INTERACTIONS BETWEEN THE MIDDLE SEGMENT OF THE BRAZOS RIVER ALLUVIUM AQUIFER AND THE UNDERLYING BEDROCK AQUIFERS

Data analysis suggests that the middle segment of the Brazos River Alluvium Aquifer (BRAA) interacts with the underlying bedrock aquifers. Previous research has shown that water flows both in and out of the bedrock aquifers in different locations, and that overall, water flows from the bedrock to the alluvium. Well logs from the Texas Water Development Board (TWDB) containing information on lithology, hydraulic head, and water quality were analyzed for this project. Data were also gathered from paired alluvial and bedrock aquifer wells. Analysis was completed using ArcGIS Pro (version 3.2), Geochemist's Workbench Community Edition 17.0 (64 bit), and Microsoft Excel (version 2311). Hydraulic head was compared between pairs of alluvial and bedrock wells to determine the hydraulic gradient. Water chemistry of these well pairs were also compared. Both hydraulic head and water chemistry were analyzed over a period of several years to see if patterns in the alluvium matched patterns in the bedrock. The hydraulic gradient suggests that water flows from the bedrock to the alluvium in most areas. Data suggest that flow from the bedrock into the alluvium does not appear to impact the water quality in the alluvium.