An Integrative Approach for Understanding Groundwater Processes Using Multi-Scalar Data in a Shallow Karst Aquifer

In the Northern Segment of the Edwards Balcones Fault Zone Aquifer in Central Texas, managing groundwater-surface water interactions has been challenging during an epic drought, but has never been more pertinent. This karst aquifer is the source of local drinking water, spring flow is a desired future condition of the local groundwater conservation district, and an endemic salamander that inhabits the springs is a candidate for the endangered species list. Knowledge of groundwater recharge and its relationship to spring discharge are important for managing both water supply and critical habitat. However, these process relationships are difficult to characterize and quantify due to complex patterns of anisotropy and heterogeneity.

A study employing physical and chemical sampling methods and analysis of high-resolution topographic data is ongoing in the Northern Segment. Integration of both field-collected and remotely-sensed data increased understanding of aquifer processes. In the initial phase of the study, several physical and chemical sampling methods were applied to the Salado Springs area of the Northern Segment. Water levels from wells were measured to create a synoptic potentiometric surface under low-flow conditions (drought). The synoptic surface was compared to historical data to better understand aquifer change over a large interval of several years. Water level, temperature, and specific conductance were monitored over small sampling intervals using a multi-parameter datalogger revealing responses not visible at larger intervals. These data were related to precipitation data during recharge events, giving insight to aquifer responses. Dye tracing conducted in a key location confirmed old flowpaths and revealed flowpaths near springs discharging along Salado Creek. Utilizing multi-scalar physical and chemical methods resulted in different but complementary data providing new insights into groundwater recharge, storage, and flowpaths in this important Central Texas aquifer.