Passage: Groundwater can be thought of in the same terms as surface water: inputs, outputs and storage.  The critical difference is that due to its slow rate of turnover, groundwater storage is generally much larger (in volume) compared to inputs than it is for surface water. This difference makes it easy for humans to use groundwater unsustainably for a long time without severe consequences.  Nevertheless, over the long term the average rate of seepage above a groundwater source is the upper bound for average consumption of water from that source.

Question: Since groundwater can be stored for a long time this makes it easy for who to use it?
humans