14.4 hm 3 from data inferred from rating curves and the registered hydrograph. Additionally, the volume recovered during the restoration activities is also uncertain, ranging from 4.7 to 10 hm 3 . Differences between the spilled and the recovered volume can be due to the natural hydrological processes. To clarify that, this paper firstly conducts a state-of-the-art review of the spilled volume of the mine disaster, and then new data is introduced and analysed aiming to get some light in this essential hydraulic parameter. To that end, photointerpretation and digital terrain analysis techniques were applied to determine the volume that could potentially be spilled, and then unpublished data of the mean discharge registered at EA90 gauge station was analysed to estimate the volume spilled. The most important findings reveal that the spill could have had a volume around 11.5 hm 3 , twice the most referenced values in the literature.