Cook County, IL Water Table Trend
Is the water table dropping in Cook County, IL?
Cook County's representative monitoring well shows depth to water declining faster than most declining counties, a fitted trend of 6.7 ft per decade over 53 years of readings.
This is one representative well, not a county-wide survey, the same grain limit every page here discloses.
Cook County's source well, in detail
Depth to water at the last reading was 589 ft below land surface. Readings span 1966-08-24 to 2019-07-15, 11 measurements from USGS well USGS-414827087544001 (38n12e- 6.6b1), part of the National Water Information System. The qualifying bar and the OLS fit behind this trend are documented in the methodology guide.
How Cook County compares nationally
Cook County sits at rank 1348th 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. Cook County, Illinois is home to about 5,182,617 people. See the fastest-moving counties guide for how Cook County stacks up against the most extreme cases nationally.
If you own a well in Cook County
A dropping water table means a residential pump has to reach deeper and work harder, which shortens its life. In Cook County, that trend is real, not assumed: 6.7 ft per decade over 53 years.
Depth and quality are separate questions
This page answers a depth question, not a quality one. A well in Cook 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.