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Native Plant Society of Texas

San Antonio Chapter

The Edwards Aquifer – The Geology, Hydrology, and Ecology of this Unique Aquifer System

image of bridge over a clear running stream

May 27, 2025 – 7:00pm
Arrive at 6:30pm to share or find native plants at the Plants x Donation table.

This will be a “hybrid” meeting, attend in-person or online.

  • In person: The Gathering Center at the Urban Ecology Center at Phil Hardberger Park, 8400 NW Military Hwy
  • Online: Please register in advance to attend via Zoom.

Presentation by Brent Doty, P.G., Research Manager, Edwards Aquifer Authority
The Edwards Aquifer – The Geology, Hydrology, and Ecology of this Unique Aquifer System

The Edwards Balcones Fault Zone Aquifer is one of the most prolific karst aquifers in the world. Brent will discuss the geologic, hydrologic, and ecological characteristics of the Aquifer that make it so unique and critical to both the communities and ecosystem it serves.

Research Manager for the Edwards Aquifer Authority’s Aquifer Science and Modeling Team, Brent Doty is a geoscientist with more than 16 years of experience in hydrogeology and water resources management. Brent is a licensed professional geoscientist in Texas and holds an M.S. in Natural Resources Management and a graduate certificate in Water Conflict Management and Transformation from Oregon State University.

Brent’s role includes the development and execution of several research initiatives to better understand the Edwards Aquifer System and to provide decision makers with the best available science to manage, enhance, and protect the Edwards Aquifer System. Brent has worked on several key initiatives, including surface and groundwater interactions, aquifer vulnerability assessments, and emerging contaminant studies. Much of his current work focuses on quantifying the potential benefits of nature-based land management solutions as a managed aquifer recharge project. Brent is also the lead geologist responsible for assessing potential conservation easement properties for the City of San Antonio’s Edwards Aquifer Protection Program, a 300 million-plus dollar conservation initiative that has protected more than 180,000 acres of environmentally sensitive land over the Edwards Aquifer Recharge and Contributing zones.

In his spare time, you can find Brent paddleboarding, hiking, or mountain biking across the beautiful Texas Hill Country.

If you are attending in person, there is no need to register. However, if you are attending via Zoom, please register here before the meeting begins as late registration and entry will not be allowed. After registering, you will receive a confirmation email containing information about joining the meeting.

Note: The Zoom recording will be available within days after the meeting on our  YouTube channel.

About the Region

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Salado, the location of our Fall 2025 Symposium, lies at the intersection of two ecoregions: the Edwards Plateau (Limestone Cut Plain) and Blackland Prairie (Northern Blackland Prairie).

The Edwards Plateau area is also called the Hill Country; however, this general term covers a much larger area extending farther north. Spring-fed creeks are found throughout the region; deep limestone canyons, rivers, and lakes (reservoirs) are common. Ashe juniper is perhaps the most common woody species found throughout the region. Additional woody species include various species of oak, with live oak (Quercus fusiformis) being the most common. Sycamores (Platanus occidentalis) and bald cypress (Taxodium distichum) border waterways. This area is well known for its spring wildflower displays, though they may be viewed in spring, late summer, and fall, as well. According to Texas Parks and Wildlife, average annual rainfall in the Edwards Plateau ranges from 15 to 34 inches.

The Blackland Prairie extends from the Red River south to San Antonio, bordered on the west by the Edwards Plateau and the Cross Timbers, and on the east by the Post Oak Savannah. Annual rainfall averages 30 to 40 inches, with higher averages to the east. This region is dominated by prairie species. The most common grass species include little bluestem (Schizachyrium scoparium) and Indian grass (Sorghastrum nutans) in the uplands and switchgrass (Panicum virgatum) in the riparian areas and drainages. Common herbaceous flowering plants include salvias, penstemons, and silphiums. This area has suffered greatly from overgrazing and agricultural use. Few intact areas remain, though many of the plants can be found along county roadsides throughout the region.

Our four host chapters (New Braunfels, Lindheimer, Guadalupe, and the Hill Country chapters) are located in one or both of the ecoregions above. However, the eastern portion of Guadalupe County also falls within the Post Oak Savanna ecoregion. Annual rainfall averages 35 to 45 inches, with higher averages to the east. A wide variety of hardwood trees are found, including several species of oaks, elms, and in the Bastrop area, loblolly pine (Pinus taeda). Grasses and forbs dominate in the open savannas, with most common grass being little bluestem. Ranching, agriculture, and fire suppression have allowed woody species to encroach on the once-open savannas.

Source: Wildflowers of Texas by Michael Eason