The Leyden mine artificial aquifer storage and recovery system was originally monitored by time-lapse gravity from 2004 to 2005 during the water injection period. We now continue that survey seven years later to assess the effectiveness of water storage. In order to do so we must remove sources of noise associated with a long term time-lapse gravity survey in an area with large anthropogenic effects. Missing time-lapse stations were located and reoccupied by using a combination of differential GPS and satellite image referencing. To correct for effects due to a surface quarry and landfill, surface change corrections are calculated by using digital elevation models from different time periods, analogous to a time-lapse terrain correction. After removing these effects, quantitative analyses by means of binary inversion and surface inversion are used to compare to previous work and map the current distribution of water. Comparisons based on surface inversions suggest that no water has left the system, but rather the water has redistributed itself slightly throughout the mine.
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