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New high‑resolution mapping shows complex structure and variable protection for the Muhammad Aquifer, researcher tells county board
Summary
Prairie Research Institute staff presented the first high‑resolution 3D mapping of the Muhammad Aquifer, finding variable sand/gravel (aquifer) and fine‑grain (confining) units, buried channels and areas where the confining layer is thin — details county officials said will inform the data‑center moratorium and future water‑management decisions.
Dr. Gilkkey of the Prairie Research Institute presented results April 23 showing high‑resolution 3‑D geophysical mapping of the Muhammad Aquifer that, the presenter said, provides greater detail than prior models of bedrock valley geometry and aquifer material distribution.
The presentation: the research used airborne electromagnetic surveys, resistivity transects, drilling and seismic ambient‑noise methods to map the top and internal composition of the bedrock valley that contains the aquifer. Dr. Gilkkey said the team identified distinct zones of sand and gravel (good aquifer material), fine‑grain clays (confining units) and carbonate layers, and located buried channel features that may act as additional shallow water resources.
Key findings and implications: the mapping shows the aquifer is not a single uniform container. In parts of the county the aquifer is thick and bounded by substantial confining units; in other areas the confining layer is thin or absent and shallow aquifers are hydraulically connected to deeper Muhammad Aquifer layers. That connectivity means shallow withdrawals or contamination in those areas are more likely to affect the deeper system, the presenter said. Dr. Gilkkey described the work as the "first ever high‑resolution mapping of the Muhammad Aquifer" and recommended integrating these results into groundwater flow models to better estimate available water and vulnerability.
County response and next steps: the presenter said the Illinois State Water Survey would need funds to integrate the data into groundwater‑flow models; Prairie Research Institute staff asked the board and partner counties to consider funding or technical collaboration to expand mapping coverage. Board members asked about monitoring and how contamination would be detected; Dr. Gilkkey said the State Water Survey conducts monitoring in wells and that integration into models would improve detection and planning.
Why this matters: the detailed geometry and connectivity information are precisely the kind of technical inputs county officials and the data‑center task force said they needed to assess water risk before permitting large, water‑intensive facilities. Several board members referenced the presentation during the moratorium debate; staff said the mapping will be provided to the task force and planning staff for ordinance drafting.
