Comparing monitoring events

Before comparison, verify units, vertical datum, measurement reference, water-bearing unit, screen-selection rule, and event timing. ps_head_change() returns paired-well measured changes separately from the modeled B-minus-A surface difference and accounts for changing membership. Modeled head change is not storage, depletion, recharge, or volumetric change.

change <- ps_head_change(event_a, event_b, pair_by="well_id",
                         event_a_time=t1, event_b_time=t2, method="TPS")