TRINITY RIVER ALLUVIUM, A POTENTIAL MINOR AQUIFER IN TEXAS?

Groundwater resources in North Texas are taking on increasing importance as population grows and surface water resources reach capacity or are limited by drought. Subsurface resources are also limited, and preliminary groundwater availability models for major aquifers in the Metroplex predict water level declines of several hundred feet by 2050. In this context minor aquifers take on increasing importance, and one such aquifer is the Trinity River alluvial aquifer. This aquifer extends from McKinney southward beneath Lakes Lavon and Ray Hubbard and on to the Gulf Coast, and could potentially provide water to a number of cities such as Fairview.

The upper reaches of this aquifer lie beneath Wilson Creek, which runs through the Heard Natural Science Museum in McKinney and eventually feeds into Lake Lavon. Quaternary terrace and alluvial deposits fill a substantial paleovalley cut here by the ancestral East Fork of the Trinity River. Our study investigates aquifer composition, water level and major and trace element variability of samples taken from wells, ponds and streams at the Museum. Correlating these with data from earlier measurements will help us understand temporal (e.g. drought and wet period) changes in this groundwater-surface water system.

Initial investigations have found a shallow confined sandy-silt aquifer, possibly representing terrace deposits, and exhibiting moderate hydraulic conductivity (sufficient for domestic wells). The confining layer is a thick blackland clay soil. We expect that the aquifer becomes coarser and more productive downstream (more alluvium, less terrace material) and water quality is similar to the Brazos River alluvial aquifer. These results provide some indication that the Trinity River alluvial aquifer warrants further investigation, and may be a candidate for Minor aquifer status.