LaSalle County, IL Water Table Trend
LaSalle County, IL: what the water table is actually doing
LaSalle County's long-term well puts the trend at 1.3 ft per decade, rising, getting shallower over time, based on 14 measurements since 1999.
This is one representative well, not a county-wide survey, the same grain limit every page here discloses.
LaSalle County's source well, in detail
Depth to water at the last reading was 16.1 ft below land surface. Readings span 1999-07-12 to 2026-06-01, 14 measurements from USGS well USGS-413141088402401 (35n5e-9.7h), part of the National Water Information System. The qualifying bar and the OLS fit behind this trend are documented in the methodology guide.
How LaSalle County compares nationally
LaSalle County sits at rank 190th of 1,449 ranked counties, ordered rising-to-declining, so a low number means a rising water table and a high one means fast decline. LaSalle County, Illinois is home to about 108,390 people. See the fastest-moving counties guide for how LaSalle County stacks up against the most extreme cases nationally.
Depth and quality are separate questions
This page answers a depth question, not a quality one. A well in LaSalle County can be stable in depth and still worth testing for quality, or declining and still test clean, the two are measured separately, and only a direct test settles the second one.