Bryan Times, Oct. 16, 2018 (Report by Kevin M. Maynard, Director of Utilities, Glaciers created the Michindoh aquifer) Williams County’s geology was permanently altered by a number of glaciers that once covered the area, the last of which occurred approximately 13,000 years ago. These glaciers pushed through Williams County like huge bulldozers, scraping up everything in their paths.
As the glaciers advanced and retreated, they deposited materials on top of local bedrock, leaving a diverse underground mixture of discontinuous water-bearing sand and gravel lenses and layers topped with clay. Glacial materials deposited on area bedrock range in depth from approximately 320 feet in northwestern Williams County to less than 80 feet in Springfield Township.
Local clay deposits make it difficult for rain and snow melt to percolate into the so-called “Michindoh aquifer” below. The United States Geological Survey (USGS) estimates approximately one-half of Williams County’s groundwater enters the aquifer in the “chain of lakes” region running roughly from Angola, Indiana, to Hillsdale, Michigan. County bedrock and land surface elevations descend from northwest to southeast, causing groundwater to generally flow in that direction.
As the land surface descends toward Bryan, groundwater attempts to “seek its own level” or in other words rise to the same elevation that it entered the aquifer. However, in the same manner that clay restricts rainwater and snow melt from percolating into the aquifer, it also impedes this upward water movement, creating artesian pressure. When wells are drilled through the clay layer, artesian pressure causes water to rise in the well casings. For example, Bryan municipal water system wells are 120 to 147 feet deep, but water rises in the well casings to approximately 30 to 35 feet below the ground surface due to artesian pressure.
During a three-year USGS study of Williams County groundwater resources in the 1980s, water levels in 87 wells across the county were monitored for two years. Water levels were generally less than 30 feet below land surface elevation. No water levels greater than 75 feet below the land surface were observed during the study.
In some cases, such as at the former Fountain Grove Cemetery sexton’s residence on South Main Street, flowing artesian wells were identified. Water levels in most of the USGS study wells fluctuated less than four feet over a two-year monitoring period.
As mentioned earlier, approximately one-half of Michindoh aquifer recharge flows into Williams County from Michigan and Indiana. Additional aquifer recharge results from rain and snow that falls on Williams County. However, of an average 34 inches per year o local precipitation, the USGS estimates that only 2-8 inches ends up recharging the Michindoh aquifer.
With the exception of southeastern Williams County, local well yields can exceed 500 gallons per minute (gpm). The City of Bryan has several municipal wells capable of producing 1,000 gpm or more.
Local groundwater is generally suitable for most uses, although it is very hard and high in iron. Forty-eight Williams County wells were sampled for chemical contamination as part of the USGS 1980s groundwater resources study, with no problem areas identified at that time.