What a Declining Water Table Means for a Residential Well Pump
Depth is what a pump actually works against
A submersible pump has to lift water from whatever depth it currently sits at. As that depth increases, the pump runs longer per cycle and works harder against a longer column of water, both of which shorten a motor's working life. This is a mechanical fact independent of how fast the decline is, a county in this site's "mild" decline band still sees it, just more slowly than one in "severe." The exact bands come from this dataset's own distribution, see the methodology guide.
What this site can and cannot tell a well owner
This site reports a county's fitted trend from the nearest qualifying USGS well, not a reading from any individual property's own well. A property's actual depth to water can differ from the county figure. A well log or a direct measurement from a licensed well contractor is the only way to know a specific well's own numbers, especially in a county with no qualifying well at all, see the no-data guide for what that gap does and doesn't mean.
Three counties where this risk is live
Jones County, IA, McDonald County, MO, Stevens County, KS are among the counties where a declining water table is a real, measured trend rather than a general worry, each tracked by its own USGS well. A well owner in any of them is the person this guide is written for.