Delineating changes in vertical hydrogeologic connectivity in the Silurian-Devonian Aquifer using transient high resolution head profiles

Water scarcity issues are likely to increase in the future because of increasing human development and climate change. Groundwater is a vital source of water around the world, and just like surficial water sources, groundwater is prone to issues such as depletion and contamination. For this reason, understanding local groundwater systems has always and will always be important for those managing water supplies. The main tool water managers use to determine how to implement new wells and pumping operations are groundwater models. These models are divided into hydrostratigraphic units (HSUs), geologic layers with similar hydrogeologic properties. HSUs are usually classified at a coarse resolution which is usually sufficient for identifying large scale water availability; however, coarse delineation is insufficient for groundwater contaminant transport models which are vital for cleaning up contaminated sites and ensuring water produced by wells is safe to drink.

The Silurian-Devonian aquifer system of eastern Iowa is a regionally important source of water, that like many systems, has not had HSUs delineated at a high resolution. While traditional methods have been used in the past to broadly improve the understanding of this system, the work performed for this thesis utilizes novel methods that allow for several high-resolution water level measurements to be made throughout the span of a single borehole. Using relationships between the measured water levels as well as the aquifer’s response to external stresses such as atmospheric pressure changes, this approach allowed for high resolution delineation of several different zones within the system.