Sully County, SD Water Table Trend
The nearest real water-table reading to Sully County, SD
The closest qualifying well to Sully County is 49 miles away in Walworth County, SD, where the trend runs rising, getting shallower over time.
Sully County itself has no monitoring well with enough history to call its own trend, so treat this as a regional estimate, not Sully County's own number. If you own a well here, comparing your own depth log against this regional figure is worth doing before assuming either way. See Walworth County, SD's full page. See the no-data guide for why a county this close to a qualifying well still doesn't get its own number.
Sully County, South Dakota in brief
About 1,468 people live across Sully County's 1,007 square miles, in South Dakota. USGS's National Groundwater Monitoring Network covers 1,449 of 3,222 US counties (45%) today; Sully County isn't one of them yet, see the methodology guide for the exact qualifying bar.