Peer-Reviewed Article
The Challenge of Supplying Sustainable Water to One of the Fastest Growing Metro Areas in the US Authors
Raul A. Deju, Ph.D., CPG-4025, (left) New Mexico Institute of Technology, Executive Chairman of the Board, Texas Water Supply Co., Boerne, Texas
and
Michael R. Thornhill M.S., PG, CPG-9545, (right) Oklahoma State University, President and Founder Thornhill Group, Inc., Austin, Texas.
Abstract
The 79-mile stretch of Interstate Highway 35 in Texas from San Antonio to Austin is the transportation artery for one of the fastest-growing employment and population growth areas in the US. Although somewhat behind Austin, San Antonio’s STEM (Science, Technology, Engineering and Mathematics) percent job growth since 2001 is also greater than that of all other Texas cities, and indeed it is three times the national average. Such high-end, technology-based employment has brought pressure to provide water resources for the accompanying growth in population. Many municipalities and water entities currently supply water in the area – primarily from reservoirs in the Austin metropolitan area, and mostly from wells and imported groundwater in San Antonio. San Antonio also imports water from brackish groundwater areas and utilizes aquifer storage and recovery (ASR). The areas between Austin and San Antonio also face critical challenges in keeping up with growing water-supply demands. Currently, these suburban areas rely on a myriad of wells and smaller reservoirs which are susceptible to effects of drought periods as well as collapse. Additional water supplies in the growth corridor between San Antonio and Austin must be developed in parallel with the population growth needs, and the water resources must be implemented and managed in sustainable and environmentally conscious manners.
The complex and varied geology within parts of northern Bexar and southern Comal counties provide a unique setting for developing relatively large, reliable groundwater supplies from the Middle Trinity aquifer. As a result of our compre- hensive hydrologic testing, mathematical modeling and comparison with the geohydrology of other neighboring areas we were able to determine that depth, thickness, recharge setting, faulting and karst development, and aquifer hydraulics (i.e., productivity ) for the Middle Trinity are generally more favorable in the subject well field area than in other highly populated areas such as Hays and western Travis counties. The initial well field consists of 20 wells with pumping rates ranging up to 2,250 gallons per minute (gpm) and specific capacity values of as high as 140 gallons per minute per foot (gpm/ft). We know of no larger or more productive well field in Central Texas. Production testing of the well fields, real- time monitoring systems data, numerical modeling with the state-approved groundwater flow model, available geologic and hydrologic information, and a favorable regulatory framework all indicate that the targeted supplies can be reliably provided long-term. This paper addresses some important considerations that use the existing data and models for the region to present a rational and cost-effective approach to ensure that water supply needs for the area are met over the next few decades.
Introduction: Water Supply in the Austin-San Antonio Corridor
The Texas Water Development Board (TWDB) projection is that the thirteen counties that comprising the Austin-San Antonio corridor will increase their combined population from a current estimate of 4.5 million (2018) to 5.8 million or more by 2030. Figure 1 shows the area encompassed by the San Antonio to Austin Corridor including Bexar, Comal, Kendall and Guadalupe counties to the south, Hays, Blanco and Caldwell counties in the middle, and Travis, Williamson, Bastrop, Lee, Milam and Burleson counties in the northern part of the growth area.
Just as in California’s Silicon Valley, this Central Texas
corridor is creating an identity of its own while retaining the identity of the two cities that anchor the growth, namely San Antonio in Bexar County and Austin in Travis County. It will truly be a high-tech corridor that will blend good jobs with a combination of rural and city-living in a great climate. The 1.3 million in population growth projected over the next 12 years will create an enormous need for construction of homes and supply of water, electricity, services, hospitals, and schools. The anchor cities of Austin and San Antonio are about 79 miles apart and are connected by excellent roads to anchor further expansion. The growth will create dormitory communities and business hubs in all surrounding counties. Counties in between San Antonio and Austin which today are primarily rural will most likely skyrocket their population.
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