SURFACE WATER AND GROUNDWATER INTERACTIONS IN THE MIDDLE SEGMENT OF THE BRAZOS RIVER ALLUVIUM AQUIFER

The Brazos River Alluvium Aquifer (BRAA) is an important source of irrigation and agricultural water supply for farmers and ranchers in Central Texas. The interactions between the Brazos River and the BRAA that it overlies are poorly understood and often overgeneralized. This study seeks to improve understanding of the interactions in the middle segment of the Brazos Valley (defined as the section in Brazos, Burleson, Milam, and Robertson Counties). While regional modeling has been guided by the Texas Water Development Board (TWDB), the models fail to account for many spatial and temporal heterogeneities, seasonal variations, and river-aquifer interactions at the cost of model complexity and computation time. This study uses both historical data from the TWDB’s Groundwater Database (GWDB) and original data to better define hydrogeologic gradients, chemical composition, and flow variation in the middle segment of the BRAA. Preliminary results show a generalized hydrogeologic gradient encouraging flow from the BRAA to the Brazos River with limited temporary reversals during periods of increased river discharge and higher channel water levels. Further research into the chemical composition distinction among the different waters and more in-depth field work refining hypotheses proposed by preliminary data will be conducted.