Allegheny County, PA Water Table Trend
Allegheny County, PA: what the water table is actually doing
Allegheny County's long-term well puts the trend at 0.3 ft per decade, holding roughly steady, based on 233 measurements since 1967.
One well stands in for Allegheny County's whole aquifer here, the honest simplification every page on this site carries.
What the well actually measured
The most recent reading put water 7.1 ft below land surface. Readings span 1967-06-01 to 2026-07-23, 233 measurements from USGS well USGS-403734080063001 (Ag 700 Allegheny County Observation Well), part of the National Water Information System. The qualifying bar and the OLS fit behind this trend are documented in the methodology guide.
Where Allegheny County ranks
Of the 1,449 US counties with a usable trend, Allegheny County ranks 453rd from fastest-rising to fastest-declining, 1 is the fastest-rising water table measured, 1449 the fastest-declining. About 1,231,814 people live in Allegheny County, Pennsylvania. See the fastest-moving counties guide for how Allegheny County stacks up against the most extreme cases nationally.
A dropping table says nothing about water quality
Whether Allegheny County's water table is rising or falling is independent of what's actually in the water. Depletion can concentrate naturally-occurring minerals, so it's worth checking directly with a water test rather than assuming a depth trend says anything about quality.