Grant County, SD Water Table Trend
Grant County, SD: what the water table is actually doing
Grant County's long-term well puts the trend at 2.8 ft per decade, rising, getting shallower over time, based on 373 measurements since 1979.
This is one representative well, not a county-wide survey, the same grain limit every page here discloses.
Grant County's source well, in detail
Depth to water at the last reading was 25.8 ft below land surface. Readings span 1979-10-25 to 2026-10-07, 373 measurements from USGS well USGS-451848096363501 (121n47w06cccc (Milbank Well)), part of the National Water Information System. The qualifying bar and the OLS fit behind this trend are documented in the methodology guide.
How Grant County compares nationally
Grant County sits at rank 100th 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. Grant County, South Dakota is home to about 7,618 people. See the fastest-moving counties guide for how Grant 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 Grant 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.