REVISING THE CONCEPTUAL MODEL FOR THE EDWARDS AQUIFER/TRINITY AQUIFER INTERFACE

Conventional conceptual models of the Edwards Aquifer/Trinity Aquifer interface characterize the Trinity Aquifer as a relatively poor aquifer which provides allogenic recharge to the highly permeable Edwards Aquifer. Recent investigations, however, indicate the hydraulic relationship between these two regional aquifers is more complex. Water-budget analyses predicated on these studies indicate that the quantity of water recharged to the Edwards Aquifer from the Trinity Aquifer exceeds that implied by the conventional conceptual recharge models. This finding implies that the Trinity Aquifer captures water from a broader expanse than boundaries indicated by surface water divides. The mechanisms that convey recharge from the Trinity Aquifer to the Edwards Aquifer are not simply surface flow from the contributing zone (i.e., Trinity Aquifer) to the Edwards Aquifer recharge zone where it infiltrates the subsurface. Actual conveyance of recharge has a larger subsurface component associated with river and stream channels. The technical basis for a revised conceptualization of the hydraulic relationship between the Edwards Aquifer and Trinity Aquifer is summarized in this presentation.