Spring 2009 potentiometric map of the Middle Trinity Aquifer in Groundwater Management Area 9, central Texas

Abstract

The Trinity Aquifer is the primary groundwater source for a variety of needs throughout the Texas Hill Country. Groundwater Management Area 9 (GMA-9) is composed of nine Groundwater Conservation Districts (GCDs) within the Texas Hill Country that are tasked with managing groundwater resources. Recent State law requires Districts to periodically meet to discuss the future availability of groundwater within the aquifers of GMA-9. Increasing water-supply demands have raised concerns about the availability of groundwater in the Texas Hill Country. In particular, the Middle Trinity Aquifer is the primary aquifer for water-supply needs. At an early 2009 GMA-9 meeting, it was discussed that a potentiometric (water level) map of the Middle Trinity Aquifer constructed during the ongoing drought would provide useful information. All GCDs in the GMA agreed to participate and send the authors water-level data collected from the Middle Trinity Aquifer during the Spring of 2009. Groundwater levels and potentiometric surface maps provide critical information about the hydrologic relationships of recharge, discharge, and storage within an aquifer, and the direction of groundwater flow. This report contains historic potentiometric maps and a new Spring 2009 potentiometric map representing moderate drought conditions within the Middle Trinity Aquifer of the central Texas Hill Country. The purpose of this report is to provide a foundation of information and data for future hydrogeologic investigations and evaluations of water resources. These maps and data will be useful for computer modeling, sustainable yield determinations, and resource protection.