Article woo aside, underground water is not impossible to measure. Min well depth (or depth of dry wells) is a straightforward way to measure the aquifer level

Article woo aside, underground water is not impossible to measure. Min well depth (or depth of dry wells) is a straightforward way to measure the aquifer level for a small area. It doesn’t tell you much but it tells you something. Combine with your neighbors taking the same measurement over time and you have a good data set. That is before you get to things like ‘geology’ which are known factors shaping underground water supplies. Further, if water goes into a pit, you can measure or estimate how much is going in. If you can measure the shape of the pit you know how much is there. If you know surface area at a given level and temp/environmental conditions you can estimate evaporation. So you can say: X vol went in, Y evaporated, and Z is how much we now think is ground water based on current depth and evaporation (excluding animals and humans drinking). It is much harder to associate the pit activity with a given well and obviously the scale here may be below the precision of any of the estimators.